Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session C18: Graphene and van der Waals Materials II |
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Sponsoring Units: DCMP DMP Chair: Sufei Shi, Rensselaer Polytech Institute Room: LACC 306B |
Monday, March 5, 2018 2:30PM - 2:42PM |
C18.00001: The anisotropic interlayer interaction at MoS2/black phosphorous interface Ziling Li, Ruoyu Yin, Yu Ye The isolation of two-dimensional (2D) layered materials has inspired tremendous efforts across the globe to integrated distinct 2D materials into van der Waals (vdW) heterostructures[1]. Engineering the physical properties of layered materials through vdW interlayer interaction gives a rise to a variety of fascinating physical behaviors or enhances device performances that are not possible to realize with singular 2D materials[2]. At the interface of isotropic MoS2 and anisotropic black phosphorous (BP), we discovered the anisotropic interlayer interaction via polarized Raman spectroscopy. The anisotropic interlayer interaction enables the isotropic MoS2 exhibiting anisotropic Raman signals, in accordance with angle-dependent Raman spectra of anisotropic BP. The anisotropic interlayer interaction might provide a new route to realize MoS2-based angle dependent photonic, electronic and thermoelectric devices. |
Monday, March 5, 2018 2:42PM - 2:54PM |
C18.00002: Electronic properties of armchair MoS2 nanoribbons deposited with nanowires Chi-Hsuan Lee, Chih-Kai Yang Electronic properties of armchair MoS2 nanoribbons with deposited nanowires are investigated using density-functional calculations. The pure armchair MoS2 ribbon with 15 dimer lines has an energy gap around 0.5 eV and zero magnetic moment at the ribbon edge. The nanowire stacked on the ribbon modulates the energy bands near the Fermi level and induces different magnetic properties. Various stacking locations of the nanowires are also considered. The results may be useful for application in nanoelectronic devices. |
Monday, March 5, 2018 2:54PM - 3:06PM |
C18.00003: Electrical spin injection/detection in Cobalt/MoS2 hybrid systems. Shiheng Liang, yuan lu, Huaiwen Yang, bingshan tao, Piotr Laczkowski, stefan Mc-Murty, Gang Wang, Jean-Marie George, Thierry Amand, Sebastien Petit-Watelot, Abdelhak Djeffal, Daniel Lacour, françois montaigne, Michel Hehn, Stephane Mangin, Xavier Marie, Henri Jaffres, Pierre Renucci We demonstrate for the first time the electrical spin injection and detection in a multilayer MoS2 semiconducting channel [1]. A Magnetoresistance around 1 percent has been observed at low temperature through a 450 nm long, 6 monolayer thick channel with a Co/MgO spin injector and detector. it is found that keeping a good balance between the interface resistance and channel resistance is mandatory for the observation of the two-terminal magnetoresistance. The electron spin-relaxation is found to be greatly suppressed in the multilayer MoS2 channel with an in-plane spin polarization. Moreover, for in-plane injection, the electron spin relaxation is found to be greatly damped in a multilayer MoS2 channel. Long spin diffusion length (≈235 nm) and large spin lifetime (≈46 ns) estimated from the measurements make these multilayer systems promising for spintronic applications. S.H. Liang et al., Nature Com. 8, 14947 (2017). |
Monday, March 5, 2018 3:06PM - 3:18PM |
C18.00004: Spin polarized edge states in proximitized ferromagnetic transition metal dichalcogenides Natalia Cortés, Oscar Avalos Ovando, Luis Rosales, Pedro Orellana, Sergio Ulloa Transition metal dichalcogenide (TMD) monolayers deposited on a ferromagnetic substrate such as europium oxide (EuO) experience proximity-induced ferromagnetism. We explore the nature of states appearing at the edge of proximitized TMD ribbons and nanoflakes by means of a real-space three-orbital tight-binding model that incorporates the magnetic interaction effects induced by the substrate. For commensurate structures, such as MoTe2 on EuO, we study spin and orbital composition of states for zigzag and armchair edges. We find that states at zigzag borders are extended and strongly spin-polarized, exhibiting the competition of exchange and spin-orbit coupling. The real-space approach also allows the description of incommensurate systems, such as MoS2 on EuO. The competition of magnetic and lattice periodicities has strong effects on the states, especially on their dispersion and spin texture. |
Monday, March 5, 2018 3:18PM - 3:30PM |
C18.00005: Room temperature charge density wave in vanadium ditelluride (VTe2) Dongyeun Won, Suyeon Cho, Heejun Yang Layered transition metal chalcogenides (TMDs) have been extensively studied in terms of spontaneous lattice distortion such as charge density wave (CDW). In the layered crystals, new order parameters such as flake thickness, defect density and carrier density have been newly used to trigger CDW phase transition. While device applications require room temperature manipulation of the CDW, switching CDW in TMDs at room temperature remains a challenge. We report vanadium ditelluride (VTe2) synthesized by flux method, which shows CDW transition at T=420 K. Since the transition temperature is above the temperature, a distorted lattice structure (monoclinic and C2/m) was observed in our VTe2 at room temperature. Above the T=420 K, the lattice structure changes to a trigonal structure having a higher symmetry. We verified the CDW state by electrical transport measurement, powder and single crystal X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The single-crystalline VTe2 exhibits metallic transport characteristics at room temperature which is unique compared to other group 5 TMDs. |
Monday, March 5, 2018 3:30PM - 3:42PM |
C18.00006: Linear chain model for the low-frequency phonon modes in van der Waals layered materials Jia-An Yan, Lucas Webster One-dimensional linear atomic chain model is applied to understand the atomic vibrations in the low-frequency modes in van der Waals layered materials. We present a systematic study of different methods (analytical, numerical, and electrical circuit analogy) to calculate the atomic vibrational modes and their frequencies, and discuss the effects of different boundary conditions on the results. We also show that for a finite atomic chain with N atoms, the vibrational modes are standing waves, and their vibrational frequencies can be obtained through zone folding of an infinite atomic chain. Finally, the one-atom chain model is extended to a two-atom chain model to study the low-frequency modes in InSe multilayers. |
Monday, March 5, 2018 3:42PM - 3:54PM |
C18.00007: Substrate Doping Effect and Unusually Large Angle van Hove Singularity Evolution in Twisted Bi- and Multilayer Graphene Han Peng, Niels Schroeter, Jianbo Yin, Hailin Peng, Yulin Chen Graphene has demonstrated great potential in new-generation electronic applications due to its unique electronic properties such as large carrier Fermi velocity, ultrahigh carrier mobility, and high material stability. Interestingly, the electronic structures can be further engineered in multilayer graphene by the introduction of a twist angle between different layers to create van Hove singularities (vHSs) at adjustable binding energy. In this work, using angle-resolved photoemission spectroscopy with sub-micrometer spatial resolution, the band structures and their evolution are systematically studied with twist angle in bilayer and trilayer graphene sheets. A doping effect is directly observed in graphene multilayer system as well as vHSs in bilayer graphene over a wide range of twist angles (from 5° to 31°) with wide tunable energy range over 2 eV. In addition, the formation of multiple vHSs (at different binding energies) is also observed in trilayer graphene. |
Monday, March 5, 2018 3:54PM - 4:06PM |
C18.00008: Collimated Ballistic Quasiparticle Transport in a Graphene/hBN Superlattice Aaron Sharpe, Arthur Barnard, John Wallbank, Kenji Watanabe, Takashi Taniguchi, David Goldhaber-Gordon Moiré patterns in van der Waals heterostructures of graphene and other hexagonal crystals such as boron nitride (hBN) are a readily realizable class of 2D superlattices with electronic properties distinct from those of the parent materials. Transport measurements of highly aligned graphene/hBN superlattices showed a band structure with miniband edges, van Hove singularities, and non-circular cyclotron orbits [M. Lee et al, Science 353, 6307 (2016)]. However, several interesting regimes are obscured by the coexistence of multiple bands in different parts of k-space. |
Monday, March 5, 2018 4:06PM - 4:18PM |
C18.00009: On-Demand Spin-Orbit Interaction from Which-Layer Tunability in Bilayer Graphene Jun Khoo, Alberto Morpurgo, Leonid Levitov Spin−orbit interaction (SOI) that is gate-tunable over a broad range is essential to exploiting novel spin phenomena. Achieving this regime has remained elusive because of the weakness of the underlying relativistic coupling and lack of its tunability in solids. Here we outline a general strategy that enables exceptionally high tunability of SOI through creating a which-layer spin−orbit field inhomogeneity in graphene multilayers. An external transverse electric field is applied to shift carriers between the layers with strong and weak SOI. Because graphene layers are separated by subnanometer scales, exceptionally high tunability of SOI can be achieved through a minute carrier displacement. A detailed analysis of the experimentally relevant case of bilayer graphene on a semiconducting transition metal dichalchogenide substrate is presented. In this system, a complete tunability of SOI amounting to its ON/OFF switching can be achieved. New opportunities for spin control are exemplified with electrically driven spin resonance and topological phases with different quantized intrinsic valley Hall conductivities. |
Monday, March 5, 2018 4:18PM - 4:30PM |
C18.00010: Width-tuned magnetic order oscillation on zigzag edges of honeycomb nanoribbons Yuan Zhou, Wen-Chao Chen, ShunLi Yu, Weiguo Yin, Chang-De Gong Quantum confinement and interference often generate exotic properties in |
Monday, March 5, 2018 4:30PM - 4:42PM |
C18.00011: Chiral spin modes in doped graphene with Rashba spin-orbit coupling Abhishek Kumar, Saurabh Maiti, Dmitrii Maslov Recently chiral spin modes have been observed on the surface states of 3D topological insulator, Bi2Se3. These modes have also been claimed to exist in the spin-orbit coupled two-dimensional Fermi liquid. Motivated by these observations, we investigate collective spin-excitations in doped graphene grown on transition metal dichalcogenide, e.g., WS2 , where the dominant spin-orbit coupling is of the Rashba type. We consider optical conductivity and spin-susceptibility of such a system and identify specific resonances. We study the effect of electron-electron interactions on these observables and find that it couples spin and pseudo spin degrees of freedom, which were otherwise decoupled. This leads to interesting features like the modification of Rashba continuum as well as the breaking of degeneracy of the collective mode outside the continuum. |
Monday, March 5, 2018 4:42PM - 4:54PM |
C18.00012: Low-disorder artificial graphene in nano-patterned triangular antidot lattice of GaAs Heterostructure Lingjie Du, Sheng Wang, Loren Pfeiffer, K West, Saeed Fallahi, Michael Manfra, Vittorio Pellegrini, Shalom Wind, Aron Pinczuk Artificial graphene (AG) in semiconductors have been realized with honeycomb dot lattices [1] on 2D electron systems in GaAs quantum well to serve as advanced quantum simulators for probing novel electron behavior. Small period triangular antidot lattices, where well-defined massless Dirac fermions occur, have not been realized. Here, we report on recent experiments in low-disorder triangular antidot lattice and exploration of collective modes in created electron states by optical spectroscopy experiments using photoluminescence and resonant inelastic light scattering (RILS) at low temperature[2]. Using the cutting-edge fabrication technology, we fabricated small-period triangular antidot lattice (as small as 70 nm), which has an effective honeycomb lattice constant of about 40nm, on GaAs quantum well. In the RILS measurement, the massless Dirac fermions are clearly revealed by the intersubband transition and low energy transitions, well described by modeling the AG band structure. Interplay between quasiparticle interactions and lattice topology will be discussed. [1] S. Wang, et al. accepted in Nature nano. [2] L. Du, et al., in preparation. |
Monday, March 5, 2018 4:54PM - 5:06PM |
C18.00013: Enhanced electrochemical and thermal transport performance of Graphene/MoS2 heterostructures for lithium ion battery: multi-scale modeling Feng Gong, Dawei Xia, Mengqiang Wu, Jiaxuan Liao, Ziqiang Xu, Dimitrios Papavassiliou Graphene/molybdenum disulfide (Gr/MoS2) composites have exhibited superb electrochemical performance in lithium ion batteries (LIBs), yet the mechanisms have not been well studied. Here, we adopt multi-scale modeling to investigate the enhanced electrochemical and thermal transport properties of Gr/MoS2 heterostuctures. The calculated electronic structures demonstrated the greatly improved electrical conductivity of Gr/MoS2 heterostructures than pure MoS2 monolayers by the addition of graphene. With the increase of graphene concentration, graphene layers not only further improve the electrical conductivity, but also significantly stabilize the Li atoms in heterostructures. The calculated thermal conductivity form large scale molecular dynamic simulations manifested that the Gr/MoS2 heterostructures could achieve a much higher in-plane thermal conductivity compared to pure MoS2, which may accelerate the heat conduction from the electrode to the ambient, inducing excellent battery performances. Our findings not only shed light on the mechanisms of the enhanced electrochemical and thermal transport properties of Gr/MoS2 heterostructures, but also suggest how to design advanced Gr/MoS2 composites for LIBs. |
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