Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session W60: Weyl Semimetal, Transport IIFocus

Hide Abstracts 
Sponsoring Units: DMP Room: Mile High Ballroom 4A 
Friday, March 6, 2020 8:00AM  8:12AM 
W60.00001: Planar Hall effect in thin films of the 3D Dirac semimetal Cd_{3}As_{2} Manik Goyal, Timo Schumann, David Kealhofer, Susanne Stemmer Cd_{3}As_{2} is a 3D Dirac semimetal with doubly degenerate band crossings at isolated points in the bulk Brillouin zone. It can also host gapless surface states. In Dirac and Weyl semimetals, a giant planar Hall effect (PHE) has been predicted to be associated with the chiral anomaly. In this talk, we will discuss our measurements of the PHE in (001) and (112) oriented epitaxial thin films of Cd_{3}As_{2} having a wide range of film thicknesses. We show that the PHE depends sensitively on the Fermi level. Studies of films of different thickness allow us to distinguish the contributions of bulk and surface states. We will discuss the different mechanisms that give rise to the PHE in these films. 
Friday, March 6, 2020 8:12AM  8:24AM 
W60.00002: NMR Investigation of FieldInduced Energy Gap in Topological NodeLine Semimetal ZrGeSe Guoqing Wu, Shengtang Wan, Rongxing Cao, Jian Hu, Xianghua Zeng, yafang Xu, Jinbo Zhang, Lin Wang, Qiuliang Wang, Lei Guo, Renkui Zheng, Bing Wu The discovery of topological semimetals provides opportunities to explore the exotic properties of relativistic fermions in condensed matter. Among those materials, the nodalline semimetal represents a new type of topological quantum state which displays Dirac cones along a onedimensional line or a closed circle protected by combined symmetry of inversion and timereversal, in contrast with the Dirac or Weyl semimetals with discrete Dirac or Weyl cones. Here we report NMR investigation of fieldinduced energy gap in topological nodalline semimetals of ZrGeSe single crystals, with high magnetic field up to 16 T and high hydrostatic pressure up to 50 GPa. We found that the opening of the energy gap is driven by the magnetic fieldinduced antiferromagnetic (AFM) order, and the gap opening is highly restricted under high pressure. 
Friday, March 6, 2020 8:24AM  8:36AM 
W60.00003: Violation of Ohm`s law in a Weyl metal Dongwoo Shin, Jeehoon Kim Weyl metal is one of the topological nontrivial materials holding Weyl fermions which are massless and have a chirality. The Weyl metal has been described in terms of axion electromagnetism rather than in Maxwell electromagnetism, and has peculiar properties such as chiral anomaly, the presence of magnetic monopole in the reciprocal lattice space and negative longitudinal magneto resistance. In this presentation, by transportation experiment besides negative longitudinal magneto resistance, we observed ohm’s law was broken in the Weyl metal and carried experimental and theoretical analysis of the violation of ohm`s law [1]. 
Friday, March 6, 2020 8:36AM  8:48AM 
W60.00004: Interplay of Dirac Nodes and VolkovPankratov Surface States in Compressively Strained HgTe David Mahler, JulianBenedikt Mayer, Philipp Leubner, Lukas Lunczer, Domenico Di Sante, Giorgio Sangiovanni, Ronny Thomale, Ewelina M Hankiewicz, Hartmut Buhmann, Charles Gould, Laurens W Molenkamp With the advent of topological materials, the Weyl fermion, a massless particle once proposed to describe neutrinos, can now be investigated in condensed matter systems as Weyl semimetals, and their close cousins Dirac semimetals. The HgTe material system, as a prototypical topological insulator for transport studies, is ideally suited, as the tunability of the details of its band structure through strain engineering, and its Fermi level by gating provide unparalleled control for the investigation of Weyl/Dirac semimetals [1]. 
Friday, March 6, 2020 8:48AM  9:00AM 
W60.00005: Exploring broken timereversal symmetry in Cd_{3}As_{2}/(Ga,Mn)Sb Dirac semimetal/ferromagnetic semiconductor heterostructures Arpita Mitra, Run Xiao, Nitin Samarth Cd_{3}As_{2} has attracted attention as a canonical Dirac semimetal. In this study, we aim to break time reversal symmetry (TRS) in Cd_{3}As_{2} by interfacing with a ferromagnetic semiconductor, (Ga,Mn)Sb. We have grown epitaxial Cd_{3}As_{2} /(Ga,Mn)Sb bilayers using molecular beam epitaxy on GaSb (111) buffer layers deposited on GaAs (111)B substrates. Highresolution xray diffraction shows good crystalline quality of GaSb and Cd_{3}As_{2} layers with full width half maximum of rocking curves, 0.04° and 0.11°, respectively. Atomic force microscopy shows smooth surfaces of (Ga,Mn)Sb and Cd_{3}As_{2} with root mean square roughness ~ 1.3 nm. SQUID magnetometry reveals that (Ga,Mn)Sb films are ferromagnetic, while low temperature magnetoresistance data show that they are highly resistive for the Mn composition used. We report the temperature dependent magnetotransport properties in these Cd_{3}As_{2 }/(Ga,Mn)Sb heterostructures and investigate the magnetic proximity effect by varying the thickness of the Cd_{3}As_{2} layer. We are also exploring interfacing Cd_{3}As_{2} with other ferromagnetic semiconductors in order to find an efficient material for breaking TRS in Cd_{3}As_{2}. 
Friday, March 6, 2020 9:00AM  9:12AM 
W60.00006: Negative longitudinal magnetoresistance, anisotropic magnetoresistance, and planar Hall effect in epitaxial thin films of elemental Bismuth Eugene Ark, Deshun Hong, Terence BretzSullivan, Changjiang Liu, Shulei Zhang, Leena Aggarwal, Vidya Madhavan, Anand Bhattacharya Observations of negative longitudinal magnetoresistance (NLMR), anisotropic magnetoresistance (AMR), and the planar Hall effect (PHE) under an inplane magnetic field are often used as indications of nontrivial topology in nonmagnetic material systems. We show NLMR, AMR, and PHE in crystalline epitaxial thin films (< 50 nm) of elemental Bismuth (111) grown by molecular beam epitaxy on intrinsic GaAs (111) substrates. Films were characterized insitu using scanning tunneling microscopy to confirm topography and density of states. Furthermore, the thickness and temperature dependence of these phenomena are investigated, demonstrating a high degree of tunability. We posit that these observations may be due to the Rashba effect in the surface states of Bi (111), rather than any nontrivial topological effects. 
Friday, March 6, 2020 9:12AM  9:24AM 
W60.00007: Quantum Hall effect due to surface states in (001)plane cadmium arsenide thin films David Kealhofer, Luca Galletti, Timo Schumann, Alexey Suslov, Susanne Stemmer We report transport studies of gated Hall bar structures fabricated from (001)oriented epitaxial thin films of cadmium arsenide, a threedimensional Dirac semimetal, in magnetic fields up to 45 T. This orientation does not host Fermi arctype surface states because the Dirac nodes project onto the same point in the surface Brillouin zone. Recent developments in the growth of these layers have resulted in films with quantum mobilities exceeding 4,000 cm^{2}/Vs. We explain the quantum Hall effect, which prominently features plateaus at even and odd filling factors across a range of carrier density, in terms of a surface state different from the Fermi arctype states thought to exist on other surfaces, underlining differences between these measurements and those in the more widely studied (112)plane films. 
Friday, March 6, 2020 9:24AM  9:36AM 
W60.00008: Anomalous Hall Effect induced by extremely low field in ultra pure ZrTe_{5} Joshua Mutch, Paul Malinowski, Qianni Jiang, Zhaoyu Liu, Di Xiao, JiunHaw Chu ZrTe_{5} has gathered interest in recent years due to its nontrivial topology. In monolayer form, it is predicted to be a quantum spin hall insulator. In bulk, it is predicted to reside extremely close to a phase transition between a strong and weak topological insulator, with a 3D Dirac semimetal state at the boundary between these two phases. We report detailed measurements of the anomalous hall effect (AHE) in ultrapure, high mobility bulk ZrTe_{5}. We find the hall resistance saturates at an extremely low magnetic field ( B << 1T ), and remains at the saturation value for fields up to 32T. This AHE is present despite no evidence of magnetism in ZrTe_{5}. We investigate the AHE effect in ZrTe5 as a function of temperature, magnetic field angle, strain, and doping, and discuss the origins of this effect. 
Friday, March 6, 2020 9:36AM  9:48AM 
W60.00009: Epitaxial Growth and insitu magnetotransport of Na_{3}Bi – a 3D Dirac semimetal Dana Peirce, Igor Pinchuk, Ryan Muzzio, Simranjeet Singh, Jyoti Katoch 3D topological Dirac semimetals (TDS) such as Na_{3}Bi and Cd_{3}As_{2} possess Dirac nodes located outside the timereversal invariant momentum points in the Brillouin zone. Recent theoretical and experimental work shows that quantum confinement of 3D TDS can open a tunable bulk bandgap and give rise to thicknessdependent alternate transitions between trivial and quantum spin Hall insulator states. In this talk, we will present our results on ultrathin growth of Na_{3}Bi films on insulating substrates using molecular beam epitaxy (MBE). We will also discuss our efforts towards angledependent highfield insitu magnetotransport measurements on backgated thin films of Na_{3}Bi. 
Friday, March 6, 2020 9:48AM  10:00AM 
W60.00010: Evolution of the electronic structure of the Weyl semimetal TaAs under pressure Zuzana Medvecka, Marcel Naumann, Marcus P. Schmidt, Vicky Süß, Helge Rosner, Michael Nicklas, Elena Hassinger Weyl semimetals provide ideal condensed matter platform to study Weyl fermions. When current and magnetic field are parallel in such systems, the chiral anomaly is expected to induce a negative longitudinal magnetoresistance. To observe this special feature the Fermi level must be close to the band crossing points (Weyl nodes) where quasiparticles behave like Weyl fermions [1]. 
Friday, March 6, 2020 10:00AM  10:36AM 
W60.00011: The chiral qubit: quantum computing with chiral anomaly Invited Speaker: Qiang Li The quantum chiral anomaly enables a nearly nondissipative current in the presence of chirality imbalance. We propose to utilize the chiral anomaly for the designs of qubits potentially capable of operating at THz frequency and at room temperature with a coherence time to gate time ratio of about 10^{4}. The proposed “Chiral Qubit” is a micronscale ring made of a Weyl or Dirac semimetal, with the 0〉 and 1〉 states corresponding to the symmetric and antisymmetric superpositions of chiral currents circulating along the ring clockwise and counterclockwise. A fractional magnetic flux through the ring induces a quantum superposition of the 0〉 and 1〉quantum states. The entanglement of qubits can be implemented through the nearfield THz frequency electromagnetic fields (EMF). We show that the Hamiltonian of the chiral qubit is similar to that of the superconducting qubit. This means that quantum gates can be implemented in a traditional way, and the algorithms developed for superconducting quantum processors will apply. Lightdriven (THz) ultrafast topology switching, demonstrated experimentally in Dirac/Weyl semimetal recently, will be discussed. 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2023 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700