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 M43: Dirac and Weyl Semimetal: Material Discovery and DevelopmentFocus
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Sponsoring Units: DMP Chair: Akshay Murthy, Fermi National Accelerator Laboratory Room: Room 317 |
Wednesday, March 8, 2023 8:00AM - 8:36AM |
M43.00001: Simple Chemical Rules for Predicting Band Structures of Kagome Materials Invited Speaker: Milena Jovanovic The kagome lattice, a hexagonal net of triangles, can host Dirac electronic states. However, rise of Dirac electronic states in compounds featuring the kagome lattice depends on the chemical bonding within a material. Starting from 3742 known compounds with the kagome lattice, we combine chemical heuristic, electric-structure calculations, and geometric considerations to create simple rules predicting if the low-energy physics of a compound will be dictated by the bonding within the kagome lattice. |
Wednesday, March 8, 2023 8:36AM - 8:48AM |
M43.00002: Discovery of a Two-Dimensional Weyl Semimetal Qiangsheng Lu, Guang Bian, Jacob L Cook The discoveries of Dirac semimetals in graphene and bulk Weyl semimetals in TaAs have led to an exciting territory of modern condensed matter physics where many emergent phases are generated from the interplay of quantum mechanics, relativity, and topology. So far, a two-dimensional (2D) variant of Weyl semimetals remains elusive for the instability of linear band crossings in reduced dimensions. In this work, we report the realization of a 2D Weyl semimetal in epitaxial bismuthene film. The Weyl fermion states originated from the gapped Dirac cones of bismuthene under the influence of symmetry-breaking substrate effects. Our high-resolution photoemission measurement shows a gapless dispersion and a clean Fermi surface. The spin polarization of the Weyl fermion states is observed in spin-resolved photoemission measurements. The bulk band topology of Weyl cones guarantees the existence of a new type of boundary mode, which is a 1D analog of Fermi arc states. These results establish epitaxial bismuthene as an ideal 2D Weyl semimetal that provides a unique platform for the experimental study of Weyl fermion states in low dimensions. |
Wednesday, March 8, 2023 8:48AM - 9:00AM |
M43.00003: Discovery of strong type-I Weyl semimetal features in an antiferromagnetic full-Heusler compound Davide Grassano, Luca Binci, Nicola Marzari Weyl semimetals are a class of topological semimetals with linear band crossings close to the Fermi level displaying non-trivial chirality, leading to the emergence of several exotic physical properties [New J. Phys. 9.9 (2007):356, Rev. Mod. Phys. 90.1 (2018):015001]. In order for such crossings to exist, either time-reversal or inversion symmetry must be broken [PRB 83.20 (2011): 205101]. Here, we report our discovery of a novel inversion-breaking Weyl semimetal in a full-Heusler compound with several features that are comparatively more intriguing than other inversion-breaking Weyl semimetals. In particular, the distance between two neighboring nodes is large enough to enable a wide range of linear dispersions. Also, only one kind of node can be identified; together with the lack of other trivial points ensures that the low-energy properties of the material are directly related to the presence of the Weyl nodes. |
Wednesday, March 8, 2023 9:00AM - 9:12AM |
M43.00004: Multi-gap Euler topology in materials Bartomeu Monserrat, Bo Peng, Siyu Chen, Adrien Bouhon, Robert-Jan Slager Multi-gap Euler topology has recently emerged as new direction in the study of topological matter. In these systems, the energy spectrum is divided into three or more groups of bands, and C2T or PT symmetries enforce real Hamiltonians. The resulting system can be characterised using the Euler class, and these phases host exotic phenomena such as bulk band nodes carrying non-Abelian charges. Despite growing interest, the experimental observation of multi-gap topology in real materials is still missing. In this talk, I will propose several materials exhibiting multi-gap topology, with examples in both the electronic and phonon sectors. In particular, I will highlight that phonons could be an ideal platform for the exploration of multi-gap topology in real materials, and discuss associated experimental signatures for their observation. |
Wednesday, March 8, 2023 9:12AM - 9:24AM |
M43.00005: Topological Dirac Semimetal BaAuSb Zhixiang Hu Dirac semimetals feature Dirac cones with topologically non-trivial states in the bulk that are protected by crystalline symmetries. They attract considerable attention due to rich quantum states and properties of interest, such as high Fermi velocities, mobility and small effective masses. In my talk I will show that ternary intermetallic BaAuSb crystal hosts both trivial and non-trivial topological Dirac states in the bulk. The non-trivial Fermi surface pocket at the Brillouin zone center is characterized with only few hundredths of the bare electron mass and with very high mobility. All parts of Fermi surface detected by quantum oscillations, topologically trivial or non-trivial have carriers with unusually high Fermi velocities and small masses. |
Wednesday, March 8, 2023 9:24AM - 9:36AM |
M43.00006: Tailoring Dirac states in a correlated system by chemical substitution Niloufar Nilforoushan, Michele Casula, Adriano Amaricci, Marco Caputo, Evangelos Papalazarou, Luca Perfetti, Ivana Vobornik, Pranab Das Kumar, Jun Fujii, David Santos-Cottin, Yannick Klein, Michele Fabrizio, Andrea Gauzzi, Marino Marsi In the vast domain of topological materials, the study of underlying mechanisms leading to the formation of nontrivial electronic band structures is key to discovering new topological electronic states [1]. In these systems, the control and manipulation of Dirac fermions also constitute a fundamental step toward the realization of novel electronic and spintronic devices. |
Wednesday, March 8, 2023 9:36AM - 9:48AM |
M43.00007: Crystal growth of emerging chiral materials Ag3AuSe2 and (Nb4Se15I2)I2 Daniel P Shoemaker Chiral symmetry is a requirement for the formation of Weyl points, while a material with accessible Weyl physics should also have a low density of states near the Fermi energy. By efficiently exploring chemical space experimentally, and evaluating calculated band structures, our group is working to increase the population of materials that exhibit Weyl-point-driven physics. We will present characterization of two chiral semiconductors. Cubic Ag3AuSe2 forms large crystals with millimeter size and a direct band gap concentrated around its Γ point, and our ability to tune this gap is probed by transport measurements. Separately, the chain compound (Nb4Se15I2)I2 is part of a materials class that includes the popular Weyl compound (TaSe4)2I. In (Nb4Se15I2)I2, individual chains are chiral but their stacking leads to a c-glide that removes chirality of the structure as a whole. It forms long needles with semiconducting transport. Next steps for engineering and utilizing these materials will be presented. |
Wednesday, March 8, 2023 9:48AM - 10:00AM |
M43.00008: BiAs as a Weyl semimetal Muhammad Zubair, Shoaib Khalid, Anderson Janotti Bismuth belongs to the group-V in the Periodic Table, yet it is often found as a trivalent atom in compounds such as Bi2Se3 and Bi2Te3. It features a strong spin-orbit coupling, leading to non-trivial topological band structure in many Bi-containing compounds, including Bi2Se3 and LuBi. Here we explore BiAs as a novel topological material. Using density functional theory calculations and testing the various functionals, we predict the lowest energy structure of BiAs and its band structure. We find that BiAs is a trivial semimetal but at the brink of becoming a Weyl semimetal. We predict a transition at 2 GPa with band crossing along L and M/2 of the hexagonal Brillion zone, and another at 8 GPa with crossing along L and H/2 points. We find a total of 12 pairs of Weyl points including 12 nodes and 12 anti-nodes. We also predict that a ferroelectric polarization can used to tune the spintronic properties in BiAs thin films. The chirality of the Weyl points can be switched by applying external electric filed. The link between pressure and electric field can be used to alter the spin texture of the bulk BiAs system. These novel features make this material attractive for spintronic based devices. |
Wednesday, March 8, 2023 10:00AM - 10:12AM |
M43.00009: Double Superconductivity in Topological Nodal-line Semimetal NaAlSi Shinya Uji, Takako Konoike, Yuya Hattori, Taichi Terashima, Tamio Oguchi, Takahiro Yamada, Daigorou Hirai, Toshiya Ikenobe, Zenji Hiroi In topological materials, peculiar surface states protected by crystal symmetries have attracted great interest because of unprecedented correlation with superconductivity. A topological nodal-line semimetal with a layered structure, NaAlSi shows bulk superconductivity at Tc = 6.8 K. The magnetic torque curves as a function of the field angle in the superconducting state of NaAlSi are found to show double superconductivity; a large broad diamagnetic signal arising from the bulk superconductivity and a small sharp signal observed only in magnetic fields nearly parallel to the layers. The sharp signal is ascribed to highly two-dimensional superconductivity with the similar Tc, whose thickness is only several times of the c-axis lattice constant 0.736 nm. The band structure calculations show the presence of large Fermi lines on the (001) plane, mainly formed by the surface Si p bands. The results show that the sharp signal is likely ascribed to the (001) surface superconductivity, which will open new perspectives in topological materials. |
Wednesday, March 8, 2023 10:12AM - 10:24AM |
M43.00010: ARPES study of f-electron Weyl Semimetal CeCoGe3 Robert Prater, Matthew C Staab, Sudheer Anand Sreedhar, Vsevolod Ivanov, Zihao Shen, Valentin Taufour, Sergey Y Savrasov, Inna M Vishik Strongly correlated electron systems and topological quantum materials each exhibit novel electronic excitations of great interest to modern science. Materials which combine both attributes offer unique insight into the robustness of topological structures when exposed to strong electron interactions. CeCoGe3 is a Weyl semimetal (WSM) with enhanced effective mass and low-temperature magnetism. It has predicted Weyl points and nodal lines whose positions and presence depends strongly on electronic correlations. I will present the first angle resolved photoemission spectroscopy (ARPES) measurements on CeCoGe3 which highlight the topological features of this compound, heavy fermion physics, and the interplay of these two. |
Wednesday, March 8, 2023 10:24AM - 10:36AM |
M43.00011: An Investigation of Magnetic Alloys of PtTe2 and PdTe2 using Angle Resolved Photoemission Spectroscopy (ARPES) Derek C Bergner, Ivan Pelayo, Warren L Huey, Archibald . Williams, Ziling Deng, Luca Moreschini, Jonathan D Denlinger, Alessandra Lanzara, Wolfgang E Windl, Joshua E Goldberger, Claudia Ojeda-Aristizabal With the emergence of two-dimensional materials with long-range magnetic ordering such as CrI3 and Cr2Ge2Te6, interest has grown towards new air-stable two-dimensional ferromagnets. Here we present an investigation into the valence band structure of 2 families of transition metal dichalcogenides, CrxPt1-xTe2 and CrxPd1-xTe2 grown by the Goldberger group at Ohio State University, using Angle Resolved Photoemission Spectroscopy (ARPES). PdTe2 and PtTe2 are reported as type-II Dirac Semimetals1,2 and with chromium substitution, these materials have the potential to preserve some of their topological properties, while remaining air-stable, and possibly ferromagnetic to the monolayer. We perform an ARPES study that utilizes different light polarizations and energies of synchrotron light. |
Wednesday, March 8, 2023 10:36AM - 10:48AM |
M43.00012: Coexistence of massless and massive Dirac fermion in surface doped black phosphorus near insulator-semimetal phase transition Wei Jie Chan, Yee Sin Ang, Lay Kee R Ang The coexistence of massless and massive Dirac fermions has remained elusive to date. Currently, this phenomenal was only realized in graphite, symmetry-broken bilayer graphene and topological crystalline insulator Pb1-xSnxSe. Here, we proposed a new candidate – surface doped black phosphorus that preserves space-time inversion symmetry, which guarantees the stability of the Dirac point, leading to an insulator-semimetal phase transition without gapping. Beyond a critical surface doping value, band inversion occurs with two separate Dirac points, which allows the system to exhibit either a massive, semi-Dirac or massless Klein tunnelling. Furthermore, we show that this elusive behaviour can be portrayed in electronic conductance and Fano factor measurements. Strikingly, this phenomenal can be generalized to any system that can be described by the universal type I semi-Dirac Hamiltonian. |
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