Found 23 papers in cond-mat
Date of feed: Wed, 02 Aug 2023 00:30:00 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]+)

Large circular photocurrent in non-centrosymmetric magnetic Weyl semimetal CeAlSi. (arXiv:2308.00045v1 [cond-mat.mes-hall])
Abhirup Roy Karmakar, A. Taraphder, G. P. Das

CeAlSi has been recently identified as a Weyl semimetal with simultaneous breaking of inversion and time-reversal symmetries. Among many potential distinguishing features that this may offer, we focus on the nonlinear optical properties. We present a thorough examination of the injection current, associated with circular photogalvanic effect, from a first-principles approach. Our study demonstrates a significant injection current, exceeding previously reported results in literature. Interestingly, dominant contribution comes in the near-infrared region of the electromagnetic spectrum. In addition, we explored several externally adjustable parameters that may have a positive impact on the circular photocurrent. We uncover a substantial boost in the photocurrent through the application of uniaxial strain along c-axis of the crystal $-$ a 5% strain results in a remarkable 62% increment. This provides insight into the exceptional optoelectronic characteristics of CeAlSi and opens up potential avenues for novel photogalvanic applications.

MoS$_{2}$/Al$_{0.68}$Sc$_{0.32}$N negative capacitance field-effect transistors. (arXiv:2308.00067v1 [cond-mat.mtrl-sci])
Seunguk Song, Kwan-Ho Kim, Srikrishna Chakravarthi, Zirun Han, Gwangwoo Kim, Kyung Yeol Ma, Hyeon Suk Shin, Roy H. Olsson III, Deep Jariwala

Al$_{0.68}$Sc$_{0.32}$N (AlScN) has gained attention for its outstanding ferroelectric properties, including a high coercive field and high remnant polarization. Although AlScN-based ferroelectric field-effect transistors (FETs) for memory applications have been demonstrated, a device for logic applications with minimal hysteresis has not been reported. This study reports on the transport characteristics of a MoS$_{2}$ negative capacitance FET (NCFET) based on an AlScN ferroelectric material. We experimentally demonstrate the effect of a dielectric layer in the gate stack on the memory window and subthreshold swing (SS) of the NCFET. We show that the hysteresis behavior of transfer characteristics in the NCFET can be minimized with the inclusion of a non-ferroelectric dielectric layer, which fulfills the capacitance-matching condition. Remarkably, we also observe the NC effect in MoS$_{2}$/AlScN NCFETs arrays based on large-area monolayer MoS$_{2}$ synthesized by chemical vapor deposition, showing the SS values smaller than its thermionic limit (~36-60 mV/dec) and minimal variation in threshold voltages (< 20 mV).

Diverse universality classes of the topological deconfinement transitions of three-dimensional noncompact lattice Abelian-Higgs models. (arXiv:2308.00101v1 [cond-mat.stat-mech])
Claudio Bonati, Andrea Pelissetto, Ettore Vicari

We study the topological phase transitions occurring in three-dimensional (3D) multicomponent lattice Abelian-Higgs (LAH) models, in which an $N$-component scalar field is minimally coupled with a noncompact Abelian gauge field, with a global SU($N$) symmetry. Their phase diagram presents a high-temperature Coulomb (C) phase, and two low-temperature molecular (M) and Higgs (H) phases, both characterized by the spontaneous breaking of the SU($N$) symmetry. The molecular-Higgs (MH) and Coulomb-Higgs (CH) transitions are topological transitions, separating a phase with gapless gauge modes and confined charges from a phase with gapped gauge modes and deconfined charged excitations. These transitions are not described by effective Landau-Ginzburg-Wilson theories, due to the active role of the gauge modes. We show that the MH and CH transitions belong to different charged universality classes. The CH transitions are associated with the $N$-dependent charged fixed point of the renormalization-group (RG) flow of the 3D Abelian-Higgs field theory (AHFT). On the other hand, the universality class of the MH transitions is independent of $N$ and coincides with that controlling the continuous transitions of the one-component ($N=1$) LAH model. In particular, we verify that the gauge critical behavior always corresponds to that observed in the 3D inverted XY model, and that the correlations of an extended charged gauge-invariant operator (in the Lorenz gauge, this operator corresponds to the scalar field, thus it is local, justifing the use of the RG framework) have an $N$-independent critical universal behavior. This scenario is supported by numerical results for $N=1,\,2,\,25$. The MH critical behavior does not apparently have an interpretation in terms of the RG flow of the AHFT, as determined perturbatively close to four dimensions or with standard large-$N$ methods.

Doped 2D diamond: properties and applications. (arXiv:2308.00124v1 [cond-mat.mtrl-sci])
Bruno Ipaves, João F. Justo, Biplab Sanyal, Lucy V. C. Assali

In the present paper, we investigate the structural, thermodynamic, dynamic, elastic, and electronic properties of doped 2D diamond C$_4$X$_2$ (X = B or N) nanosheets in both AA$'$A$''$ and ABC stacking configurations, by first-principles calculations. Those systems are composed of 3 diamond-like graphene sheets, with an undoped graphene layer between two 50% doped ones. Our results, based on the analysis of ab-initio molecular dynamics simulations, phonon dispersion spectra, and Born's criteria for mechanical stability, revealed that all four structures are stable. Additionally, their standard enthalpy of formation values are similar to the one of pristine 2D diamond, recently synthesized by compressing three graphene layers. The C$_4$X$_2$ (X = B or N) systems exhibit high elastic constant values and stiffness comparable to the diamond. The C$_4$N$_2$ nanosheets present wide indirect band gaps that could be advantageous for applications similar to the ones of the hexagonal boron nitride (h-BN), such as a substrate for high-mobility 2D devices. On the other hand, the C$_4$B$_2$ systems are semiconductors with direct band gaps, in the 1.6 - 2.0 eV range, and small effective masses, which are characteristics that may be favorable to high carrier mobility and optoelectronics applications.

No Strings Attached: Boundaries and Defects in the Cubic Code. (arXiv:2308.00138v1 [quant-ph])
Cory T. Aitchison, Daniel Bulmash, Arpit Dua, Andrew C. Doherty, Dominic J. Williamson

Haah's cubic code is the prototypical type-II fracton topological order. It instantiates the no string-like operator property that underlies the favorable scaling of its code distance and logical energy barrier. Previously, the cubic code was only explored in translation-invariant systems on infinite and periodic lattices. In these settings, the code distance scales superlinearly with the linear system size, while the number of logical qubits within the degenerate ground space exhibits a complicated functional dependence that undergoes large fluctuations within a linear envelope. Here, we extend the cubic code to systems with open boundary conditions and crystal lattice defects. We characterize the condensation of topological excitations in the vicinity of these boundaries and defects, finding that their inclusion can introduce local string-like operators and enhance the mobility of otherwise fractonic excitations. Despite this, we use these boundaries and defects to define new encodings where the number of logical qubits scales linearly without fluctuations, and the code distance scales superlinearly, with the linear system size. These include a subsystem encoding with open boundary conditions and a subspace encoding using lattice defects.

Performance benchmarking of an ultra-low vibration laboratory to host a commercial millikelvin scanning tunnelling microscope. (arXiv:2308.00333v1 [cond-mat.supr-con])
Yande Que, Amit Kumar, Michael S. Lodge, Zhengjue Tong, Marcus Lai Kar Fai, Wei Tao, Zhenhao Cui, Ranjith Shivajirao, Junxiang Jia, Siew Eang Lee, Bent Weber

Ultra-low temperature scanning tunnelling microscopy and spectroscopy (STM/STS) achieved by dilution refrigeration can provide unrivalled insight into the local electronic structure of quantum materials and atomic-scale quantum systems. Effective isolation from mechanical vibration and acoustic noise is critical in order to achieve ultimate spatial and energy resolution. Here, we report on the design and performance of an ultra-low vibration (ULV) laboratory hosting a customized but otherwise commercially available 40mK STM. The design of the vibration isolation consists of a T-shaped concrete mass block (55t), suspended by actively controlled pneumatic springs, and placed on a foundation separated from the surrounding building in a "room-within-a-room" design. Vibration levels achieved are meeting the VC-M vibration standard at >3 Hz, reached only in a limited number of laboratories worldwide. Measurement of the STM's junction noise confirms effective vibration isolation on par with custom built STMs in ULV laboratories. In this tailored low-vibration environment, the STM achieves an energy resolution of 43ueV (144 mK), promising for the investigation and control of quantum matter at atomic length scales.

Local polar order controls mechanical stress and triggers layer formation in developing Myxococcus xanthus colonies. (arXiv:2308.00368v1 [cond-mat.soft])
Endao Han, Chenyi Fei, Ricard Alert, Katherine Copenhagen, Matthias D. Koch, Ned S. Wingreen, Joshua W. Shaevitz

Colonies of the social bacterium Myxococcus xanthus go through a morphological transition from a thin colony of cells to three-dimensional droplet-like fruiting bodies as a strategy to survive starvation. The biological pathways that control the decision to form a fruiting body have been studied extensively. However, the mechanical events that trigger the creation of multiple cell layers and give rise to droplet formation remain poorly understood. By measuring cell orientation, velocity, polarity, and force with cell-scale resolution, we reveal a stochastic local polar order in addition to the more obvious nematic order. Average cell velocity and active force at topological defects agree with predictions from active nematic theory, but their fluctuations are anomalously large due to polar active forces generated by the self-propelled rod-shaped cells. We find that M. xanthus cells adjust their reversal frequency to tune the magnitude of this local polar order, which in turn controls the mechanical stresses and triggers layer formation in the colonies.

CMOS on-chip thermometry at deep cryogenic temperatures. (arXiv:2308.00392v1 [])
Grayson M. Noah, Thomas Swift, Mathieu de Kruijf, Alberto Gomez-Saiz, John J. L. Morton, M. Fernando Gonzalez-Zalba

Accurate on-chip temperature sensing is critical for the optimal performance of modern CMOS integrated circuits (ICs), to understand and monitor localized heating around the chip during operation. The development of quantum computers has stimulated much interest in ICs operating a deep cryogenic temperatures (typically 0.01 - 4 K), in which the reduced thermal conductivity of silicon and silicon oxide, and the limited cooling power budgets make local on-chip temperature sensing even more important. Here, we report four different methods for on-chip temperature measurements native to complementary metal-oxide-semiconductor (CMOS) industrial fabrication processes. These include secondary and primary thermometry methods and cover conventional thermometry structures used at room temperature as well as methods exploiting phenomena which emerge at cryogenic temperatures, such as superconductivity and Coulomb blockade. We benchmark the sensitivity of the methods as a function of temperature and use them to measure local excess temperature produced by on-chip heating elements. Our results demonstrate thermometry methods that may be readily integrated in CMOS chips with operation from the milliKelivin range to room temperature.

Field-Emission Resonances in Thin Metallic Films: Nonexponential Decay of the Tunneling Current as a Function of the Sample-to-Tip Distance. (arXiv:2308.00418v1 [cond-mat.mes-hall])
A. Yu. Aladyshkin, K. Schouteden

Field-emission resonances (FERs) for two-dimensional Pb(111) islands grown on \mbox{Si(111)7$\times$7} surfaces were studied by low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) in a broad range of tunneling conditions with both active and disabled feedback loop. These FERs exist at quantized sample-to-tip distances $Z^{\,}_n$ above the sample surface, where $n$ is the serial number of the FER state. By recording the trajectory of the STM tip during ramping of the bias voltage $U$ (while keeping the tunneling current $I$ fixed), we obtain the set of the $Z^{\,}_n$ values corresponding to local maxima in the derived $dZ/dU(U)$ spectra. This way, the continuous evolution of $Z^{\,}_n$ as a function of $U$ for all FERs was investigated by STS experiments with active feedback loop for different $I$. Complementing these measurements by current-distance spectroscopy at a fixed $U$, we could construct a 4-dimensional $I-U-Z-dZ/dU$ diagram, that allows us to investigate the geometric localization of the FERs above the surface. We demonstrate that (i) the difference $\delta Z^{\,}_n=Z^{\,}_{n+1}-Z^{\,}_n$ between neighboring FER lines in the $Z-U$ diagram is independent of $n$ for higher resonances, (ii) the $\delta Z^{\,}_{n}$ value decreases as $U$ increases; (iii) the quantized FER states lead to the \emph{periodic} variations of $\ln I$ as a function of $Z$ with periodicity $\delta Z$; (iv) the periodic variations in the $\ln I - Z$ spectra allows to estimate the absolute height of the tip above the sample surface. Our findings contribute to a deeper understanding on how the FER states affect various types of tunneling spectroscopy experiments and how they lead to a non-exponential decay of the tunneling current as a function of $Z$ at high bias voltages in the regime of quantized electron emission.

Hydrostatic Pressure Induced Anomalous Enhancement in the Thermoelectric Performance of Monolayer MoS$_{2}$. (arXiv:2308.00423v1 [cond-mat.mtrl-sci])
Saumen Chaudhuri, Amrita Bhattacharya, A. K. Das, G. P. Das, B. N. Dev

The hydrostatic pressure induced changes in the transport properties of monolayer (ML) MoS$_2$ have been investigated using first-principles density functional theory based calculations. The application of pressure induces shift in the conduction band minimum (CBM) from K to $\Lambda$, while retaining the band extrema at K in around the same energy at a pressure of 10 GPa. This increase in valley degeneracy is found to have a significant impact on the electronic transport properties of ML-MoS$_2$ via enhancement of the thermopower (S) by up to 140\% and power factor (S$^{2}$$\sigma$/$\tau$) by up to 310\% at 300 K. Besides, the very low deformation potential (E$_\text{DP}$) associated with the CB-$\Lambda$ valley results in a remarkably high electronic mobility ($\mu$) and relaxation time ($\tau$). Additionally, the application of pressure reduces the room temperature lattice thermal conductivity ($\kappa_\text{L}$) by 20\% of its unstrained value, owing to the increased anharmonicity and resulting increase in the intrinsic phonon scattering rates. The hydrostatic pressure induced increase in power factor (S$^{2}$$\sigma$) and the decrease in $\kappa_\text{L}$ act in unison to result in a substantial improvement in the overall thermoelectric performance (zT) of ML-MoS$_2$. At 900 K with an external pressure of 25 GPa, zT values of 1.63 and 1.21 are obtained for electron and hole doping, respectively, which are significantly higher compared to the zT values at zero pressure. For the implementation in a thermoelectric module where both n-type and p-type legs should be preferably made of the same material, the concomitant increase in zT of ML-MoS$_2$ for both types of doping with hydrostatic pressure can be highly beneficial.

Electrical detection and nucleation of a magnetic skyrmion in a magnetic tunnel junction observed via operando magnetic microscopy. (arXiv:2308.00445v1 [cond-mat.mtrl-sci])
by J. Urrestarazu Larrañaga, Naveen Sisodia, Van Tuong Pham, Ilaria Di Manici, Aurélien Masseboeuf, Kevin Garello, Florian Disdier, Bruno Fernandez, Sebastian Wintz, Markus Weigand, Mohamed Belmeguenai, Stefania Pizzini, Ricardo Sousa, Liliana Buda-Prejbeanu, Gilles Gaudin, Olivier Boulle

Magnetic skyrmions are topological spin textures which are envisioned as nanometre scale information carriers in magnetic memory and logic devices. The recent demonstration of room temperature stabilization of skyrmions and their current induced manipulation in industry compatible ultrathin films were first steps towards the realisation of such devices. However, important challenges remain regarding the electrical detection and the low-power nucleation of skyrmions, which are required for the read and write operations. Here, we demonstrate, using operando magnetic microscopy experiments, the electrical detection of a single magnetic skyrmion in a magnetic tunnel junction (MTJ) and its nucleation and annihilation by gate voltage via voltage control of magnetic anisotropy. The nucleated skyrmion can be further manipulated by both gate voltage and external magnetic field, leading to tunable intermediate resistance states. Our results unambiguously demonstrate the readout and voltage controlled write operations in a single MTJ device, which is a major milestone for low power skyrmion based technologies.

A Platform for Far-Infrared Spectroscopy of Quantum Materials at Millikelvin Temperatures. (arXiv:2308.00610v1 [cond-mat.mes-hall])
Michael Onyszczak, Ayelet J. Uzan, Yue Tang, Pengjie Wang, Yanyu Jia, Guo Yu, Tiancheng Song, Ratnadwip Singha, Jason F. Khoury, Leslie M. Schoop, Sanfeng Wu

Optical spectroscopy of quantum materials at ultralow temperatures is rarely explored, yet it may provide critical characterizations of quantum phases not possible using other approaches. We describe the development of a novel experimental platform that enables optical spectroscopic studies, together with standard electronic transport, of materials at millikelvin temperatures inside a dilution refrigerator. The instrument is capable of measuring both bulk crystals and micron-sized two-dimensional van der Waals materials and devices. We demonstrate the performance by implementing photocurrent-based Fourier transform infrared spectroscopy on a monolayer WTe$_2$ device and a multilayer 1T-TaS$_2$ crystal, with a spectral range available from near-infrared to terahertz range and in magnetic fields up to 5 T. In the far-infrared regime, we achieve spectroscopic measurements at a base temperature as low as ~ 43 mK and a sample electron temperature of ~ 450 mK. Possible experiments and potential future upgrades of this versatile instrumental platform are envisioned.

Electronic structure of the putative room-temperature superconductor Pb$_9$Cu(PO$_4$)$_6$O. (arXiv:2308.00676v1 [cond-mat.supr-con])
Liang Si, Karsten Held

A recent paper [Lee {\em et al.}, J. Korean Cryt. Growth Cryst. Techn. {\bf 33}, 61 (2023)] provides some experimental indications that Pb$_{10-x}$Cu$_x$(PO$_4$)$_6$O with $x\approx 1$, coined LK-99, might be a room-temperature superconductor at ambient pressure. Our density-functional theory calculations show lattice parameters and a volume contraction with $x$ -- very similar to experiment. The DFT electronic structure shows Cu$^{2+}$ in a $3d^9$ configuration with two extremely flat Cu bands crossing the Fermi energy. This puts Pb$_{9}$Cu(PO$_4$)$_6$O in an ultra-correlated regime and suggests that, without doping, it is a Mott or charge transfer insulator. If doped such an electronic structure might support flat-band superconductivity or an correlation-enhanced electron-phonon mechanism, whereas a diamagnet without superconductivity appears to be rather at odds with our results.

On the vibrational properties of transition metal doped ZnO: surface, defect, and bandgap engineering. (arXiv:2308.00684v1 [cond-mat.mtrl-sci])
Viviane M. A. Lage, Carlos Rodríguez-Fernández, Felipe S. Vieira, Rafael T. da Silva, Maria Inês B. Bernardi, Maurício M de Lima Jr., Andrés Cantarero, Hugo B. de Carvalho

We present a comprehensive study on the structure and optical properties of Mn-and Co-doped ZnO samples prepared via solid-state reaction method with different dopant concentrations and atmospheres. The samples were structural and chemically characterized via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray excited photoelectron spectroscopy. The optical characterization was performed via Raman, photoluminescence, and diffuse photoreflectance spectroscopies. Emphasis was done on the studies of their vibrational properties. The structural data confirm the incorporation of Mn and Co ions into the wurtzite ZnO lattice. It is demonstrated that the usual observed additional bands in the Raman spectrum of transitional metal (TM) doped ZnO are related to structural damage, deriving from the doping process, and surface effects. The promoted surface optical phonons (SOP) are of Fr\"ohlich character and, together with the longitudinal optical (LO) polar phonons, are directly dependent on the ZnO electronic structure. The enhancement of SOP and LO modes with TM-doping is explained in terms of nonhomogeneous doping, with the dopants concentrating mainly on the surface of grains, and a resonance effect due to the decrease of the ZnO bandgap promoted by the introduction of the 3d TM levels within the ZnO bandgap. We also discuss the origin of the controversial vibrational mode commonly observed in the Mn-doped ZnO system. It is stated that the observation of the analyzed vibrational properties is a signature of substitutional doping of the ZnO structure with tuning of ZnO optical absorption into the visible range of the electromagnetic spectrum.

Strain Driven Anomalous Anisotropic Enhancement in the Thermoelectric Performance of monolayer MoS$_{2}$. (arXiv:2203.12991v2 [cond-mat.mtrl-sci] UPDATED)
Saumen Chaudhuri, Amrita Bhattacharya, A. K. Das, G. P. Das, B. N. Dev

First principles density functional theory based calculations have been performed to investigate the strain and temperature induced tunability of the thermoelectric properties of monolayer (ML) MoS$_2$. Modifications in the electronic and phononic transport properties, under two anisotropic uniaxial strains along the armchair (AC) and zigzag (ZZ) directions, have been explored in detail. Considering the intrinsic carrier-phonon scattering, we found that the charge carrier mobility ($\mu$) and relaxation time ($\tau$) increase remarkably for strains along the ZZ direction. Concomitantly, strain along the ZZ direction significantly reduces the lattice thermal conductivity ($\kappa_\text{L}$) of ML-MoS$_2$. The combined effect of shortened phonon relaxation time and group velocity, and the reduced Debye temperature is found to be the driving force behind the lowering of $\kappa_\text{L}$. The large reduction in $\kappa_\text{L}$ and increase in $\tau$, associated with the strains along the ZZ direction, act in unison to result in enhanced efficiency and hence, improved thermoelectric performance. Nearly $150\%$ enhancement in the thermoelectric efficiency can be achieved with the optimal doping concentration. We, therefore, highlight the significance of in-plane tensile strains, in general, and strains along the ZZ direction, in particular, in improving the thermoelectric performance of ML-MoS$_2$.

Electron pairing across a band intersection may create a highly conductive state. (arXiv:2207.05974v2 [cond-mat.str-el] UPDATED)
Maxim Trushin, Liangtao Peng, Girish Sharma, Giovanni Vignale, Shaffique Adam

Electrons in metals form a Fermi surface separating occupied from unoccupied states in momentum space at zero temperature. Interactions between electrons are usually accounted for by the Landau theory of Fermi liquids; however, little is known about the stability of the Fermi liquid when the Fermi level intercepts the crossing point between two bands, shrinking the Fermi surface to a set of points known as conical intersections. Here we consider the possibility of pairing electronic states across conical intersections that results in a Bardeen-Cooper-Schrieffer-like state restricted to a finite range of energies around the crossing point, hence, "floating" over an ordinary Fermi sea of occupied states in the lower band. Although this state is not superconducting in the usual sense and does not exhibit a gap in its excitation spectrum, it is nevertheless immune to elastic scattering caused by any kind of disorder, and is therefore expected to exhibit high electric conductivity at low temperature, similar to a real superconductor. The stability of this correlated state requires high density of electronic states in the vicinity of the crossing point -- a feature that may occur in twisted multilayer graphene structures, which are experimentally available. Our findings thus open an exciting opportunity for creating a new class of highly conductive materials.

Imaging the electron charge density in monolayer MoS2 at the {\AA}ngstrom scale. (arXiv:2210.09478v3 [cond-mat.mtrl-sci] UPDATED)
Joel Martis, Sandhya Susarla, Archith Rayabharam, Cong Su, Timothy Paule, Philipp Pelz, Cassandra Huff, Xintong Xu, Hao-Kun Li, Marc Jaikissoon, Victoria Chen, Eric Pop, Krishna Saraswat, Alex Zettl, Narayana R. Aluru, Ramamoorthy Ramesh, Peter Ercius, Arun Majumdar

Four-dimensional scanning transmission electron microscopy (4D-STEM) has recently gained widespread attention for its ability to image atomic electric fields with sub-{\AA}ngstrom spatial resolution. These electric field maps represent the integrated effect of the nucleus, core electrons and valence electrons, and separating their contributions is non-trivial. In this paper, we utilized simultaneously acquired 4D-STEM center of mass (CoM) images and annular dark field (ADF) images to determine the electron charge density in monolayer MoS2. We find that both the core electrons and the valence electrons contribute to the derived electron charge density. However, due to blurring by the probe shape, the valence electron contribution forms a nearly featureless background while most of the spatial modulation comes from the core electrons. Our findings highlight the importance of probe shape in interpreting charge densities derived from 4D STEM.

Phase Separation Driven by Active Flows. (arXiv:2302.00153v2 [cond-mat.soft] UPDATED)
Saraswat Bhattacharyya, Julia M. Yeomans

We extend the continuum theories of active nematohydrodynamics to model a two-fluid mixture with separate velocity fields for each fluid component, coupled through a viscous drag. The model is used to study an active nematic fluid, mixed with an isotropic fluid. We find micro-phase separation, and argue that this results from an interplay between active anchoring and active flows driven by concentration gradients. The results may be relevant to cell-sorting and the formation of lipid rafts in cell membranes.

Conductance asymmetry in proximitized magnetic topological insulator junctions with Majorana modes. (arXiv:2303.16261v2 [cond-mat.mes-hall] UPDATED)
Daniele Di Miceli, Eduárd Zsurka, Julian Legendre, Kristof Moors, Thomas Schmidt, Llorenç Serra

We theoretically discuss electronic transport via Majorana states in magnetic topological insulator-superconductor junctions with an asymmetric split of the applied bias voltage. We study normal-superconductor-normal (NSN) junctions made of narrow (wire-like) or wide (film-like) magnetic topological insulator slabs with a central proximitized superconducting sector. The occurrence of charge non-conserving Andreev processes entails a nonzero conductance related to an electric current flowing to ground from the proximitized sector of the NSN junction. We show that topologically-protected Majorana modes require an antisymmetry of this conductance with respect to the point of equally split bias voltage across the junction.

Fundamental bound on topological gap. (arXiv:2306.00078v2 [cond-mat.mes-hall] UPDATED)
Yugo Onishi, Liang Fu

We provide a universal tight bound on the energy gap of topological insulators by exploring relationships between topology, quantum geometry, and optical absorption. Applications of our theory to infrared absorption near topological band inversion, magnetic circular dichorism in Chern insulators, and topological gap in moir\'e materials are demonstrated.

Reconstruction, rumpling, and Dirac states at the (001) surface of a topological crystalline insulator Pb1-xSnxSe. (arXiv:2306.03582v2 [cond-mat.mtrl-sci] UPDATED)
A. Łusakowski, P. Bogusławski, T. Story

Equilibrium atomic configuration and electronic structure of the (001) surface of IV-VI semiconductors PbTe, PbSe, SnTe and SnSe, is studied using the density functional theory (DFT) methods. At surfaces of all those compounds, the displacements of ions from their perfect lattice sites reveal two features characteristic of the rock salt crystals. First, the ionic displacements occur only along the direction perpendicular to the surface, and they exhibit the rumpling effect, i.e., the vertical shifts of cations and anions differ. Second, the interlayer spacing of the first few monolayers at the surface oscillates. Our results are in good agreement with the previous X-ray experimental data and theoretical results where available. They also are consistent with the presence of two {110} mirror planes at the (001) surface of the rock salt. One the other hand, experiments preformed for the topological Pb$_{1-x}$Sn$_x$ Se alloy indicate breaking of the mirror symmetry due to a large 0.3 {\AA} relative displacement of the cation and anion sublattices at the surface, which induces the opening of the gap of the Dirac cones. Our results for Pb$_{1-x}$Sn$_x$Se including the simulated STM images, are in contradiction with these findings, since surface reconstructions with broken symmetry are never the ground state configurations. The impact of the theoretically determined surface configurations and of the chemical disorder on the surface states is analyzed.

Edge Theories for Anyon Condensation Phase Transitions. (arXiv:2307.12509v2 [cond-mat.str-el] UPDATED)
David M. Long, Andrew C. Doherty

The algebraic tools used to study topological phases of matter are not clearly suited to studying processes in which the bulk energy gap closes, such as phase transitions. We describe an elementary two edge thought experiment which reveals the effect of an anyon condensation phase transition on the robust edge properties of a sample, bypassing a limitation of the algebraic description. In particular, the two edge construction allows some edge degrees of freedom to be tracked through the transition, despite the bulk gap closing. The two edge model demonstrates that bulk anyon condensation induces symmetry breaking in the edge model. Further, the construction recovers the expected result that the number of chiral current carrying modes at the edge cannot change through anyon condensation. We illustrate the construction through detailed analysis of anyon condensation transitions in an achiral phase, the toric code, and in chiral phases, the Kitaev spin liquids.

Raman Spectroscopy of Monolayer to Bulk PtSe2 Exfoliated Crystals. (arXiv:2307.15520v2 [cond-mat.mtrl-sci] UPDATED)
Marin Tharrault, Eva Desgué, Dominique Carisetti, Bernard Plaçais, Christophe Voisin, Pierre Legagneux, Emmanuel Baudin

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 cristalline 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.

Found 2 papers in prb
Date of feed: Wed, 02 Aug 2023 03:17:01 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]+)

Condensation of elastic pseudogauge fields and quantized response in the condensates
Andreas Sinner and Zeinab Rashidian
Author(s): Andreas Sinner and Zeinab Rashidian

The parallels between the models of the weakly interacting Bose gas and elastic pseudogauge fields coupled to the massive Dirac fermions in two spatial dimensions reveal an intricate property of the Berry term in the former as compared to the Chern-Simons term of the latter. Guided by the Bogoliubov…

[Phys. Rev. B 108, 054501] Published Tue Aug 01, 2023

Magnetic states of graphene proximitized Kitaev materials
Jingtian Shi and A. H. MacDonald
Author(s): Jingtian Shi and A. H. MacDonald

Single-layer $α$-ruthenium trichloride $(α\text{−}{\mathrm{RuCl}}_{3})$ has been proposed as a potential quantum spin liquid. Graphene/${\mathrm{RuCl}}_{3}$ heterobilayers have been extensively studied with a focus on the large interlayer electron transfer that dopes both materials. Here we examine …

[Phys. Rev. B 108, 064401] Published Tue Aug 01, 2023

Found 6 papers in prl
Date of feed: Wed, 02 Aug 2023 03:17:02 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]+)

Color-Dual Fates of ${F}^{3}$, ${R}^{3}$, and $\mathcal{N}=4$ Supergravity
John Joseph M. Carrasco, Matthew Lewandowski, and Nicolas H. Pavao
Author(s): John Joseph M. Carrasco, Matthew Lewandowski, and Nicolas H. Pavao

We find that the duality between color and kinematics can be used to inform the high energy behavior of effective field theories. Namely, we demonstrate that the massless gauge theory of Yang-Mills deformed by a higher-derivative ${F}^{3}$ operator cannot be tree level color dual while consistently …

[Phys. Rev. Lett. 131, 051601] Published Tue Aug 01, 2023

Neutrino-Induced Coherent ${π}^{+}$ Production in C, CH, Fe, and Pb at $⟨{E}_{ν}⟩∼6\text{ }\text{ }\mathrm{GeV}$
M. A. Ramírez et al. (The MINERvA Collaboration)
Author(s): M. A. Ramírez et al. (The MINERvA Collaboration)

MINERvA has measured the ${ν}_{μ}$-induced coherent ${π}^{+}$ cross section simultaneously in hydrocarbon (CH), graphite (C), iron (Fe), and lead (Pb) targets using neutrinos from 2 to 20 GeV. The measurements exceed the predictions of the Rein-Sehgal and Berger-Sehgal PCAC based models at multi-GeV…

[Phys. Rev. Lett. 131, 051801] Published Tue Aug 01, 2023

Absence of Topological Protection of the Interface States in ${\mathbb{Z}}_{2}$ Photonic Crystals
Shupeng Xu, Yuhui Wang, and Ritesh Agarwal
Author(s): Shupeng Xu, Yuhui Wang, and Ritesh Agarwal

Inspired from electronic systems, topological photonics aims to engineer new optical devices with robust properties. In many cases, the ideas from topological phases protected by internal symmetries in fermionic systems are extended to those protected by crystalline symmetries. One such popular phot…

[Phys. Rev. Lett. 131, 053802] Published Tue Aug 01, 2023

Topological Superconductivity in Doped Magnetic Moiré Semiconductors
Valentin Crépel, Daniele Guerci, Jennifer Cano, J. H. Pixley, and Andrew Millis
Author(s): Valentin Crépel, Daniele Guerci, Jennifer Cano, J. H. Pixley, and Andrew Millis

Robust attraction and low-energy symmetry properties in transition metal dichalcogenide twisted bilayers may produce topologically protected superconductivity.

[Phys. Rev. Lett. 131, 056001] Published Tue Aug 01, 2023

Anisotropic Topological Anderson Transitions in Chiral Symmetry Classes
Zhenyu Xiao, Kohei Kawabata, Xunlong Luo, Tomi Ohtsuki, and Ryuichi Shindou
Author(s): Zhenyu Xiao, Kohei Kawabata, Xunlong Luo, Tomi Ohtsuki, and Ryuichi Shindou

We study quantum phase transitions of three-dimensional disordered systems in the chiral classes (AIII and BDI) with and without weak topological indices. We show that the systems with a nontrivial weak topological index universally exhibit an emergent thermodynamic phase where wave functions are de…

[Phys. Rev. Lett. 131, 056301] Published Tue Aug 01, 2023

Highly Anisotropic Even-Denominator Fractional Quantum Hall State in an Orbitally Coupled Half-Filled Landau Level
Chengyu Wang, A. Gupta, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, R. Winkler, and M. Shayegan
Author(s): Chengyu Wang, A. Gupta, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, R. Winkler, and M. Shayegan

The even-denominator fractional quantum Hall states (FQHSs) in half-filled Landau levels are generally believed to host non-Abelian quasiparticles and be of potential use in topological quantum computing. Of particular interest is the competition and interplay between the even-denominator FQHSs and …

[Phys. Rev. Lett. 131, 056302] Published Tue Aug 01, 2023

Found 1 papers in sci-rep

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]+)

Author Correction: Flotillin-2 promotes metastasis of nasopharyngeal carcinoma by activating NF-κB and PI3K/Akt3 signaling pathways
Yuxiang Chen

Scientific Reports, Published online: 01 August 2023; doi:10.1038/s41598-023-39544-1

Author Correction: Flotillin-2 promotes metastasis of nasopharyngeal carcinoma by activating NF-κB and PI3K/Akt3 signaling pathways