Found 31 papers in cond-mat Two-dimensional materials (2DMs) are fundamentally electro-mechanical
systems. Their environment unavoidably strains them and modifies their quantum
transport properties. For instance, a simple uniaxial strain could completely
turn off the conductivity of ballistic graphene or switch on/off the
superconducting phase of magic-angle bilayer graphene. Here we report
measurements of quantum transport in strained graphene which agree
quantitatively with models based on mechanically-induced gauge potentials. We
mechanically induce in-situ a scalar potential, which modifies graphene's work
function by up to 25 meV, and vector potentials which suppress the ballistic
conductivity of graphene by up to 30 % and control its quantum interferences.
To do so, we developed an experimental platform able to precisely tune both the
mechanics and electrostatics of suspended graphene transistors at
low-temperature over a broad range of strain (up to 2.6 %). This work opens
many opportunities to experimentally explore quantitative strain effects in 2DM
quantum transport and technologies.
Inducing superconductivity in systems with unconventional band structures is
a promising approach for realising unconventional superconductivity. Of
particular interest are single interface or Josephson Junction architectures
involving Weyl semimetals, which are predicted to host odd parity, potentially
topological, superconducting states. These expectations rely crucially on the
tunneling of electronic states at the interface between the two systems. In
this study, we revisit the question of induced superconductivity in an
inversion broken WSM via quantum tunneling, treating the interface as an
effective potential barrier. We determine the conditions under which the gap
function couples to the Weyl physics and its properties within the WSM. Our
simulations show that the mismatch in the nature of the low energy electronic
states leads to a rapid decay of the superconductivity within the semi-metal.
In the $R$Al(Si,Ge) ($R$: lanthanides) family, both spatial inversion and
time-reversal symmetries are broken. This may offer opportunities to study
Weyl-fermion physics in nontrivial spin structures emerging from a
noncentrosymmetric crystal structure. In this study, we investigated the
anomalous Hall effect (AHE) in NdAlGe via magnetotransport, magnetization, and
magnetic torque measurements down to 40 mK (0.4 K for magnetization). The
single crystals grown by a laser-heated floating-zone method exhibit a single
magnetic phase transition at $T_{\rm M}$ = 13.5 K, where the $T_{\rm M}$ is the
transition temperature. With the magnetic field parallel to the easy
$\lbrack$001$\rbrack$ axis, the AHE gradually evolves as the temperature
decreases below $T_{\rm M}$. The anomalous Hall conductivity (AHC) reaches
$\sim$320 $\Omega^{-1}$cm$^{-1}$ at 40 mK in the magnetically saturated state.
Except in low-temperature low-field plateau phases, the AHC and magnetization
are proportional, and their ratio agrees with the ratios for conventional
ferromagnets, suggesting that the intrinsic AHE occurs by the Karplus-Luttinger
mechanism. Below $\sim$0.6 K, the curves of Hall resistivity against the field
exhibit plateaus at low fields below $\sim$0.5 T, correlating with the plateaus
in the magnetization curve. For the first plateau, the magnetization is one
order of magnitude smaller than the magnetically saturated state, whereas the
AHE is more than half that in the saturated state. This finding under well
below $T_{\rm M}$ suggests that the AHE at the first plateau is not governed by
the magnetization and may be interpreted based on a multipole or spin
chirality.
The intriguing interplay between topology and superconductivity has attracted
significant attention, given its potential for realizing topological
superconductivity. In this study, we investigate the transport properties of
the chiral Josephson effect in the quantum anomalous Hall insulators
(QAHIs)-based junction. We reveal a systematic crossover from edge-state to
bulk-state dominant supercurrents, with a notable $0-\pi$ transition observed
under non-zero magnetic flux through chemical potential adjustments. This
transition underscores the competition between bulk and chiral edge transport.
Furthermore, we identify an evolution among three distinct quantum interference
patterns: from a $2\Phi_0$-periodic oscillation pattern, to a $\Phi_0$-periodic
oscillation pattern, and then to an asymmetric Fraunhofer pattern ($\Phi_0 =
h/2e$ is the flux quantum, $h$ the Planck constant, and $e$ the electron
charge). Subsequently, we examine the influence of domains on quantum
interference patterns. Intriguingly, a distinctive Fraunhofer-like pattern
emerges due to coexistence of chiral edge states and domain wall states, even
when the chemical potential is within gap. These results not only advance the
theoretical understanding but also pave the way for the experimental discovery
of the chiral Josephson effect based on QAHI doped with magnetic impurities.
The coexistence of edge states and skin effects provides the topologically
protected localized states at the corners of two-dimensional systems. In this
paper, we realize such corner states in the two-dimensional
Su-Schrieffer-Heeger model with the nonreciprocal hoppings. For the
characterization of the real line gap topology, we introduce the $\mathbb{Z}_4$
Berry phase protected by generalized four-fold rotational symmetry. From the
physical picture of the adiabatic connection, we find that the value of the
$\mathbb{Z}_4$ Berry predicts the position of edge states. Additionally, by
using the winding number, we characterize the point gap topology of the edge
spectra. From the results of these characterizations by the first-order
topological invariants, we find that the pair of values of the $\mathbb{Z}_4$
Berry phase and the winging number yields the position of the topologically
protected localized states.
Electronic transport in monolayer MoS2 is significantly constrained by
several extrinsic factors despite showing good prospects as a transistor
channel material. Our paper aims to unveil the underlying mechanisms of the
electrical and magneto-transport in monolayer MoS2. In order to quantitatively
interpret the magneto-transport behavior of monolayer MoS2 on different
substrate materials, identify the underlying bottlenecks, and provide
guidelines for subsequent improvements, we present a deep analysis of the
magneto-transport properties in the diffusive limit. Our calculations are
performed on suspended monolayer MoS2 and MoS2 on different substrate materials
taking into account remote impurity and the intrinsic and extrinsic phonon
scattering mechanisms. We calculate the crucial transport parameters such as
the Hall mobility, the conductivity tensor elements, the Hall factor, and the
magnetoresistance over a wide range of temperatures, carrier concentrations,
and magnetic fields. The Hall factor being a key quantity for calculating the
carrier concentration and drift mobility, we show that for suspended monolayer
MoS2 at room temperature, the Hall factor value is around 1.43 for magnetic
fields ranging from 0.001 to 1 Tesla, which deviates significantly from the
usual value of unity. In contrast, the Hall factor for various substrates
approaches the ideal value of unity and remains stable in response to the
magnetic field and temperature. We also show that the MoS2 over an Al2O3
substrate is a good choice for the Hall effect detector. Moreover, the
magnetoresistance increases with an increase in magnetic field strength for
smaller magnetic fields before reaching saturation at higher magnetic fields.
The presented theoretical model quantitatively captures the scaling of mobility
and various magnetoresistance coefficients with temperature, carrier densities
and magnetic fields.
The realization of magnetic skyrmions in two-dimensional (2D) magnets holds
great promise for both fundamental research and device applications. Despite
recent progress, two-dimensional skyrmion hosts are still limited, due to the
fact that most 2D magnets are centrosymmetric and thus lack
Dzyaloshinskii-Moriya interaction (DMI). We show here, using a general analysis
based on symmetry, that Bloch-type skyrmions can, in fact, be stabilized in 2D
magnets, due to the interplay between in-plane component (dx) of second
nearest-neighbor DMI and magnetic anisotropy. Its validity is demonstrated in
the Cr2Ge2Te6 monolayer, which is also verified by recent experiments. Our work
gives a clear direction for experimental studies of 2D magnetic materials to
stabilize skyrmions and should greatly enrich the research on magnetic
skyrmions in 2D lattices.
We provide a comprehensive analysis of the prominent tight-binding (TB)
models for transition metal dichalcogenides (TMDs) available in the literature.
We inspect the construction of these TB models, discuss their parameterization
used and conduct a thorough comparison of their effectiveness in capturing
important electronic properties. Based on these insights, we propose a novel TB
model for TMDs designed for enhanced computational efficiency. Utilizing
$MoS_2$ as a representative case, we explain why specific models offer a more
accurate description. Our primary aim is to assist researchers in choosing the
most appropriate TB model for their calculations on TMDs.
Using angle-resolved photoemission spectroscopy (ARPES) and density
functional theory (DFT) calculations, we systematically studied the electronic
band structure of Mn$_3$Ge in the vicinity of the Fermi level. We observe
several bands crossing the Fermi level, confirming the metallic nature of the
studied system. We further observe several flat bands along various high
symmetry directions, consistent with the DFT calculations. The calculated
partial density of states (PDOS) suggests a dominant Mn $3d$ orbital
contribution to the total valence band DOS. With the help of orbital-resolved
band structure calculations, we qualitatively identify the orbital information
of the experimentally obtained band dispersions. Out-of-plane electronic band
dispersions are explored by measuring the ARPES data at various photon
energies. Importantly, our study suggests relatively weaker electronic
correlations in Mn$_3$Ge compared to Mn$_3$Sn.
Placing and twisting graphene on transition metal dichalcogenides (TMDC)
forms a van der Waals (vdW) heterostructure. The occurrence of Zeeman splitting
and Rashba spin-orbit coupling (SOC) changes graphene's linear dispersion and
conductivity. Hence, this paper studies the dependence of graphene's
longitudinal optical conductivity on Rashba SOC, the twist-angle and
temperature. At zero temperature, a main conductivity peak exists. When Rashba
SOC increases, a second peak occurs, with both extremes presenting an enhanced
height and width, and the frequencies where the two peaks arise will increase
because the energy gap and the possibility of electron transition increase.
Altering the twist-angle from 0 to 30$^{\circ}$, the conductivity is primarily
affected by chalcogen atoms. Moreover, when temperature increases to room
temperature, besides a Drude peak due to the thermal excitation, a new band
arises in the conductivity owing to the joint effect of the thermal transition
and the photon transition.
This paper presents an ab initio methodology to account for electron-phonon
interactions in 2D materials, focusing on transition metal dichalcogenides
(TMDCs). It combines density functional theory and maximally localized Wannier
functions to acquire material data and relies on the linearized Boltzmann
transport equation (LBTE) and the non-equilibrium Green's functions (NEGF)
method to determine the transport properties of materials and devices,
respectively. It is shown that for MoS$_2$, both LBTE and NEGF return very
close mobility values, without the need to adjust any parameter. The excellent
agreement between both approaches results from the inclusion of non-diagonal
entries in the electron-phonon scattering self-energies. The NEGF solver is
then used to shed light on the "current vs. voltage" characteristics of a
monolayer MoS$_2$ transistor, highlighting how the interactions with phonons
impact both the current magnitude and its distribution. The mobility of other
TMDCs is considered as well, demonstrating the capabilities of the proposed
technique to assess the potential of 2D channel materials in next-generation
logic applications.
Quantum teleportation can be used to define a notion of parallel transport
which characterizes the entanglement structure of a quantum state
\cite{Czech:2018kvg}. This suggests one can formulate a gauge theory of
entanglement. In \cite{Wong:2022mnv}, it was explained that measurement based
quantum computation in one dimension can be understood in term of such a gauge
theory (MBQC). In this work, we give an alternative formulation of this
"entanglement gauge theory" as an extended topological field theory. This
formulation gives a alternative perspective on the relation between the circuit
model and MBQC. In addition, it provides an interpretation of MBQC in terms of
the extended Hilbert space construction in gauge theories, in which the
entanglement edge modes play the role of the logical qubit.
Fractional Chern insulators (FCI) were proposed theoretically about a decade
ago. These exotic states of matter are fractional quantum Hall states realized
when a nearly flat Chern band is partially filled, even in the absence of an
external magnetic field. Recently, exciting experimental signatures of such
states have been reported in twisted MoTe$_2$ bilayer systems. Motivated by
these experimental and theoretical progresses, in this paper, we develop a
projective construction for the composite fermion states (either the Jain's
sequence or the composite Fermi liquid) in a partially filled Chern band with
Chern number $C=\pm1$, which is capable of capturing the microscopics, e.g.,
symmetry fractionalization patterns and magnetoroton excitations. On the
mean-field level, the ground states' and excitated states' composite fermion
wavefunctions are found self-consistently in an enlarged Hilbert space. Beyond
the mean-field, these wavefunctions can be projected back to the physical
Hilbert space to construct the electronic wavefunctions, allowing direct
comparison with FCI states from exact diagonalization on finite lattices. We
find that the projected electronic wavefunction corresponds to the
\emph{combinatorial hyperdeterminant} of a tensor. When applied to the
traditional Galilean invariant Landau level context, the present construction
exactly reproduces Jain's composite fermion wavefunctions. We apply this
projective construction to the twisted bilayer MoTe$_2$ system. Experimentally
relevant properties are computed, such as the magnetoroton band structures and
quantum numbers.
We study the topological properties of the Haldane and modified Haldane
models in $\alpha$-$T_{3}$ lattice. The band structures and phase diagrams of
the system are investigated. Individually, each model undergoes a distinct
phase transition: (i) The Haldane-only model experiences a topological phase
transition from the Chern insulator ($\mathcal{C} = 1$) phase to the higher
Chern insulator ($\mathcal{C} = 2$) phase; while (ii) the modified-Haldane-only
model experiences a phase transition from the topological metal ($\mathcal{C} =
2$) phase to the higher Chern insulator ($\mathcal{C} = 2$) phase and we show
that $\mathcal{C}$ is insufficient to characterize this system because
$\mathcal{C}$ remains unchanged before and after the phase transition. By
plotting the Chern number and $\mathcal{C}$ phase diagram, we show that in the
presence of both Haldane and modified Haldane models in the $\alpha$-$T_{3}$
lattice, the interplay between the two models manifests three distinct
topological phases, namely the $\mathcal{C} = 1$ Chern insulator (CI) phase,
$\mathcal{C} = 2$ higher Chern insulator (HCI) phase and $\mathcal{C} = 2$
topological metal (TM) phase. These results are further supported by the
$\alpha$-$T_{3}$ zigzag edge states calculations.
The electro-osmotic flow (EOF) in a neutral system consisting of an aqueous
NaCl solution confined in a nanochannel with two parallel Molybdenum disulfide
($\textrm{MoS}_{\textrm{2}}$) walls and in the presence of an external electric
field parallel to the channel walls, is investigated for the first time. The
results indicate that the thickness of the Stern layer grows as the negative
electric surface charge density on the nanochannel walls increases. The Stern
layer becomes thinner as the salt concentration is increased. Moreover, the EOF
occurs under the no-slip condition on the walls. In addition, by increasing the
surface charge density the average of the flow velocity across the nanochannel
initially grows (Debye--H$\ddot{\textrm{u}}$ckel regime) and reaches its
maximum value. Then, by further increasing the surface charge density the water
flow rate decreases (intermediate regime), and gets the zero value and becomes
negative (reverse flow regime) at even larger values of the surface charge
densities. Comparing the results of the previous work wherein the channels are
composed of the black phosphorene walls with those of the present study for a
channel composed of $\textrm{MoS}_{\textrm{2}}$ surfaces, show that for the
latter case the reverse flow occurs at a lower surface charge density and with
a greater value of the peak velocity with respect to the change in the surface
charge density for the former case.
The search for topological excitations such as Majorana fermions has spurred
interest in the boundaries between distinct quantum states. Here, we explore an
interface between two prototypical phases of electrons with conceptually
different ground states: the integer quantum Hall insulator and the s-wave
superconductor. We find clear signatures of hybridized electron and hole states
similar to chiral Majorana fermions, to which we refer as chiral Andreev edge
states (CAES). They propagate along the interface in the direction determined
by magnetic field and their interference can turn an incoming electron into an
outgoing electron or a hole, depending on the phase accumulated by the CAES
along their path. Our results demonstrate that these excitations can propagate
and interfere over a significant length, opening future possibilities for their
coherent manipulation.
Weyl points are generic and stable features in the energy spectrum of
Hamiltonians that depend on a three-dimensional parameter space. Non-generic
isolated two-fold degeneracy points, such as multi-Weyl points, split into Weyl
points upon a generic perturbation that removes the fine-tuning or protecting
symmetry. The number of the resulting Weyl points is at least $|Q|$, where $Q$
is the topological charge associated to the non-generic degeneracy point. Here,
we show that such a non-generic degeneracy point also has a birth quota, i.e.,
a maximum number of Weyl points that can be born from it upon any perturbation.
The birth quota is a local multiplicity associated to the non-generic
degeneracy point, an invariant of map germs known from singularity theory. This
holds not only for the case of a three-dimensional parameter space with a
Hermitian Hamiltonian, but also for the case of a two-dimensional parameter
space with a chiral-symmetric Hamiltonian. We illustrate the power of this
result for electronic band structures of two- and three-dimensional crystals.
Our work establishes a strong connection between singularity theory and
topological band structures, and more broadly, parameter-dependent quantum
systems.
The vanishing band gap of graphene has long presented challenges for making
high-quality quantum point contacts (QPCs) -- the partially transparent p-n
interfaces introduced by conventional split-gates tend to short the QPC. This
complication has hindered the fabrication of graphene quantum Hall
Fabry-P\'erot interferometers, until recent advances have allowed split-gate
QPCs to operate utilizing the highly resistive $\nu=0$ state. Here, we present
a simple recipe to fabricate QPCs by etching a narrow trench in the graphene
sheet to separate the conducting channel from self-aligned graphene side gates.
We demonstrate operation of the individual QPCs in the quantum Hall regime, and
further utilize these QPCs to create and study a quantum Hall interferometer.
We perform a systematic study of Andreev conversion at the interface between
a superconductor and graphene in the quantum Hall (QH) regime. We find that the
probability of Andreev conversion from electrons to holes follows an unexpected
but clear trend: the dependencies on temperature and magnetic field are nearly
decoupled. We discuss these trends and the role of the superconducting
vortices, whose normal cores could both absorb and dephase the individual
electrons in a QH edge. Our study may pave the road to engineering future
generation of hybrid devices for exploiting superconductivity proximity in
chiral channels.
We report $\beta$-detected nuclear magnetic resonance of ultra-dilute
$^{8}$Li$^{+}$ implanted in highly oriented pyrolytic graphite (HOPG). The
absence of motional narrowing and diffusional spin-lattice relaxation implies
Li$^+$ is not appreciably mobile up to 400 K, in sharp contrast to the highly
lithiated stage compounds. However, the relaxation is remarkably fast and
persists down to cryogenic temperatures. Ruling out extrinsic paramagnetic
impurities and intrinsic ferromagnetism, we conclude the relaxation is due to
paramagnetic centers correlated with implantation. While the resulting effects
are not consistent with a Kondo impurity, they also differ from free
paramagnetic centers, and we suggest that a resonant scattering approach may
account for much of the observed phenomenology.
The tensor functor called $\alpha$-induction arises from a Frobenius algebra
object, or a Q-system, in a braided unitary fusion category. In the operator
algebraic language, it gives extensions of endomorphism of $N$ to $M$ arising
from a subfactor $N\subset M$ of finite index and finite depth giving a braided
fusion category of endomorpshisms of $N$. It is also understood in terms of
Ocneanu's graphical calculus. We study this $\alpha$-induction for bi-unitary
connections, which give a characterization of finite-dimensional nondegenerate
commuting squares and gives certain 4-tensors appearing in recent studies of
2-dimensional topological order. We show that the resulting $\alpha$-induced
bi-unitary connections are flat if we have a commutative Frobenius algebra, or
a local Q-system. Examples related to chiral conformal field theory and the
Dynkin diagrams are presented.
How multiple observables mutually influence their dynamics has been a crucial
issue in statistical mechanics. We introduce a new concept, "quantum velocity
limits," to establish a quantitative and rigorous theory for non-equilibrium
quantum dynamics for multiple observables. Quantum velocity limits are
universal inequalities for a vector the describes velocities of multiple
observables. They elucidate that the speed of an observable of our interest can
be tighter bounded when we have knowledge of other observables, such as
experimentally accessible ones or conserved quantities, compared with the
conventional speed limits for a single observable. We first derive an
information-theoretical velocity limit in terms of the generalized correlation
matrix of the observables and the quantum Fisher information. The velocity
limit has various novel consequences: (i) conservation law in the system, a
fundamental ingredient of quantum dynamics, can improve the velocity limits
through the correlation between the observables and conserved quantities; (ii)
speed of an observable can be bounded by a nontrivial lower bound from the
information on another observable; (iii) there exists a notable non-equilibrium
tradeoff relation, stating that speeds of uncorrelated observables, e.g.,
anti-commuting observables, cannot be simultaneously large; (iv) velocity
limits for any observables on a local subsystem in locally interacting
many-body systems remain convergent even in the thermodynamic limit. Moreover,
we discover another distinct velocity limit for multiple observables on the
basis of the local conservation law of probability current, which becomes
advantageous for macroscopic transitions of multiple quantities.
Raman spectroscopy is widely used to assess the quality of 2D materials thin
films. This report focuses on $\rm{PtSe_2}$, a noble transition metal
dichalcogenide which has the remarkable property to transit from a
semi-conductor to a semi-metal with increasing layer number. While
polycrystalline $\rm{PtSe_2}$ can be grown with various crystalline qualities,
getting insight into the monocrystalline intrinsic properties remains
challenging. We report on the study of exfoliated 1 to 10 layers $\rm{PtSe_2}$
by Raman spectroscopy, featuring record linewidth. The clear Raman signatures
allow layer-thickness identification and provides a reference metrics to assess
crystal quality of grown films.
We discuss the generalization of the local renormalization group approach to
theories in which Weyl symmetry is gauged. These theories naturally correspond
to scale invariant - rather than conformal invariant - models in the flat space
limit. We argue that this generalization can be of use when discussing the
issue of scale vs conformal invariance in quantum and statistical field
theories. The application of Wess-Zumino consistency conditions constrains the
form of the Weyl anomaly and the beta functions in a nonperturbative way. In
this work we concentrate on two dimensional models including also the
contributions of the boundary. Our findings suggest that the renormalization
group flow between scale invariant theories differs from the one between
conformal theories because of the presence of a new charge that appears in the
anomaly. It does not seem to be possible to find a general scheme for which the
new charge is zero, unless the theory is conformal in flat space. Two
illustrative examples involving flat space's conformal and scale invariant
models that do not allow for a naive application of the standard local
treatment are given.
Earlier theoretical results on $p$-$d$ and $d$-$d$ exchange interactions for
zinc-blende semiconductors with Cr$^{2{+}}$ and Mn$^{3{+}}$ ions are revisited
and extended by including contributions beyond the dominating ferromagnetic
(FM) superexchange term [i.e., the interband Bloembergen-Rowland-Van Vleck
contribution and antiferromagnetic (AFM) two-electron term], and applied to
topological Cr-doped HgTe and non-topological (Zn,Cr)Te and (Ga,Mn)N in
zinc-blende and wurtzite crystallographic structures. From the obtained values
of the $d$-$d$ exchange integrals $J_{ij}$, and by combining the Monte-Carlo
simulations with the percolation theory for randomly distributed magnetic ions,
we determine magnitudes of Curie temperatures $T_{\text{C}}(x)$ for
$\mathrm{Zn}_{1-x}\mathrm{Cr}_x\mathrm{Te}$ and
$\mathrm{Ga}_{1-x}\mathrm{Mn}_x\mathrm{N}$ and compare to available
experimental data. Furthermore, we find that competition between FM and AFM
$d$-$d$ interactions can lead to a spin-glass phase in the case of
$\mathrm{Hg}_{1-x}\mathrm{Cr}_x\mathrm{Te}$. This competition, along with a
relatively large magnitude of the AF $p$-$d$ exchange energy $N_0\beta$ can
stabilize the quantum spin Hall effect, but may require the application of a
tilted magnetic field to observe the quantum anomalous Hall effect in HgTe
quantum wells doped with Cr.
We discuss two-dimensional conformal field theories (CFTs) which are
invariant under gauging a non-invertible global symmetry. At every point on the
orbifold branch of $c=1$ CFTs, it is known that the theory is self-dual under
gauging a $\mathbb{Z}_2\times \mathbb{Z}_2$ symmetry, and has
$\mathsf{Rep}(H_8)$ and $\mathsf{Rep}(D_8)$ fusion category symmetries as a
result. We find that gauging the entire $\mathsf{Rep}(H_8)$ fusion category
symmetry maps the orbifold theory at radius $R$ to that at radius $2/R$. At
$R=\sqrt{2}$, which corresponds to two decoupled Ising CFTs (Ising$^2$ in
short), the theory is self-dual under gauging the $\mathsf{Rep}(H_8)$ symmetry.
This implies the existence of a topological defect line in the Ising$^2$ CFT
obtained from half-space gauging of the $\mathsf{Rep}(H_8)$ symmetry, which
commutes with the $c=1$ Virasoro algebra but does not preserve the fully
extended chiral algebra. We bootstrap its action on the $c=1$ Virasoro primary
operators, and find that there are no relevant or marginal operators preserving
it. Mathematically, the new topological line combines with the
$\mathsf{Rep}(H_8)$ symmetry to form a bigger fusion category which is a
$\mathbb{Z}_2$-extension of $\mathsf{Rep}(H_8)$. We solve the pentagon
equations including the additional topological line and find 8 solutions, where
two of them are realized in the Ising$^2$ CFT. Finally, we show that the torus
partition functions of the Monster$^2$ CFT and Ising$\times$Monster CFT are
also invariant under gauging the $\mathsf{Rep}(H_8)$ symmetry.
We study the logarithmic entanglement negativity of symmetry-protected
topological (SPT) phases and quantum critical points (QCPs) of one-dimensional
noninteracting fermions at finite temperatures. In particular, we consider a
free fermion model that realizes not only quantum phase transitions between
gapped phases but also an exotic topological phase transition between quantum
critical states in the form of the fermionic Lifshitz transition. The bipartite
entanglement negativity between adjacent fermion blocks reveals the crossover
boundary of the quantum critical fan near the QCP between two gapped phases.
Along the critical phase boundary between the gapped phases, the sudden
decrease in the entanglement negativity signals the fermionic Lifshitz
transition responsible for the change in the topological nature of the QCPs. In
addition, the tripartite entanglement negativity between spatially separated
fermion blocks counts the number of topologically protected boundary modes for
both SPT phases and topologically nontrivial QCPs at zero temperature. However,
the long-distance entanglement between the boundary modes vanishes at finite
temperatures due to the instability of SPTs, the phases themselves.
Quantum field theory has various projective characteristics which are
captured by what are called anomalies. This paper explores this idea in the
context of fully-extended three-dimensional topological quantum field theories
(TQFTs).
Given a three-dimensional TQFT (valued in the Morita 3-category of fusion
categories), the anomaly identified herein is an obstruction to gauging a
naturally occurring orthogonal group of symmetries, i.e. we study 't Hooft
anomalies. In other words, the orthogonal group almost acts: There is a lack of
coherence at the top level. This lack of coherence is captured by a "higher
(central) extension" of the orthogonal group, obtained via a modification of
the obstruction theory of Etingof-Nikshych-Ostrik-Meir [ENO10]. This extension
tautologically acts on the given TQFT/fusion category, and this precisely
classifies a projective (equivalently anomalous) TQFT. We explain the sense in
which this is an analogue of the classical spin representation. This is an
instance of a phenomenon emphasized by Freed [Fre23]: Quantum theory is
projective.
In the appendices we establish a general relationship between the language of
projectivity/anomalies and the language of topological symmetries. We also
identify a universal anomaly associated with any theory which is appropriately
"simple".
We consider a nonequilibrium transition that leads to the formation of
nonlinear steady-state structures due to the gas flow scattering on a partially
penetrable obstacle. The resulting nonequilibrium steady state (NESS)
corresponds to a two-domain gas structure attained at certain critical
parameters. We use a simple mean-field model of the driven lattice gas with
ring topology to demonstrate that this transition is accompanied by the
emergence of local invariants related to a complex composed of the obstacle and
its nearest gas surrounding, which we refer to as obstacle edges. These
invariants are independent of the main system parameters and behave as local
first integrals, at least qualitatively. As a result, the complex becomes
insensitive to the noise of external driving field within the overcritical
domain. The emerged invariants describe the conservation of the number of
particles inside the obstacle and strong temporal synchronization or
correlation of gas states at obstacle edges. Such synchronization guarantees
the equality to zero of the total edge current at any time. The robustness
against external drive fluctuations is shown to be accompanied by strong
spatial localization of induced gas fluctuations near the domain wall
separating the depleted and dense gas phases. Such a behavior can be associated
with nonequilibrium protection effect and synchronization of edges. The
transition rates between different NESSs are shown to be different. The
relaxation rates from one NESS to another take complex and real values in the
sub- and overcritical regimes, respectively. The mechanism of these transitions
is governed by the generation of shock waves at the back side of the obstacle.
In the subcritical regime, these solitary waves are generated sequentially many
times, while only a single excitation is sufficient to rearrange the system
state in the overcritical regime.
We consider magnetic Weyl semimetals. First of all we review relation of
intrinsic anomalous Hall conductivity, band contribution to intrinsic magnetic
moment, and the conductivity of chiral separation effect (CSE) to the
topological invariants written in terms of the Wigner transformed Green
functions (with effects of interaction and disorder taken into account). Next,
we concentrate on the CSE. The corresponding bulk axial current would result in
accumulation of particles and holes of opposite chiralities at the surface of
the sample. However, this accumulation is compensated by the flow of the states
in momentum space along the Fermi arcs. Together with the bulk CSE current this
flow forms closed Weyl orbits. Their detection can be considered as
experimental discovery of chiral separation effect. Previously it was proposed
to detect Weyl orbits through the observation of quantum oscillations
\cite{Potter_2014} . We propose the alternative way to detect existence of Weyl
orbits through the observation of their contributions to Hall conductance.
We propose, and theoretically analyze, a practical protocol for the creation
of topological monopole configurations, quantum knots, and skyrmions in
Bose--Einstein condensates by employing fictitious magnetic fields induced by
the interaction of the atomic cloud with coherent light fields. It is observed
that a single coherent field is not enough for this purpose, but instead we
find incoherent superpositions of several coherent fields that introduce
topological point charges. We numerically estimate the experimentally
achievable strengths and gradients of the induced fictitious magnetic fields
and find them to be adjustable at will to several orders of magnitude greater
than those of the physical magnetic fields employed in previous experimental
studies. This property together with ultrafast control of the optical fields
paves the way for advanced engineering of topological defects in quantum gases.

Date of feed: Mon, 04 Dec 2023 01:30:00 GMT**Search terms: **(topolog[a-z]+)|(graphit[a-z]+)|(rhombohedr[a-z]+)|(graphe[a-z]+)|(chalcog[a-z]+)|(landau)|(weyl)|(dirac)|(STM)|(scan[a-z]+ tunne[a-z]+ micr[a-z]+)|(scan[a-z]+ tunne[a-z]+ spectr[a-z]+)|(scan[a-z]+ prob[a-z]+ micr[a-z]+)|(MoS.+\d+|MoS\d+)|(MoSe.+\d+|MoSe\d+)|(MoTe.+\d+|MoTe\d+)|(WS.+\d+|WS\d+)|(WSe.+\d+|WSe\d+)|(WTe.+\d+|WTe\d+)|(Bi\d+Rh\d+I\d+|Bi.+\d+.+Rh.+\d+.+I.+\d+.+)|(BiTeI)|(BiTeBr)|(BiTeCl)|(ZrTe5|ZrTe.+5)|(Pt2HgSe3|Pt.+2HgSe.+3)|(jacuting[a-z]+)|(flatband)|(flat.{1}band)|(LK.{1}99) **Mechanical control of quantum transport in graphene. (arXiv:2312.00177v1 [cond-mat.mes-hall])**

A. C. McRae, G. Wei, L. Huang, S. Yigen, V. Tayari, A. R. Champagne

**Proximity effect of s-wave superconductor on inversion broken Weyl Semi-Metal. (arXiv:2312.00187v1 [cond-mat.supr-con])**

Robert Dawson, Vivek Aji

**Anomalous Hall effect with plateaus observed in a magnetic Weyl semimetal NdAlGe at low temperatures. (arXiv:2312.00222v1 [cond-mat.str-el])**

Naoki Kikugawa, Shinya Uji, Taichi Terashima

**Effects of domain walls and chiral supercurrent in quantum anomalous Hall Josephson junctions. (arXiv:2312.00331v1 [cond-mat.mes-hall])**

Junjie Qi, Haiwen Liu, Jie Liu, Hua Jiang, Dong E. Liu, Chui-Zhen Chen, Ke He, X. C. Xie

**Hybrid Higher-Order Topological Skin Modes in the Two-Dimensional Su-Schrieffer-Heeger Model with Nonreciprocal Hoppings. (arXiv:2312.00371v1 [cond-mat.mes-hall])**

Hiromasa Wakao

**Magneto-transport in the monolayer MoS2 material system for high-performance field-effect transistor applications. (arXiv:2312.00378v1 [cond-mat.mes-hall])**

Anup Kumar Mandia, Rohit Kumar, Seung-Cheol Lee, Satadeep Bhattacharjee, Bhaskaran Muralidharan

**Unravelling spontaneous Bloch-type skyrmion in centrosymmetric two-dimensional magnets. (arXiv:2312.00423v1 [cond-mat.mtrl-sci])**

Jingman Pang, Xiaohang Niu, Hong Jian Zhao, Yun Zhang, Laurent Bellaiche

**Comparative Analysis of Tight-Binding models for Transition Metal Dichalcogenides. (arXiv:2312.00498v1 [cond-mat.mtrl-sci])**

Bert Jorissen, Lucian Covaci, Bart Partoens

**Weak Electronic Correlations Observed in Magnetic Weyl Semimetal Mn$_3$Ge. (arXiv:2312.00511v1 [cond-mat.mtrl-sci])**

Susmita Changdar, Susanta Ghosh, Anumita Bose, Indrani Kar, Achintya Low, Patrick Le Fevre, François Bertran, Awadhesh Narayan, Setti Thirupathaiah

**Longitudinal optical conductivity of graphene in van der Waals heterostructures composed of graphene and transition metal dichalcogenides. (arXiv:2312.00543v1 [cond-mat.mes-hall])**

Ruoyang Cui, Yaojin Li

**Phonon-Limited Transport in 2D Materials: A Unified Approach for ab initio Mobility and Current Calculations. (arXiv:2312.00577v1 [cond-mat.mes-hall])**

Jonathan Backman, Youseung Lee, Mathieu Luisier

**Edge modes, extended TQFT, and measurement based quantum computation. (arXiv:2312.00605v1 [hep-th])**

Gabriel Wong

**Hyperdeterminants and Composite fermion States in Fractional Chern Insulators. (arXiv:2312.00636v1 [cond-mat.str-el])**

Xiaodong Hu, Di Xiao, Ying Ran

**Interplay between Haldane and modified Haldane models in $\alpha$-$T_{3}$ lattice: Band structures, phase diagrams and edge states. (arXiv:2312.00642v1 [cond-mat.str-el])**

Kok Wai Lee, Pei-Hao Fu, Yee Sin Ang

**Molecular Dynamics Study of Electro-Osmotic Flow in a Nanochannel with Molybdenum Disulfide Walls. (arXiv:2312.00767v1 [cond-mat.soft])**

S.M.Kazem Manzoorolajdad, Hossein Hamzehpour, Jalal Sarabadani

**Interference of chiral Andreev edge states. (arXiv:1907.01722v3 [cond-mat.mes-hall] UPDATED)**

Lingfei Zhao, Ethan G. Arnault, Alexey Bondarev, Andrew Seredinski, Trevyn Larson, Anne W. Draelos, Hengming Li, Kenji Watanabe, Takashi Taniguchi, François Amet, Harold U. Baranger, Gleb Finkelstein

**Birth Quota of Non-Generic Degeneracy Points. (arXiv:2202.05825v2 [cond-mat.mes-hall] UPDATED)**

Gergő Pintér, György Frank, Dániel Varjas, András Pályi

**Graphene-based quantum Hall interferometer with self-aligned side gates. (arXiv:2206.05623v2 [cond-mat.mes-hall] UPDATED)**

Lingfei Zhao, Ethan G. Arnault, Trevyn F. Q. Larson, Zubair Iftikhar, Andrew Seredinski, Tate Fleming, Kenji Watanabe, Takashi Taniguchi, Francois Amet, Gleb Finkelstein

**Loss and decoherence at the quantum Hall - superconductor interface. (arXiv:2210.04842v2 [cond-mat.mes-hall] UPDATED)**

Lingfei Zhao, Zubair Iftikhar, Trevyn F.Q. Larson, Ethan G. Arnault, Kenji Watanabe, Takashi Taniguchi, Francois Amet, Gleb Finkelstein

**Ion-Implanted $^8$Li Nuclear Magnetic Resonance in Highly Oriented Pyrolytic Graphite. (arXiv:2301.07821v4 [cond-mat.mtrl-sci] UPDATED)**

John O. Ticknor, Jonah R. Adelman, Aris Chatzichristos, Martin H. Dehn, Luca Egoriti, Derek Fujimoto, Victoria L. Karner, Robert F. Kiefl, C. D. Philip Levy, Ruohong Li, Ryan M. L. McFadden, Gerald D. Morris, Mohamed Oudah, Monika Stachura, Edward Thoeng, W. Andrew MacFarlane

**$\alpha$-induction for bi-unitary connections. (arXiv:2302.05577v3 [math.QA] UPDATED)**

Yasuyuki Kawahigashi

**Quantum Velocity Limits for Multiple Observables: Conservation Laws, Correlations, and Macroscopic Systems. (arXiv:2305.03190v3 [cond-mat.stat-mech] UPDATED)**

Ryusuke Hamazaki

**Raman Spectroscopy of Monolayer to Bulk PtSe2 Exfoliated Crystals. (arXiv:2307.15520v3 [cond-mat.mtrl-sci] UPDATED)**

Marin Tharrault, Eva Desgué, Dominique Carisetti, Bernard Plaçais, Christophe Voisin, Pierre Legagneux, Emmanuel Baudin

**Consequences of the gauging of Weyl symmetry and the two-dimensional conformal anomaly. (arXiv:2309.09598v2 [hep-th] UPDATED)**

Omar Zanusso

**Tight-binding theory of spin-spin interactions, Curie temperatures, and quantum Hall effects in topological (Hg,Cr)Te in comparison to non-topological (Zn,Cr)Te, and (Ga,Mn)N. (arXiv:2310.19856v2 [cond-mat.mtrl-sci] UPDATED)**

Cezary Śliwa, Tomasz Dietl

**Self-duality under gauging a non-invertible symmetry. (arXiv:2310.19867v2 [hep-th] UPDATED)**

Yichul Choi, Da-Chuan Lu, Zhengdi Sun

**Finite Temperature Entanglement Negativity of Fermionic Symmetry Protected Topological Phases and Quantum Critical Points in One Dimension. (arXiv:2310.20566v2 [cond-mat.str-el] UPDATED)**

Wonjune Choi, Michael Knap, Frank Pollmann

**Projective symmetries of three-dimensional TQFTs. (arXiv:2311.01637v2 [math.QA] UPDATED)**

Jackson Van Dyke

**Nonequilibrium protection effect and spatial localization of noise-induced fluctuations under gas flow scattering on partially penetrable obstacle. (arXiv:2311.11658v2 [cond-mat.stat-mech] UPDATED)**

S.P. Lukyanets, O.V. Kliushnichenko

**Weyl orbits as probe of chiral separation effect in magnetic Weyl semimetals. (arXiv:2311.12712v2 [cond-mat.mes-hall] UPDATED)**

M.A.Zubkov

**Optically Induced Monopoles, Knots, and Skyrmions in Quantum Gases. (arXiv:2311.15972v2 [cond-mat.quant-gas] UPDATED)**

Toni Annala, Tommi Mikkonen, Mikko Möttönen