Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session GG10: V: 2D-Electronic PropertiesFocus
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Sponsoring Units: DMP Chair: Salvador Barraza-Lopez, University of Arkansas Room: Virtual Room 10 |
Monday, March 20, 2023 12:30PM - 1:06PM |
GG10.00001: Visualizing fractional excitations in a Tomonaga-Luttinger liquid Invited Speaker: Wei Ruan Tomonaga-Luttinger liquids (TLLs) have been predicted to host fractional excitations, which are emergent exotic particles that separate the spin and the charge of electrons. This phenomenon is commonly referred to as the spin-charge separation, which is a key to understanding electron correlation effects. Much work on TLLs has focused on collective response of the fractional excitations, but direct imaging or local spectroscopy of them is quite challenging due to their fractional nature. |
Monday, March 20, 2023 1:06PM - 1:18PM |
GG10.00002: Large valley (orbital) polarization near a magnetic impurity in monolayer NbSe2: Green's Function and density-functional studies Tapesh Gautam, Sashi S Satpathy, Birabar R Nanda, Amit Chauhan, Mayank Gupta We show that a magnetic impurity in the monolayer transition metal dichalcogenides (TMDs) such as 2H-NbSe2 induces a valley (orbital) polarization in its vicinity in addition to the standard spin polarization of the electron gas due to the coupled spin-valley physics. There is a site-dependent occupancy difference between the angular momentum orbitals, L+ - L-, where L± ≡ ¦x2- y2 >± i ¦xy >, which is large close to the impurity site, but diminishes away from it, similar to the Friedel oscillation. The spin/orbital polarization is studied from the impurity Green's function method using the low-energy k.p Hamiltonian (valley orbital model) as well as from density-functional calculations. Such magnetic-impurity-induced orbital polarization should exist to a varying degree in any crystal with spin-orbit coupling, but is especially large in non-centrosymmetric crystals such as the monolayer TMDs. To our knowledge, this is the first time that an orbital polarization has been predicted near an impurity in any system. Our results should be readily accessible for experimental study using conventional and spin polarized scanning tunneling microscopy as well as optical experiments with polarized light. |
Monday, March 20, 2023 1:18PM - 1:30PM |
GG10.00003: Enhanced superconductivity through virtual tunneling in Bernal bilayer graphene coupled to WSe$_2$ Yang-Zhi Chou, Fengcheng Wu Motivated by a recent experiment [arXiv:2205.05087], we investigate a possible mechanism that enhances superconductivity in hole-doped Bernal bilayer graphene due to a proximate WSe$_2$ monolayer. We show that the virtual tunneling between WSe$_2$ and Bernal bilayer graphene, which is known to induce Ising spin-orbit coupling, can generate an additional attraction between two holes, providing a potential explanation for enhancing superconductivity in Bernal bilayer graphene. Using the microscopic interlayer tunneling, we derive the Ising spin-orbit coupling and the effective attraction as functions of the twist angle between Bernal bilayer graphene and WSe$_2$ monolayer. Our theory provides an intuitive and physical explanation for the intertwined relation between Ising spin-orbit coupling and superconductivity enhancement, which should motivate future studies. |
Monday, March 20, 2023 1:30PM - 1:42PM |
GG10.00004: Symmetry-enforced nodal lines in the band structures of vacancy-engineered graphene Matheus S Martins de Sousa, Wei Chen, Mariana Malard Sales Andrade, Fanyao Qu, Fujun Liu We elaborate that single-layer graphene with periodic vacancies can have a band structure containing nodal lines or nodal loops, opening the possibility of graphene-based electronic or spintronic devices with novel functionalities. The principle is that by removing carbon atoms such that the lattice becomes nonsymmorphic, every two sublattices in the unit cell will map to each other under glide plane operation. This mapping yields degenerate eigenvalues for the glide plane operation, which guarantees that the energy bands must stick together pairwise at a boundary of the Brillouin zone. Moving away from the Brillouin zone boundary causes the symmetry-enforced nodal lines to split, resulting in accidental nodal lines caused by the crossings of the split bands. Moreover, the density of states at the Fermi level may be dramatically enhanced if the nodal lines cross the Fermi level. The nodal lines occur in a variety of vacancy configurations even in the presence of Rashba spin-orbit coupling. Finally, our theory also explains the nodal loops surrounding the entire Brillouin zone of chevron-type nanoporous graphene fabricated in a recent experiment. |
Monday, March 20, 2023 1:42PM - 1:54PM |
GG10.00005: Vertical Heterostructure of 2D Polar Binary Compounds(GeC/SiGe): First- Principles study Safia A Alharbi, Ahmad Nagab Alharbi, Ming Yu It is well known that vdW interaction plays a major role between adjacent layers in 2D vertical heterostructures. However, our preliminary study shows that the in-plane charge transfer between elements in 2D polar materials, such as SiGe or GeC monolayer, opens our mind to understand the effect of the electrostatic force triggered by such in-plane charge transfer when design vertical heterostructure build by polar monolayers. Our systematic analysis pointed out that, in addition to the vdW weak interaction, there is an electrostatic interlayer bonding formed by the orbital hybridization in the interlayer region which has a strong effect on the structural and electronic properties of such vertical polar heterostructures and shows the ability to modify them by the different staking constituent’s arrangement. More interestingly, we found a built-in electric field in the interlayer region build by the charge redistribution, which may affect the probability of photo-generated carrier recombination. These promising results make such polar heterostructures a bright candidate in the application of nanoelectronics. |
Monday, March 20, 2023 1:54PM - 2:06PM |
GG10.00006: Mixed-dimensional graphene/SnxPb1-xTe heterostructures: electronic structure properties from first principles Ivan I Naumov, Pratibha Dev, Sharmila Shirodkar, Gregory Stephen, Nicholas A Blumenschein, Jennifer E DeMell, Adam L Friedman Moiré superstructures involving mixed-dimensional (2D and 3D) materials are expected to result in novel electronic properties that are potentially just as interesting as those found by moiré engineering of interfaces between 2D layered materials. In this context, the interface between graphene and SnTe is especially interesting since both the materials separately exhibit remarkable properties, such as the Dirac cones of graphene and topological electronic surface states of SnTe. As shown recently, a graphene/SnxPb1-xTe (111) heterostructure exhibits carrier mobilities and magnetoresistance greater than either material alone [1]. To understand the physics behind these experiments, we have studied the electronic properties of the graphene/SnxPb1-xTe heterostructure, in which a graphene monolayer is in van der Waals contact with a Te-terminated surface of lead-doped SnTe. We found that adding enough lead, destroys the SnTe topological surface states. However, since the (111) surface is polar, alternate metallic surface states are created in SnPbTe due to partial filling of the surface states. Our ab initio calculations show that these surface states, under graphene, are not confined to very top layer but extend into the bulk region over approximately 10 layers. This 2D electron gas created in the system under discussion is similar to that found at the LaAlO3/SrTiO3 interface, and can explain the experimental observations of Ref. [1]. |
Monday, March 20, 2023 2:06PM - 2:18PM |
GG10.00007: A proposal for optical control of topological memory in Chern insulators realized in moiré multilayers Victor M Yakovenko, Sergey S Pershoguba Under suitable experimental conditions, some twisted graphene multilayers and transition-metal dichalcogenides become Chern insulators. They exhibit the anomalous quantum Hall effect and orbital magnetization due to spontaneous valley polarization. We study (theoretically) the interaction of a Chern insulator with circularly polarized light derived from the optical Stark energy shift. The interaction energy contains an antisymmetric term that couples the helicity of incident light and the Berry curvature of the electronic system. Taking advantage of this interaction, we propose optical switching of the sign of the Chern number, representing topological memory, by circularly polarized light. Moreover, two laser beams of opposite circular polarization can nucleate domains of opposite magnetization and thus produce an optically-configurable domain wall carrying topologically protected chiral edge modes. |
Monday, March 20, 2023 2:18PM - 2:30PM |
GG10.00008: Electrical characterization of Graphene Oxide films in Field Effect Transistor configuration Narly A Echeverry Montoya, J. J. Prias-Barragan, Carlos Perdomo Vela Electrical characterization of pyrolytic Graphene Oxide (GO) films (5.3% of oxidation), in configuration of field effect transistor (FET), is presented here. GO-FET´s were electrically characterized by the current-voltage method, varying temperature of 20 to 300 K; finding, a behavior of voltage-controlled current source and a high electrical mobility value of 1.2 x10 4 cm 2 /Vs at 300 K, as expected. Results revealed that decreases temperature, increases the electrical resistance and this behavior was described employing the 3D-VRH model. These results suggest that GO-FET is an attractive device to high-frequency commutation. |
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