Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session S42: Electronic and Transport Properties of Transition Metal DichalcogenidesLive
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: Mehmet Dogan, University of California, Berkeley |
Thursday, March 18, 2021 11:30AM - 11:42AM Live |
S42.00001: Anisotropic dispersion of dielectric permittivity of few-layer ReS2 Devarshi Chakrabarty, Avijit Dhara, Pritam Das, Aswini Kumar Pattanayak, Shreya Paul, Shreyashi Mukherjee, Sajal Dhara Rhenium disulphide (ReS2) from the family of Group VII transition metal dichalcogenides (TMDs) displays unique in-plane anisotropic optical and electronic properties due to its distorted 1T’ crystal structure. Here, we present polarisation-resolved reflectance measurements performed on few-layer ReS2 exfoliated on SiO2/Si substrate. Using the transfer matrix method, we model and obtain the polarisation-dependent complex dielectric function of ReS2 from these measurements. We observe dispersion of the principal axes in the observed wavelength range. This is due to its triclinic symmetry, as well the presence of anisotropic excitonic resonances in ReS2 conferring a wavelength dependence to all components of its dielectric tensor. This paves the way to designing polarisation sensitive photonic devices using ReS2, and can potentially be used to explore conveniently tuneable light-matter coupling in photonic devices. |
Thursday, March 18, 2021 11:42AM - 11:54AM Live |
S42.00002: Spin-valley locked instabilities in moire transition metal dichalcogenides with conventional and higher-order Van Hove singularities Yi-Ting Hsu, Fengcheng Wu Recent experiments have observed correlated insulators and possible superconductivity in twisted bilayer transition metal dichalcogenides (TMDs). Besides the spin-valley locked bands due to Ising spin-orbit coupling, homo-bilayer moire TMDs also possess either logarithmic or power-law divergent Van Hove singularities (VHS) near the Fermi surface, controllable by an external displacement field. Here, we perform a perturbative RG analysis to study the dominant instabilities in homo-bilayer TMDs for both the conventional and higher-order VHS cases. We find that the spin-valley locking largely alters the RG flows and leads to instabilities unexpected in graphene-based moire systems, such as spin- and valley-polarized phase, spin-valley density waves, and topological superconductivity with mixed parity. In particular, for the case with two higher-order VHS, we find a metallic state with no symmetry breaking despite the diverging bare susceptibility. This “super-metal-like” state arises from the constraints imposed by the spin-valley locking. Our results show how spin-valley locking significantly affects the RG analysis and demonstrate that moire TMDs are ideal platforms to realize various exotic spin-valley locked phases. |
Thursday, March 18, 2021 11:54AM - 12:06PM Live |
S42.00003: Insights into negative differential resistance in MoS2 Esaki diodes: A first-principles perspective Adam Bruce, Shuanglong Liu, James Nathan Fry, H-P. Cheng MoS2 is a two-dimensional transition metal dichalcogenide with band gap programable in number of layers and external electric field. Experimentation has shown the existence of band to band tunneling both in plane and between layers (interlayer band to band tunneling). We present our findings, using density functional theory with non-equilibrium Green’s functions (DFT + NEGF), on the relation between band alignment and transmission in both planar and side-stack MoS2 p-i-n junction configurations. Additionally, we connect these results with the IV character of our junctions to demonstrate the Esaki diode behavior of these junctions. |
Thursday, March 18, 2021 12:06PM - 12:18PM Live |
S42.00004: Insulating States in WSe2 Twisted From 60 Degrees Jordan Pack, Qianhui Shi, Song Liu, Kenji Watanabe, Takashi Taniguchi, James Hone, Cory R Dean Twisted bilayers of van der Waals materials have proven to be a fascinating platform for studying correlated electron behavior since the long wavelength moiré pattern induces flat bands in the system. In transition metal dichalcogenides homobilayers, there are two distinct stackings with long wavelength moiré patterns: one starting from a 0° and another from a 60° twist angle. Due to the locked spin and valley degrees of freedom in WSe2, this second stacking should suppress interlayer tunneling which, in the presence of flat bands, could allow for the formation of states with novel interlayer correlations. We will present electronic transport and compressibility measurements of the correlated insulating states in these heterostructures. |
Thursday, March 18, 2021 12:18PM - 12:30PM Live |
S42.00005: Area, temperature, velocity, and edge effects in the sliding of structurally lubric 2D materials Jin Wang, Ali Khosravi, Andrea Vanossi, Erio Tosatti Graphene and many other two-dimensional (2D) materials entered the scene in the last two decades. Their strong and yet membrane-like sheets permit – actually require -- deposition, giving rise to interfaces whose tribological properties under shear stress must be understood and controlled. We carried out selected simulation case studies with variously twisted, structurally incommensurate interfaces involving graphene. There is first of all a basic difference between "small" and "large" twist angles -- only the latter are superubric and free sliding in the usual sense. The kinetic friction of a superlubrically sliding island is linear with velocity ("viscous") at large velocity or large temperature -- regimes where, dominated by the island's body, friction grows proportional to area. At low velocities and low temperatures, conversely, kinetic friction is, like static friction, dominated by the island's edges. Therefore it grows at most as the perimeter, and with a much weaker velocity dependence, as expected for stick-slip friction. Recovering and extending many results already present in literature, the overall picture obtained applies to general 2D interfaces, including current and future bilayer and multilayer systems. |
Thursday, March 18, 2021 12:30PM - 12:42PM Live |
S42.00006: Measurement of Conduction and Valence Bands g-factors in a Transition Metal Dichalcogenide Monolayer Lei Ren, Cedric ROBERT, Hanan Dery, Dinh Van Tuan, Emmanuel Courtade, Min Yang, Bernhard Urbaszek, Delphine Lagarde, Kenji Watanabe, Takashi Taniguchi, Thierry Amand, Xavier Marie The electron valley and spin degree of freedom in monolayer transition metal dichalcogenides can be manipulated in optical and transport measurements performed in magnetic fields. The key parameter for determining the Zeeman splitting, namely the separate contribution of the electron and hole g-factor, is inaccessible in most measurements. Here we present an original method that gives access to the respective contribution of the conduction and valence band to the measured Zeeman splitting. It exploits the optical selection rules of exciton complexes, in particular the ones involving inter-valley phonons, avoiding strong renormalization effects that compromise single particle g-factor determination in transport. These studies yield a direct determination of single band g factors. We measure gc1= 3.84±0.1, gc2=0.86±0.1 for the top (bottom) conduction band and gv=6.1±0.1 for the valence band of monolayer WSe2. These measurements are helpful for more quantitative interpretation of optical and transport measurements performed in magnetic fields. The measured g-factor values are also valuable input parameters for optimizing band structure calculations of these 2D materials. |
Thursday, March 18, 2021 12:42PM - 12:54PM Live |
S42.00007: A unique pentagonal network structure of the NiS2 monolayer with high stability and a tunable bandgap Chang-Tian Wang, Shixuan Du Two dimensional atomic crystals with pentagonal building blocks have attracted extensive interest in recent years. Here, with the help of ab initio calculations based on density functional theory, we report a unique pentagonal structured NiS2 monolayer in P-421m symmetry, named P-NiS2. Its dynamic stability has been confirmed by phonon mode analysis. Molecular dynamics simulations and total-energy calculations show that this new P-NiS2 has robust thermal stability and energetically more stable than all other reported NiS2 monolayer structures. Electronic band structure calculations show that it is a semiconductor with an indirect band gap of 1.94 eV. Furthermore, we find that small strain triggers a transition from the indirect to direct band gap for this P-NiS2, suggesting its great potential for applications based on strain-engineering techniques. |
Thursday, March 18, 2021 12:54PM - 1:06PM Live |
S42.00008: Studying Strain Dependence of Electronic and Structural Phases in Tantalum Disulfide Susana Torres-Londono, Shannon Haley, Meera Aravinth, Sophie Weber, James Analytis, Sinead Griffin Tantalum Disulfide (TaS2) belongs to the family of transition metal dichalcogenides studied for its potential in nanoelectronics, photonics, and energy storage. TaS2 exists in several phases with differing functional electronic properties whose stability can be tuned with strain, pressure, and synthesis conditions. In this talk, I will discuss the structural and electronic phase diagram of 1T and 2H phases of TaS2 with the application of pressure and strain using Density Functional Theory. I will discuss how strain can be used to tune both the structural and electronic phases, focusing on how changes in the Fermi surface topology can influence the formation of charge density waves. Finally, I will speak to how our theoretical predictions connect to experimental transport measurements of 1T and 2H phases at various applied strains, using it to map changes in the electronic properties and the Fermi surface of the material. |
Thursday, March 18, 2021 1:06PM - 1:18PM Not Participating |
S42.00009: Charge Density Wave Proximity Effect in Graphene on 1T-TaS2 Michael Altvater, Sheng-Hsiung Hung, Nikhil Tilak, Choong-Jae Won, Guohong Li, Sang-Wook Cheong, Chung-Hou Chung, Horng-Tay Jeng, Eva Andrei Due to the non-local nature of electrons in materials, ordered states within a correlated material cannot abruptly change to another type of ordering at the interface with another material. As a result, correlated electron states persist into the normal metal (and vice versa). Several well-known examples of contact proximity effects have led to observations of magnetism, spin-orbit effects, and superconductivity induced in normal metals by contact with a correlated material. Here, we provide microscopic evidence, by means of scanning tunneling microscopy/spectroscopy and modelling based on density functional theory, of a novel proximity induced charge density wave in graphene placed on 1T-TaS2. |
Thursday, March 18, 2021 1:18PM - 1:30PM Live |
S42.00010: Anisotropic Phonon Modes and Thermal conductivities of the quasi-1D materials TaSe3 and ZrTe3 Topojit Debnath, Bishwajit Debnath, Roger Lake The metallic quasi-1D materials TaSe3 and ZrTe3 were demonstrated to have high current carrying capacity and resilience to scaling. These crystals consist of van der Waals planes of strongly bonded one-dimensional chains more weakly bonded to neighboring chains. To understand their thermal transport properties, we determined their phonon spectra and thermal conductivities using density functional theory and the phonon Boltzmann transport equation. The anisotropy of both the LA phonon velocities and thermal conductivities is larger in TaSe3 than in ZrTe3. The maximum LA phonon velocity in ZrTe3 occurs in the cross-chain direction, which is a result of the strong cross-chain bonding. The maximum thermal conductivities for both materials occur in the chain directions. A significant percentage of the heat is carried by optical phonons. The phonon lifetimes and mean free paths for the low frequency modes is much shorter in TaSe3 than in ZrTe3 due to the presence of low-frequency optical modes and zone-folding features in TaSe3. Thermal conductivities are calculated for different crystallographic directions over a range of temperatures [arXiv:2010.08165]. |
Thursday, March 18, 2021 1:30PM - 1:42PM Live |
S42.00011: Unveiling the metallic phases of twisted transition metal dichalcogenides Augusto Ghiotto, En-Min Shih, Giancarlo S. S. Pereira, Lei Wang, Lede Xian, Daniel Rhodes, Cheng Tan, Dante Kennes, Martin Claassen, Yusong Bai, Bumho Kim, Kenji Watanabe, Takashi Taniguchi, Xiaoyang Zhu, James Hone, Angel Rubio, Cory Dean, Abhay Narayan Emergent quantum phases driven by electronic interactions can manifest in materials with narrowly dispersing, i.e. “flat", energy bands. One such system is twisted bilayer tungsten diselenide (tWSe2), a semiconducting transition metal dichalcogenide (TMD). Unlike twisted bilayer graphene where the flat band appears only within a narrow range around a “magic angle", we have observed correlated insulating states over a continuum of angles, spanning 4° to 5.1°. Metal-insulator transitions can be driven in this system both by doping as well as by vertical electric field. We find that immediately adjacent to the metal-insulator transition lies a region of T-linear resistivity that extends down to the lowest temperature of our measurement (200 mK). Further away from the metal-insulator boundary, the low temperature resistance recovers a Fermi-liquid quadratic dependence on temperature. This T-linear resistivity becomes sub-linear at temperatures of 30-60 K, and eventually gives rise to a temperature-independent saturated resistance at high temperature. Magnetoresistance measurements at low magnetic fields show a B-linear dependence, with a slope that is maximized where the T-linear behavior is observed in the phase diagram. |
Thursday, March 18, 2021 1:42PM - 1:54PM Live |
S42.00012: Unraveling chemical bonding and Born charge in 1T-HfS2 Sabine Neal, Shutong Li, Turan Birol, Janice Musfeldt We combine infrared absorption and Raman scattering spectroscopies to explore the properties of 1T-HfS2- a heavy transition metal chalcogenide with strong spin-orbit coupling due to incorporation of the 5d center. We employ the LO-TO splitting of the Eu mode along with a reevaluation of mode mass, unit cell volume, and dielectric constant to reveal the Born effective charge. We find ZB*= 5.33e, in excellent agreement with complementary first principles calculations. In addition to resolving controversy over the nature of chemical bonding in this system, we decompose the Born charge into polarizability and local (ionic) charge. We find α= 5.07 Å3 and Z*= 5.19e, respectively. In order to understand how ZB* relates to the nominal 4+ charge of the Hf center, we decompose the theoretical Born effective charge into band-by-band contributions, and find that polar displacement-induced charge transfer from sulfur p to hafnium d orbitals is responsible for the enhancement of Born charge. 1T-HfS2 is thus an ionic crystal with strong and dynamic covalent effects. Taken together, our work places the vibrational properties of 1T-HfS2 on a firm foundation and opens the door to intercalation and doping studies, growth of nanotubes, and sheet exfoliation. |
Thursday, March 18, 2021 1:54PM - 2:06PM Live |
S42.00013: Metallicity of 2H-MoS2 Induced by Au Hybridization Masa Ishigami, Stephanie Lough, Darian Smalley, Talat Rahman, Duy Le, Brandon T Blue
|
Thursday, March 18, 2021 2:06PM - 2:18PM Live |
S42.00014: Quantitative measurement of layer-to-layer electronic coupling in bilayer MoS2 Wei-Ting Hsu, Jiamin Quan, Peng-Jen Chen, Wen-Hao Chang, Xiaoqin (Elaine) Li, Jung-Fu Lin, Chih-Kang Shih Interlayer electronic coupling plays a critical role in determining the electronic properties of van der Waal (vdW) bilayers. In particular, the coupling strength is dictated by the stacking configuration and the interlayer spacing. While the former has been well established, the influence of interlayer spacing still remains largely unexplored. Here, by measuring the optical transition of bilayer MoS2 in the diamond anvil cell, we quantitatively determined the interlayer coupling at various critical points of the Brillouin zone. The K-point coupling strength we obtained is ~40 meV, which can be increased to more than 100 meV at a reduced interlayer spacing of ~8%. In addition, the energy evolution of the indirect gap is used to measure the coupling strength of Q and Γ points. All experimental results are compared with the density functional theory. Our work has confirmed the great potential in tailoring vdW bilayers using compressive pressure. |
Thursday, March 18, 2021 2:18PM - 2:30PM Live |
S42.00015: Interlayer coupling induced two-dimensional electron lattice in transition metal dichalcogenides thin-films Priyanka Manchanda, Ivan Naumov, Pratibha Dev The strong interlayer coupling between vertically stacked two-dimensional layered materials dramatically affect the electronic structure and lattice vibration of the materials and give rise to many unique phenomena such as new interlayer excitons, and unconventional superconductivity. Using density functional theory-based calculations, we show that the interlayer interaction between the transition metal dichalcogenides layers also gives rise to an electronic lattice, which is formed between the layers. The charge in this Kagome-like electronic lattice depends on the strength of interlayer interaction. It may give rise to many interesting phenomena including topologically non-trivial states. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700