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 C45: Dirac and Weyl semimetals: Theory IILive
|
Hide Abstracts |
Sponsoring Units: DCMP Chair: Brian Skinner, Ohio State Univ - Columbus |
Monday, March 15, 2021 3:00PM - 3:12PM Live |
C45.00001: Randomness Models of Dilute Impurities Determine the Fate of Quantum-Criticality in 3D Dirac Semimetals João Santos Pires, Bruno Amorim, Aires Ferreira, Inanc Adagideli, Eduardo R Mucciolo, João Manuel Viana Parente Lopes Nodal 3D electron gases have received renewed attention in recent years with the discovery of Dirac-Weyl semimetals. An outstanding issue is the lift of the nodal density of states (NDoS) by weak disorder. A semimetal-to-metal transition was expected at finite disorder, but recent analytical/numerical work [1] had contradictory conclusions swinging between this scenario and an “avoided quantum-criticality” one. |
Monday, March 15, 2021 3:12PM - 3:24PM Live |
C45.00002: Fluctuation of Chern Numbers in Parametric Random Matrix Models Hung-Hwa Lin, Wei-Ting Kuo, Daniel Arovas, Yizhuang You Many Weyl semimetal materials contain a large number of Weyl points in their Brillouin zone, which prompts a description in terms of parameterized random matrices. Following early work of Wilkinson and coauthors, we consider such a model with three periodic parameters {\vec X} and investigate the eigenspectrum and the statistics of degeneracy points, to which can be associated an integer “charge”. The total charge in a “filled torus” with radial $X_3$ direction has the interpretation of a Chern number, and we investigate the statistics of this as a function of the thickness, confirming a saturation behavior beyond an initial diffusive regime. We propose a model to explain the correlations among the degeneracy points. |
Monday, March 15, 2021 3:24PM - 3:36PM Live |
C45.00003: Spin density wave order in interacting type-I and type-II Weyl semimetals Sarbajaya Kundu, David Senechal Weyl semimetals (WSM) have emerged as an excellent platform for studying the interplay of electronic interactions and topology. In this context, we have recently studied the effect of a local repulsive interaction on an inversion-symmetry breaking Weyl semimetal model, using the Cluster Dynamical Mean Field theory (CDMFT) and Variational Cluster Approximation (VCA) methods. In this talk, I will discuss the results of our analysis, which reveals a continuous transition from the Weyl semimetal phase to a gapped spin density wave (SDW) ordered phase at a critical value of the interaction, determined by the band structure parameters. I will further discuss the effect of introducing a finite tilt in the linear dispersion, for accessing the type-II WSM regime, where the critical interaction strength is found to be significantly diminished, indicating a greater susceptibility towards interactions. I will illustrate the behavior of the double occupancy, the spectral function and the Berry curvature associated with the Weyl nodes, in both the semimetallic and the magnetically ordered states. Finally, I will present an interaction-induced phase diagram for the Weyl semimetal model, as a function of the tilt parameter. |
Monday, March 15, 2021 3:36PM - 3:48PM Live |
C45.00004: Quantum materials for dark matter detection Richard Geilhufe Quantum materials offer unique opportunities to search for light and very weakly interacting particles. This development has given new hope to the ongoing search for dark matter (DM) in a time when experimental nullresults mount increasing pressure on traditional models. The detection of sub-MeV DM particles with a typical velocity of v=10^-3 c in the solar neighborhood requires sensor materials sensitive to tiny energy excitations. I will discuss the formalism for DM measurement using small mass Dirac materials and show the identification of relevant using materials informatics [1]. To overcome impurity effects [2], we propose a novel discriminator for a dark matter detection signal against thermal noise based on a directional dependence of the dark matter signal due anisotropy [3]. |
Monday, March 15, 2021 3:48PM - 4:00PM Live |
C45.00005: Disorder driven multifractality transition in Weyl nodal loops Miguel Araujo, Miguel Gonçalves, Pedro Ribeiro, Eduardo Castro The effect of short-range disorder in a three dimensional nodal line |
Monday, March 15, 2021 4:00PM - 4:12PM Live |
C45.00006: Optical Absorption in Weyl Superconductors: Novel Surface-Bulk Response With and Without Disorder Tsz Chun Wu, Hridis Pal, Matthew Foster We study the optical absorbance in a p+ip Weyl superconductor (WSC) by investigating the interplay between bulk and surface states responses. WSCs harbor gapless chiral Majorana surface states that are topologically protected. We show that in the clean limit, a novel topological optical absorbance occurs due entirely to surface-bulk transitions, which manifest a characteristic absorption peak. In the presence of disorder, we study the optical conductivity of the bulk through the Keldysh response theory. For weak disorder, the bulk response is reminiscent of the Mattis-Bardeen result in dirty s-wave superconductors, although it is nonzero at zero temperature even when the frequency falls below twice the pairing gap (due to the gapless Weyl points). For stronger disorder, the bulk response becomes more Drude-like and the p-wave features of the response gradually disappear. In the weak disorder limit, the total absorbance of the system is governed by the combined effects from both the bulk and surface-bulk responses. The additional features stemming from the surface-bulk response can serve as an indicator for the presence of surface states in sufficiently clean systems. We discuss the relevance of our results to the potential WSC UTe2. |
Monday, March 15, 2021 4:12PM - 4:24PM Live |
C45.00007: Axionic band topology in inversion-symmetric Weyl-charge-density waves Barry Bradlyn, Benjamin Wieder, Kuan-Sen Lin In this talk, we use analytic and numerical methods to study both lattice-commensurate and incommensurate minimal (magnetic) Weyl-CDW systems. We show that, as a function of the CDW phase, the system transitions between two distinct inversion-symmetric topological phases, differing by a pi shift in the electromagnetic theta angle. Crucially, low-energy critical theory for the transition is that of an axion insulator (AXI), neither phase is itself AXI. Using symmetry indicators of band topology and non-abelian Berry phase, we demonstrate that our results generalize to multi-band systems with only two Weyl fermions, and explore the consequences for transport measurements. We extend our results to time-reversal invariant Weyl or Dirac-CDWs, showing that the CDW phase in these systems mediates a helical higher-order topological phase transition. We conclude with a discussion of the experimental implications of our findings. |
Monday, March 15, 2021 4:24PM - 4:36PM Live |
C45.00008: Optical Response from Charge-Density Waves in Weyl Semimetals Robert McKay, Barry Bradlyn Electron-phonon coupling has been predicted to influence magnetoelectric coupling in Weyl semimetals (WSM) through charge-density wave distortions. We investigate this current by calculating the collective mode contribution to response functions in quasi-1D lattice and continuous models of a time-reversal-breaking WSM coupled to charge-density wave order. We compare the collective mode contributions from the longitudinal conductivity in a WSM to the established 1D results at linear and nonlinear order. We pay particular attention to the role of symmetry in mediating the effects of both the sliding and amplitude collective modes. We find that with inversion symmetry there are non-vanishing currents generated by third order processes, including a material analog of a Higgs mechanism. We also show that tilting the linearly dispersing nodes of the WSM will enhance the sliding mode contribution to the longitudinal conductivity at zero frequency. |
Monday, March 15, 2021 4:36PM - 4:48PM Live |
C45.00009: Criticality of two-dimensional disordered Dirac fermions in the unitary class Bjoern Sbierski, Elizabeth J Dresselhaus, Joel Ellis Moore, Ilya Gruzberg Two-dimensional (2D) Dirac fermions are a central paradigm of modern condensed matter physics. |
Monday, March 15, 2021 4:48PM - 5:00PM Live |
C45.00010: Weak Antilocalization and Quantum Hall Effect in Bulk CaCuSb Single Crystal SOUVIK SASMAL, Rajib Mondal, Ruta Kulkarni, Vikram Tripathi, Bahadur Singh, Arumugam Thamizhavel The quantum Hall effect (QHE) in 3D solids is relatively unexplored in experiments due to the limited choice of viable candidate materials. Here, we report on the observation of weak antilocalization (WAL) and QHE followed by Shubnikov de-Haas (SdH) oscillations with oscillation frequency 314 T in bulk CaCuSb single crystal which crystallizes in the hexagonal structure (P63/mmc). One of the unique features of this crystal structure is that it possesses two Cu-Sb layers in the unit cell which act as the conduction channels. Significant anisotropy in electrical transport measurements along crystallographic a- and c- direction suggests the magneto-transport effect is due to charge diffusion on Cu-Sb planes but not along c- axis. A cusp like behavior in the low field region of magnetoresistance reveals WAL in this compound, as observed in ABC- type hexagonal structure CaAgBi [1]. Quantized Hall plateaus are observed in 1/ρxy vs 1/B plot which is attributed to the multiple 2D conduction channels in the system. First-principles calculations show that CaCuSb is a semimetal with dominant hole carriers at the Fermi level. Our study shows that CaCuSb can provide a unique platform to study QHE in high magnetic fields. |
Monday, March 15, 2021 5:00PM - 5:12PM Not Participating |
C45.00011: Competing orders at the interface of a bilayer Weyl system with Fermi arcs Ritajit Kundu, Rohit Mukherjee, Herb Fertig, Arijit Kundu We study interaction effects at the interface of two Weyl semimetals, each with multiple Fermi arc states on their surfaces. We consider competing spontaneous orderings in the ground-state, in particular charge density and inter-surface exciton condensation. The resulting phases offer rich physics which can depend strongly on the relative orientation of the Fermi arcs. |
Monday, March 15, 2021 5:12PM - 5:24PM Live |
C45.00012: Strain-Induced Landau Levels in Tilted Weyl Semimetals Yangjun Lee, Cheol-Hwan Park A Weyl semimetal is characterized by pairs of Weyl points, which are topologically protected band degeneracies. Weyl semimetals host interesting phenomena such as Fermi arc surface states and chiral anomaly. There have been fascinating theoretical studies on strained Weyl semimetals, e.g., Refs. [1-3]. In this talk, we expand these theories to tilted Weyl cone systems and present the results of our calculations on strained and tilted Weyl semimetals. |
Monday, March 15, 2021 5:24PM - 5:36PM Live |
C45.00013: Quasi one-dimensional Ta2Se8I under pressure: From Weyl semimetal to superconductor Dennis Nenno, Qingge Mu, Jonathan Curtis, Johannes Gooth, Claudia Felser, Sergey Medvediev, Prineha Narang Structurally chiral Ta2Se8I shows a Fermi surface purely composed by the cones of Weyl nodes close to the chemical potential, resulting in quasi one-dimensional physics. Most intriguing is the formation of a charge-density wave that gaps the Fermi surface Weyl points just below room temperature. The phase mode of the charge-density wave realizes axion electrodynamics, together with excotic magnetoelectric responses. Here, we present a study on the electronic properties of Ta2Se8I under pressure. Increasing pressure lowers this charge-density wave transition temperature and eventually introduces superconductivity. We show how the Fermi surface evolves when compressing the unit cell, deviating from its originally quasi one-dimensional form. For larger pressures, coupling between the Ta-Se-chains increases, eventually leading to the break-down of the charge density wave transition. We present the ab initio electronic structure for unit cells compressed by external pressure, phonon instabilities and the implication for the electromagnetic response in equilibrium. Further, we find that signatures of the topological chiral anomaly appear in the non-linear optical response of the phase mode. |
Monday, March 15, 2021 5:36PM - 5:48PM On Demand |
C45.00014: Quantum oscillation beyond the quantum limit in pseudospin Dirac materials Chunming Wang, Haizhou Lu, X. C. Xie Recently, many unexpected fine structures in electric, magnetic, and thermoelectric responses at extremely magnetic fields in topological materials have attracted tremendous interest. We propose a mechanism of quantum oscillation beyond the strong-field quantum limit for Dirac fermions. The amplitude of the oscillation is far larger than the usual Shubnikov–de Haas oscillation. The oscillation tends to be periodic in the magnetic field B, instead of 1/B. The period of the oscillation does not depend on the Fermi energy. These behaviors cannot be described by the famous Lifshitz-Kosevich formula. The oscillation arises from a mechanism that we refer to as the inversion of the lowest Landau level, resulting from the competition between the pseudospin Dirac-type Landau levels and real-spin Zeeman spitting beyond the quantum limit. This inversion gives rise to the oscillation of the Fermi energy and conductivity at extremely large magnetic fields. This mechanism will be useful for understanding the unexpected fine structures observed in the strong-field quantum limit in Dirac materials. |
Monday, March 15, 2021 5:48PM - 6:00PM On Demand |
C45.00015: Heterogeneous Magnetic Domains in a Noncentrosymmetric Ferromagnetic Weyl Semimetal Bochao Xu, Jacob D Franklin, Hung-Yu Yang, Fazel Tafti, Ilya Sochnikov Magnetic Weyl semimetals are predicted to host emergent electromagnetic fields at heterogeneous strained phases or at the magnetic domain walls. Tunability and control of the topological and magnetic properties is crucial for revealing these phenomena, which are not well understood or fully realized yet. Here, we use a scanning SQUID microscope to image spontaneous magnetization and magnetic susceptibility of CeAlSi, a noncentrosymmetric ferromagnetic Weyl semimetal candidate. We observe large metastable domains alongside stable ferromagnetic domains. The metastable domains most likely embody a type of frustrated or glassy magnetic phase, with excitations that may be of an emergent and exotic nature. We find evidence that the heterogeneity of the two types of domains arises from magnetoelastic or magnetostriction effects. We show how these domains form, how they interact, and how they can be manipulated or stabilized with estimated lattice strains on picometer levels. CeAlSi is a frontier material for straintronics in correlated topological systems. |
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