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 E45: Electronic Structure of Topological SemimetalsLive
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Sponsoring Units: DCMP Chair: Claudia Felser, Max Planck Institute for Chemical Physics of Solids |
Tuesday, March 16, 2021 8:00AM - 8:12AM Live |
E45.00001: Nonsymmorphic Symmetry-Protected Band Crossings in a Correlated Metal Han Wu, Alannah Hallas, Xiaochan Cai, Jianwei Huang, Vaideesh Loganathan, Ashley Weiland, Gregory McCandless, Julia Y Chan, Sung-Kwan Mo, Donghui Lu, Makoto Hashimoto, Andriy Nevidomskyy, Gang Li, Emilia Morosan, Ming Yi Topological semimetals in which the bulk bands cross at points without opening an energy gap have emerged as a particularly rich platform to explore novel electronic phenomena. In nodal line semimetals, the bulk band linear crossings extend from discrete points to continuous lines or loops in momentum space. Crystalline symmetries, such as nonsymmorphic symmetry, can play a crucial role in protecting the band crossings along a continuous line or loop in momentum space in TSM. Nonsymmorphic symmetry will generate a band folding with crossings at the Brillouin zone (BZ) boundaries that are protected against spin orbital coupling. Here we will present our recent combined theory and angle-resolved photoemission spectroscopy study on PtPb4. We will show the existence of nonsymmorphic symmetry protected Dirac nodal lines in this material system as well as demonstrate the effect of moderate electron correlations on the measured band structure. |
Tuesday, March 16, 2021 8:12AM - 8:24AM Live |
E45.00002: STM/STS OF FEW-LAYER TOPOLOGICAL SEMIMETAL NiTe2 AT CRYOGENIC TEMPERATURES Stephanie Lough, Brandon T Blue, Duy Le, Talat Rahman, Masa Ishigami Nickel ditelluride (NiTe2) is a member of the transition metal dichalcogenide (TMD) family which has garnered interest due to predicted spin-polarized surface states near the Fermi level and the presence of Dirac nodes in its band structure. Recent angle-resolved photoemission spectroscopy (ARPES) results have observed some of these features but is limited in its ability to probe states above the Fermi level or to detect the influence of surface defects. In this work, exfoliation of bulk NiTe2 is performed under ultra-high vacuum (UHV) in order to generate a clean surface for scanning tunneling microscopy and spectroscopy (STM/STS) at cryogenic temperatures. Multiple peaks in the local density of electronic states (LDOS) are observed near the Fermi Level. To elucidate the nature of these features in the electronic structure, the LDOS is compared to calculated band structure obtained computationally from density functional theory (DFT) and to previous ARPES results. |
Tuesday, March 16, 2021 8:24AM - 8:36AM Live |
E45.00003: Detection of hole pockets in the candidate type-II Weyl semimetal MoTe2 from Shubnikov-de Haas quantum oscillations Yajian HU, Wing Chi Yu, Kwing To Lai, Dan Sun, Fedor F Balakirev, Wei Zhang, Jianyu Xie, Rajveer Jha, Ryuji Higashinaka, Tatsuma D. Matsuda, Youichi Yanase, Yuji Aoki, Swee K. Goh The bulk electronic structure of Td-MoTe2 features large hole Fermi pockets at the BZ center (Γ) and two electron Fermi surfaces along the Γ-X direction. However, the large hole pockets, whose existence has important implications for the Weyl physics of MoTe2, has never been conclusively detected in quantum oscillations. We report an unambiguous detection of these elusive hole pockets via Shubnikov–de Haas quantum oscillations. At ambient pressure, the quantum oscillation frequencies for these pockets are 988 and 1513T (B//c). Their large quasiparticle effective masses m* ndicating the importance of Coulomb interactions. Furthermore, at 13kbar, we detected a peak at 1798T, which experienced an amplitude enhancement relative to the low pressure data. This can be attributed to the reduced curvature of the hole pockets under pressure. Combining our data with DFT+U calculations, where U is the Hubbard parameter, our results shed light on why these important hole pockets have not been detected until now. |
Tuesday, March 16, 2021 8:36AM - 8:48AM Live |
E45.00004: Determination of the electron-phonon coupling with time-domain techniques reveal contrasting bond strengths in topological semimetal WTe2 Nicolas Gauthier, Hadas Soifer, Alexandre Gauthier, Idris Boukahil, C Das Pemmaraju, Edbert Jarvis Sie, Clara M Nyby, Aaron Lindenberg, Patrick S Kirchmann, Zhixun Shen We studied the electron and structural dynamics of the topological semimetal WTe2 using time- and angle-resolved photoemission spectroscopy (trARPES), ultrafast electron diffraction (UED) and density functional theory (DFT). We report the observation of band oscillations at multiple frequencies due to A1 coherent phonon modes. By isolating the effect of each phonon on the different electronic bands, we reveal the complexity of electron-phonon coupling in the electronic band structure. Combining these spectroscopic observations with UED results, we quantify the electron-phonon coupling strength in WTe2 for two A1 phonons and find that inter-layer modes are more weakly coupled than intra-layer modes. We explain this difference with the general expectation that Van der Waals bonds are weaker than covalent bonds. Our results impact the understanding how lattice structure determines electronic and topological properties. |
Tuesday, March 16, 2021 8:48AM - 9:00AM Live |
E45.00005: Phonon magnetochiral effect of band-geometric origin in Weyl semimetals Sanghita Sengupta, Nabil Lhachemi, Ion Garate The phonon magnetochiral effect consists of a nonreciprocity in the velocity or attenuation of acoustic waves when they propagate parallel and antiparallel to an external magnetic field. The first experimental observation of this effect has been reported recently in a chiral magnet and ascribed to the hybridization between acoustic phonons and chiral magnons. We present a potentially measurable phonon magnetochiral effect of electronic origin in chiral Weyl semimetals. Caused by the Berry curvature and the orbital magnetic moment, this effect is enhanced for longitudinal acoustic phonons by the chiral anomaly. Aditionally, we also report similar effects for the optical phonons. |
Tuesday, March 16, 2021 9:00AM - 9:12AM Live |
E45.00006: Anisotropic Linear Optical Properties and Optical Resonances in Weyl Semimetals Rui Zu, Mingqiang Gu, Lujin Min, Chaowei Hu, Ni Ni, Zhiqiang Mao, James M Rondinelli, Venkatraman Gopalan Since the first experimental discovery of Weyl semimetals, TaAs and NbAs have attracted significant attention due to their broken inversion symmetry and topological properties. Optical characterization serves as a powerful tool to probe electronic transitions in these systems. To understand optical response as a function of wavelength, the anisotropic dielectric functions and complex refractive indices serve as fundamental properties and vital pieces of the puzzle. |
Tuesday, March 16, 2021 9:12AM - 9:24AM Live |
E45.00007: Topological Lifshitz transitions and Fermi arc manipulation in Weyl semimetal NbAs Haifeng Yang, Lexian Yang, Zhongkai Liu, Yan Sun, Andrei B Bernevig, Claudia Felser, Binghai Yan, Yulin Chen Surface Fermi arcs (SFAs), the unique open Fermi-surfaces (FSs) discovered recently in topological Weyl semimetals (TWSs), are unlike closed FSs in conventional materials and can give rise to many exotic phenomena, such as anomalous SFA-mediated quantum oscillations, chiral magnetic effects, three-dimensional quantum Hall effect, non-local voltage generation and anomalous electromagnetic wave transmission. Here, by using in-situ surface decoration, we demonstrate successful manipulation of the shape, size and even the connections of SFAs in a model TWS, NbAs, and observe their evolution that leads to an |
Tuesday, March 16, 2021 9:24AM - 9:36AM Live |
E45.00008: Observation of multi-fermionic states in Ti2Te2P Gyanendra Dhakal, Md Mofazzel Hosen, Ashis K, Nandy, Alexandros Aperis, Klauss Dimitri, Pablo Maldonado, Christopher Sims, Firoza Kabir, Sabin Regmi, Yangyang Liu, Luis Persaud, Dariusz Kaczorowski, Peter Oppeneer, Madhab Neupane The advent of topological insulators (TIs) in a three-dimensional system followed by topological semimetallic states (TSMs) brought a paradigm shift in the understanding of the materials. Here we report the observation of the surface Dirac dispersion in a material Ti2Te2P at the M point of the Brillouin zone (BZ) in a tetradymite crystal structure employing angle-resolved photoemission spectroscopy (ARPES), which is in agreement with the first-principles calculations. Our study further reveals a Dirac cone dispersion at the Gamma-point of the BZ suggesting that this material holds multi-fermionic states. Our systematic studies open a platform to study the exotic properties of Dirac state in a single material. |
Tuesday, March 16, 2021 9:36AM - 9:48AM Live |
E45.00009: Studying ultrafast hot electron dynamics in topological nodal-line semimetal ZrSiS using XUV-based time- and angle-resolved photoemission spectroscopy Yangyang Liu, Md Mofazzel Hosen, Gyanendra Dhakal, Christopher Sims, John E Beetar, Sabin Regmi, Klauss Dimitri, Firoza Kabir, Dariusz Kaczorowski, Michael Chini, Madhab Neupane We study the ultrafast hot electron cooling process on topological nodal-line semimetal ZrSiS using an advanced XUV-based time- and angle-resolved photoemission spectroscopy (trARPES) with sub-30 meV energy resolution and 320 fs time resolution. By scanning the delay, the transient ARPES spectra on the nodal-line bulk states and surface states are measured, separately. We find that the relaxation decay of the transient electronic temperature in the nodal-line bulk states (around 700 fs) is longer than the surface states (around 320 fs). More interestingly, the relaxation process of the hot electron temperature in the nodal-line bulk states contains contributions from multiple channels. Our studies reveal the unique ultrafast properties of the hot electrons in the nodal-line semimetal ZrSiS. |
Tuesday, March 16, 2021 9:48AM - 10:00AM Live |
E45.00010: Kramers Nodal Line Metals Yingming Xie, Xuejian Gao, Xiao Yan Xu, Cheng-Ping Zhang, Jinxin Hu, Kam Tuen Law Recently, it was pointed out that all chiral crystals with spin-orbit coupling (SOC) are Kramers Weyl semimetals (KWSs) which possess Weyl points pinned at time-reversal invariant momenta (TRIMs). In this work, we show that all achiral non-centrosymmetric materials with SOC belong to a new class of topological materials, which we term Kramers nodal line metals (KNLMs). In KNLMs, there are doubly degenerate lines, which we call Kramers nodal lines (KNLs), connecting TRIMs. The KNLs create Dirac type band touching points at SOC split Fermi surfaces. Due to the touching points, the KNLs create two types of Fermi surfaces, namely, the spindle torus type and the octdong type, the latter of which is particularly interesting. All the states on the octdong Fermi surface are described by two-dimensional massless Dirac Hamiltonians. Therefore, materials with octdong Fermi surfaces support linear optical conductance in the bulk and quantized optical conductance in thin films. We further show that KNLMs can be regarded as parent states of KWSs. As an example, we demonstrate how a single Kramers Weyl point can be created near the Fermi energy by straining achiral BiTeI. Therefore, we conclude that all non-centrosymmetric metals with SOC are topological, as they are either KWSs or KNLMs. |
Tuesday, March 16, 2021 10:00AM - 10:12AM Live |
E45.00011: Using Chemical Pressure to Tune the Electronic State in the Topological Metal Zr2Te2P Oladehin Olatunde, Ryan Baumbach, David E Graf, Kaya Wei, Jorge Galeano-Cabral
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Tuesday, March 16, 2021 10:12AM - 10:24AM Live |
E45.00012: Two phase transitions driven by surface electron doping in WTe2 Antonio Rossi, Giacomo Resta, Seng Huat Lee, Ronald Dean Redwing, Chris Jozwiak, Aaron Bostwick, Eli Rotenberg, Sergey Savrasov, Inna Vishik Topological Weyl semimetal WTe2 is a Van der Waals crystal that gained attention for its large and nonsaturating magnetoresistance, which has been attributed to perfect compensation of electron and hole pockets in the bulk electronic structure. Although, altering the electron hole-balance via electron doping is not predicted to yield a structural phase transition, it is reasonable to expect a different electronic ground state with respect to the compensated system. |
Tuesday, March 16, 2021 10:24AM - 10:36AM Live |
E45.00013: Signatures of a topological Weyl loop in magnetic semimetal Co3Sn2S2 Zijia Cheng, Ilya Belopolski, Tyler Cochran, Stepan Tsirkin, Jiaxin Yin, Songtian Zhang, Xiaoxiong Liu, Guoqing Chang, Xian Yang, Daniel Multer, Timur Kim, Cephise Cacho, Claudia Felser, Titus Neupert, Hasan Zahid The search for novel topological phases of matter in quantum magnets has emerged as a frontier of condensed matter physics. Here we present our high-resolution angle-resolved photoemission spectroscopy results on single crystals of Co3Sn2S2 in its ferromagnetic phase. We report for the first time signatures of a topological Weyl loop. From fundamental symmetry considerations, this magnetic Weyl loop is expected to be gapless if the spin-orbit coupling(SOC) is strictly zero but gapped, with possible Weyl points, under finite SOC. We point out that high-resolution ARPES results to date cannot unambiguously resolve the SOC gap anywhere along the Weyl loop. As a result, we argue that from the point of view of photoemission spectroscopy the presence of Weyl points in Co3Sn2S2 remains ambiguous. We will also present our recent results on the tunability of the electronic structure in magnetic semimetal Co3Sn2S2. |
Tuesday, March 16, 2021 10:36AM - 10:48AM Live |
E45.00014: Intertwined non-trivial band topology and giant Rashba spin splitting in KSnSb1-xBix Chiranjit Mondal, Chanchal Barman, Aftab Alam, Biswarup Pathak Composite quantum compounds (CQCs) have become an important avenue for the investigation of intercorrelation between two apparently different fields of physics. Topological superconductors, axion insulators are few such CQCs which are recently drawing tremendous attention in the community. Topological nontriviality and Rashba spin physics are seemingly two incompatible quantum phenomena but can be intertwined within a CQC platform. We have presented a general symmetry based mechanism, supported by ab-initio calculations to achieve intertwined giant Rashba splitting and topological nontrivial states simultaneously in a single crystalline system. We have achieved Rashba splitting energy and Rashba coefficient values as large as 161 meV and 4.87 eV Å respectively along with Weyl semimetal phase in KSnSb0.625Bi0.375. These values are even larger than the values reported for widely studied topologically trivial Rashba semiconductor BiTeI. The beauty of our systematically analysis is that one can achieve various topological phase without compromising the Rashba parameters, in this CQC platform. |
Tuesday, March 16, 2021 10:48AM - 11:00AM Live |
E45.00015: Observation of Surface States in Concentric Nodal Line Semimetal Candidate ZrP2 Christopher Sims, Md Mofazzel Hosen, Firoza Kabir, Hugo Aramberri, Cheng-Yi Huang, Gyanendra Dhakal, Klauss Dimitri, Sabin Regmi, Xiaoting Zhou, Tay-Rong Chang, Hsin Lin, Dariusz Kaczorowski, Nicholas Kioussis, Madhab Neupane Topological semimetals have enhanced our understanding of topological states in condensed matter physics. In topological nodal line semimetals, conduction and valence bands cross each other along a closed curve in the three-dimensional Brillouin zone, where no perturbation can remove this crossing line and open a full direct gap between the two bands. These nodal lines are topologically protected by the symmetry group and can be associated with a topological invariant. Here, we present a systematic angle-resolved photoemission spectroscopy study of a topological nodal-line semi metallic state in the transition metal dipnictide ZrP2. Our study reveals the detailed electronic structure of ZrP2, which is protected by non symmorphic symmetry, more specifically the glide symmetry. Our findings reveal that that ZrP2 contains concentric intersecting coplanar ellipse (CICE) nodal lines. |
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