Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session R11: 2D Materials and Heterostructures |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Oscar Avalos Ovando, Ohio University Room: BCEC 152 |
Thursday, March 7, 2019 8:00AM - 8:12AM |
R11.00001: A first-principles study of the ferroelectricity of two-dimensional IV-VI group compounds Fen Xiong, Xilin Zhang, Zhen Lin, Yue Chen Two-dimensional (2D) ferroelectric materials with atomic thickness have attracted much research interest due to their potential industrial applications. The recent successful synthesis of 2D SnTe, which exhibits a spontaneous polarization along the in-plane directions, motivates further studies of the related 2D IV-VI group compounds. In this work, we focus on the theoretical calculations of the stability and ferroelectricity of 2D IV-VI compounds based on density functional theory (DFT) and the Berry phase method. Firstly, the energies of the competing 2D crystal structures of the IV-VI compounds have been computed from DFT; it is found that different structures are adopted by the 2D IV-VI compounds. To facilitate the engineering of the crystal structure, the alloying effects on the phase stability and the corresponding electronic origins have been further studied. Secondly, the spontaneous polarization is calculated using the Berry phase approach, and it is found that some of the 2D IV-VI compounds have more robust ferroelectricity than others. Moreover, the manipulation of spontaneous polarization via external strain has also been discussed. |
Thursday, March 7, 2019 8:12AM - 8:24AM |
R11.00002: Van der Waals induced rippling and anisotropy in the natural superlattice Franckeite Pablo San-Jose, Riccardo Frisenda, Ioanna Urban, Michal Baranowski, Nikos Papadopoulos, Herre S.J. van der Zant, Gabriel Sánchez-Santolino, Mar García-Hernández, Paulina Plochocka, Andres Castellanos-Gomez Franckeite, a naturally occurring van-der-Waals hetereostructure, is composed of alternating pseudohexagonal and pseudotetragonal two-dimensional layers. While both types of layers are in principle mechanically and electrically isotropic in the plane, Franckeite, like its cousin Cylindrite, exhibits a characteristic rippling pattern, the origin or which has remained unclear. Here we show, using continuum elasticity theory, that rippling is ultimately the result of a mechanical instability produced by a one-dimensional moiré superlattice forming in Franckeite's interlayer alignment. We also show that the ripples give rise to marked anisotropies in the electrical and optical sectors, as measured by differential reflectance, polarised Raman spectroscopy and electrical transport measurements. This picture connects the properties of bulk Franckeite to the basic mechanisms governing low-angle moiré multilayers, such as twisted graphene bilayers. |
Thursday, March 7, 2019 8:24AM - 8:36AM |
R11.00003: Layer Dependent MCD on Van der Waal-like 2D ferromagnetism Yu-Che Chiu, Zhenguang Lu, Daniel A Rhodes, Yuxuan Jiang, Dmitry Smirnov, James Hone, Luis Balicas The layered ferromagnetic semiconductor CrSiTe3 is a promising candidate for spintronic applications. According to DFT calculations, its bulk bandgap is predicted to be ~0.4 eV; meanwhile, a Curie temperature of ~33 K was reported, thus providing evidence for bulk ferromagnetism. More importantly, due to the van der Waal-like interlayer coupling, CrSiTe3 is exfoliable and possible to achieve monolayers through mechanical exfoliation making it appealing for 2D spintronics. However, the fundamental properties of CrSiTe3 have not been thoroughly studied, particularly in the few layers limit. . A number of of theoretical reports, suggest that the monolayer could have a larger bandgap but the presence of magnetism is still debatable (FM or AFM order). Nonetheless, among these predictions, the common agreement is that the decisive factor causing FM- or AFM-exchange coupling is the distance between Cr-Te-Cr bonds, which indicates that the spin configuration is closely related to the lattice. Therefore, In order to study the presence of magnetism and to understand the role spin-phonon interaction, we performed layer-dependent magnetization measurements via the magnetic circular dichroism (MCD) and Raman spectroscopy at different Ts. |
(Author Not Attending)
|
R11.00004: Strain induced half-semiconductor to half-metallic transition in 2D magnet CrI3 : A DFT approach Tista Mukherjee, Suman Chowdhury, Debnarayan Jana, Lok Lew Yan Voon
|
Thursday, March 7, 2019 8:48AM - 9:00AM |
R11.00005: Emission of Geometrically Modulated Monolayer Semiconductors I-Tung Chen, Chun An Chen, Tung-Han Yang, Kuan-Chang Chiu, Ying-Yu Lai, Yi-Hsien Lee Emission, including light and electrons, of the monolayer 2D lattices offers significant scientific interests in materials sciences and potential optoelectronics applications. |
Thursday, March 7, 2019 9:00AM - 9:12AM |
R11.00006: Barrier tunneling for the dice lattice under linearly-polarized light Dipendra Dahal, Godfrey Gumbs, Andrii Iurov, Danhong Huang We have investigated electron tunneling across a square barrier under external off-resonance dress- |
Thursday, March 7, 2019 9:12AM - 9:24AM |
R11.00007: Nonreciprocity in “motion” Tiago A. Morgado, Mario Silveirinha Lorentz reciprocity is intimately related to the linearity and invariance of Maxwell’s equations under time-reversal symmetry, and forbids one-way light flows in standard metal-dielectric platforms. Indeed, reciprocal systems are inherently bidirectional. Asymmetric light flows are typically obtained using a static magnetic bias. |
Thursday, March 7, 2019 9:24AM - 9:36AM |
R11.00008: Twisted-bilayer graphene devices fabricated with polymer-free graphene Rui Lyu, Dongying Wang, Emilio A Codecido, Kenji Watanabe, Takashi Taniguchi, Chun Ning Lau, Marc Bockrath The Mott-like insulator state and superconductivity realized by stacking two graphene sheets that are twisted near 1.1°, the “magic angle [1,2],” has stimulated a new wave of interest in this newfound material in the two-dimensional material family. We will present our recent work in fabricating twisted bilayer graphene heterostructures. Instead of using graphene exfoliated by tape, we obtain the graphene sheets by scratching thin graphite flake deposited on wafer with a razor blade. Combining with the pick-up technique[3], the graphene is free from any tape or polymer residue. Atomic force microscope images and transport measurements results indicate a high quality in the devices we made. Low temperature magnetoconductance measurements are also performed and the latest results will be discussed. [1] Y. Cao et al, Nature 556, 80-84(2018). [2] Y. Cao et al, Nature 556, 43-50 (2018). [3] L. Wang et al., Science 342, 614-617 (2013). |
Thursday, March 7, 2019 9:36AM - 9:48AM |
R11.00009: Electronic and Magnetic Properties of Patterned Hydrogenated Graphene: A First-principles Study Bi-Ru Wu Graphene is recognized as a promising 2D material with abundant physical properties, and flexibility in designing, but the zero band gap limited its applications. Graphane, a fully hydrogenated graphene, opens a remarkable energy gap. Furthermore, the hydrogenation also provide magnetic configuration of partial hydrogenated graphene due to the unpaired or localized electrons of unhydrogenated carbon atoms. In hydrogenated graphene, the carbon atoms of missing hydrogen atom prefer aggregate and form a cluster or zigzag chains. The former establishes a graphene quantum dot (GQD) embedded in graphane; the later is as a bare carbon chain or chains in graphane. We found the bare carbon chains and embedded GQDs can interact with each other. Such an inter-chain interaction and inter-dot affect the band structure of patterned hydrogenated graphene, and the inter-dot interaction will further change the magnetic properties of the embedded GQDs. It is interesting that the interaction changes the spin orientation of the atoms in the adjacent triangular GQDs and alters the energy dispersions. |
Thursday, March 7, 2019 9:48AM - 10:00AM |
R11.00010: Transport measurement of twisted bilayer-bilayer graphene Thao Dinh, Zhiren Zheng, Qiong Ma, Suyang Xu, Kenji Watanabe, Takashi Taniguchi, Pablo Jarillo-Herrero, Nuh Gedik The recent discovery of correlated insulator behavior and superconductivity in magic-angle graphene has attached tremendous interest in twisted van der Waals systems. So far, people have been focusing on the moiré superlattice and the flat band formed due to the interlayer coupling. In fact, twisting can be used to engineer the symmetry of a 2D system, which may lead to interesting phenomena that are not allowed in their natural form. In this work, we explore such broken symmetry effect in a twisted bilayer-bilayer graphene structure. The two bilayers are rotated with respect to each other by 180o. Based on the symmetry analysis, the twisted four-layer system is strongly inversion-broken and has an out-of-plane polar axis. We fabricated high quality dual-gated devices and we will report on the transport and optical behavior of this novel system. |
Thursday, March 7, 2019 10:00AM - 10:12AM |
R11.00011: Inter-Landau-level Andreev Reflection at the Dirac Point in a Graphene Quantum Hall State Coupled to a NbSe2 Superconductor MANAS SAHU, Xin Liu, Arup Kumar Paul, Sourin Das, Pratap Raychaudhuri, Jainendra Jain, Anindya Das Superconductivity and the quantum Hall effect are distinct states of matter occurring in apparently incompatible physical conditions. Recent theoretical developments suggest that the coupling of the quantum Hall effect with a superconductor can provide fertile ground for realizing exotic topological excitations such as non-Abelian Majorana fermions or Fibonacci particles. As a step toward that goal, we report observation of Andreev reflection at the junction of a quantum Hall edge state in a single layer graphene and a quasi-twodimensional niobium diselenide (NbSe2) superconductor. Our principal finding is the observation of an anomalous finite-temperature conductance peak located precisely at the Dirac point, providing a definitive evidence for inter-Landau-level Andreev reflection in a quantum Hall system. Our observations are well supported by detailed numerical simulations, which offer additional insight into the role of the edge states in Andreev physics. This study paves the way for investigating analogous Andreev reflection in a fractional quantum Hall system coupled to a superconductor to realize exotic quasiparticles. |
Thursday, March 7, 2019 10:12AM - 10:24AM |
R11.00012: Band structure tuning of doped Graphene/hBN heterostructure Hongyun Zhang, Eryin Wang, Shuopei Wang, Xiaobo Lu, Jonathan Denlinger, Alexei V Fedotov, Takashi Taniguchi, Guangyu Zhang, Shuyun Zhou Tuning Dirac electrons by a periodic potential is an important scientific question and graphene/h-BN is a model van der Waals heterostructure for investigating this. Here we report our recent ARPES progress on the electronic band structure of doped graphene/BN, which shows intriguing band structure engineering of both the valence and conduction bands. |
Thursday, March 7, 2019 10:24AM - 10:36AM |
R11.00013: Nonequilibrium noise measurements using hBN tunnel barriers Xuanhan Zhao, Panpan Zhou, Loah Stevens, Douglas Natelson Xuanhan Zhao1, Loah A. Stevens1, Panpan Zhou1, K. Watanabe2, T. Taniguchi2, Douglas Natelson1,3,4 |
Thursday, March 7, 2019 10:36AM - 10:48AM |
R11.00014: Imaging non-circular cyclotron orbits in a graphene/hBN superlattice Arthur Barnard, Aaron Sharpe, John Wallbank, Kenji Watanabe, Takashi Taniguchi, Vladimir Falko, David Goldhaber-Gordon When graphene is rotationally aligned with an underlying hexagonal boron nitride (hBN) substrate, a superlattice naturally forms. This drastically alters graphene’s electronic band structure, leading to minibands whose structure enables us to electrostatically tune the Fermi-surface size and shape. A striking consequence of altering the Fermi-surface shape is that electrons are no longer expected to follow circular cyclotron motion in the presence of a magnetic field. Transverse electron focusing (TEF) measurements have shown signatures of these non-circular orbits in a graphene/hBN superlattice, however, a direct probe has been lacking. |
Thursday, March 7, 2019 10:48AM - 11:00AM |
R11.00015: THz spectroscopy of graphene coupled to LaAlO3/SrTiO3 nanoscale junctions Erin Sutton, Lu Chen, Jianan Li, Qing Guo, Hyungwoo Lee, Jungwoo Lee, Chang-Beom Eom, Patrick Irvin, Jeremy Levy
|
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