Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session F22: New developments in the Study of 3D Dirac and Weyl semimetalsInvited
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Sponsoring Units: DCMP Chair: Arun Bansil, Northeastern University Room: New Orleans Theater A |
Tuesday, March 14, 2017 11:15AM - 11:51AM |
F22.00001: Topological Materials Invited Speaker: Hsin Lin Topological materials host various novel quantum phases of electrons which are characterized by band topology and topologically protected surface/edge states. Despite recent progress, intense world-wide research activity in search of new classes of topological materials is continuing unabated. This interest is driven by the need for materials with greater structural flexibility and tunability to enable viable applications in spintronics and quantum computing. We have used first-principles band theory computations to successfully predict many new classes of 3D topologically interesting materials, including Bi2Se3 series, the ternary half-Heusler compounds, TlBiSe2 family, Li2AgSb-class, and GeBi2Te4 family as well as topological crystalline insulator (TCI) SnTe family and Weyl semimetals TaAs, SrSi2, (Mo,W)Te2, Ta3S2, and LaAlGe family. I will also highlight our recent work on 3D type-II Dirac semimetals in VAl3 family. [Preview Abstract] |
Tuesday, March 14, 2017 11:51AM - 12:27PM |
F22.00002: Topological Electronics States and Materials Invited Speaker: Zhong Fang The rapid development in the field of topological states is due both to conceptual theoretical advances, and to the discoveries of realistic materials where these exotic states can be hosted. First principles calculations play important roles in this field. On the theoretical front, the calculations and understanding of Berry curvature and gauge field established the connection between topology and electronic structures. On the experimental side, most of materials discovered up to now in this field are stimulated by computational predictions. In this talk, I will review recent progresses in this field, with focus on topological semimetals, and address some recent theoretical and experimental results. [Preview Abstract] |
Tuesday, March 14, 2017 12:27PM - 1:03PM |
F22.00003: Relativistic Fermions Generated by Square Lattices in Layered Compounds Invited Speaker: Zhiqiang Mao Recent discoveries of topological semimetals have generated immense interests since they represent new topological states of quantum matters. In this talk, I will present our recent studies on topological semimetals [1-4], which are focused on Dirac/Weyl fermions generated by square lattices in layered compounds. I will first report on our discoveries of two new Dirac materials Sr1-yMn1-zSb2 [1] and BaMnSb2 [2] in which nearly massless Dirac fermions are generated by 2D Sb layers. In Sr1-yMn1-zSb2, Dirac fermions are found to coexist with ferromagnetism, offering a rare opportunity to investigate the interplay between relativistic fermions and spontaneous time reversal symmetry breaking and explore a possible magnetic Weyl state. Then I will show our quantum oscillation studies on two new Dirac nodal line semimetals -- ZrSiSe and ZrSiTe [3]. We have not only revealed their signatures of nodal-line fermions, but also demonstrated that their atomically thin crystals are accessible via mechanical exfoliation, raising the possibility of realizing the theoretically predicted 2D topological insulators [5]. Finally I will discuss exotic quantum transport behavior arising from the zeroth Landau level in Weyl semimetal YbMnBi$_{\mathrm{2}}$ [4,6]. References: [1] Liu et al., arXiv:1507.07978. [2] Liu et al., Sci. Rep. 6, 30525 (16). [3] Hu et al., PRL \textbf{117}, 016602 (16). [4] Liu et al., arXiv: 1608.05956 [5] Q. Xu et al., PRB 92, 205310 (15). [6] Borisenko et al., arXiv: 1507.04847 (12). [Preview Abstract] |
Tuesday, March 14, 2017 1:03PM - 1:39PM |
F22.00004: Chiral Magnetic Effect in Condensed Matters Invited Speaker: Qiang Li The chiral magnetic effect is the generation of electrical current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum chiral anomaly in systems possessing charged chiral fermions. In quark-gluon plasma containing nearly massless quarks, the chirality imbalance is sourced by the topological transitions. In condensed matter systems, the chiral quasiparticles emerge in the 3D Dirac and Weyl semimetals having a linear dispersion relation. Recently, the chiral magnetic effect was discovered in a 3D Dirac semimetal - zirconium pentatelluride, ZrTe$_{5}$, in which a large negative magnetoresistance is observed when magnetic field is parallel with the current [Li et al - arXiv:1412.6543, Nature Physics - doi:10.1038/nphys3648)]. It is now reported in more than a dozen Dirac and Weyl semimetals. Broadly speaking, the chiral magnetic effect can exist in a variety of condensed matters. In some cases, a material may be transformed into a Weyl semimetal by magnetic field, exhibiting the chiral magnetic effect. In other cases, the chiral magnetic current may be generated in magnetic Dirac semimetals without external magnetic field, or in asymmetric Weyl semimetals without electric field where only a magnetic field and the source of chiral quasipartiles would be necessary. In the limit of conserved quasiparticle chirality, charge transport by the chiral magnetic current is non-dissipative. The powerful notion of chirality, originally discovered in high-energy and nuclear physics, holds promise in new ways of transmitting and processing information and energy. At the same time, chiral materials have opened a fascinating possibility to study the quantum dynamics of relativistic field theory in condensed matter experiments. [Preview Abstract] |
Tuesday, March 14, 2017 1:39PM - 2:15PM |
F22.00005: Electronic properties of new topological quantum materials Invited Speaker: Adam Kaminski Topological materials are characterized by the presence of nontrivial quantum electronic states, where often the electron spin is locked to its momentum. This opens up the possibility for developing new devices in which information is processed or stored by means of spin rather than charge. In this talk we will discuss the electronic properties of several of newly discovered topological quantum materials. In WTe2 we have observed a topological transition involving a change of the Fermi surface topology (known as a Lifshitz transition) driven by temperature. The strong temperature-dependence of the chemical potential that is at the heart of this phenomenon is also important for understanding the thermoelectric properties of such semimetals. Both WTe2 and MoTe2 were proposed to host type II Weyl semimetalic state. Indeed our data provides first experimental confirmation of such state in both of these materials. We will also present evidence for a new topological state in PtSn4 where pairs of extended Dirac node arcs rather are present rather than Dirac points, that is so far not understood theoretically. Our research opens up new directions on enhancing topological responsiveness of new quantum materials. [1] Yun Wu, Daixiang Mou, Na Hyun Jo, Kewei Sun, Lunan Huang, S. L. Bud'ko, P. C. Canfield, and Adam Kaminski, Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe2. Phys. Rev. B 94, 121113(R) (2016) [2] Lunan Huang, Timothy M. McCormick, Masayuki Ochi, Zhiying Zhao, Michi-To Suzuki, Ryotaro Arita, Yun Wu, Daixiang Mou, Huibo Cao, Jiaqiang Yan, Nandini Trivedi & Adam Kaminski, Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2. Nature Materials (2016), doi:10.1038/nmat4685 [3] Yun Wu, Tai Kong, Lin-Lin Wang, D. D. Johnson, Daixiang Mou, Lunan Huang, Benjamin Schrunk, S. L. Bud'ko, P. C. Canfield, and Adam Kaminski, Asymmetric mass acquisition in LaBi: Topological semimetal candidate. Phys. Rev. B 94, 081108(R) (2016) [4] Yun Wu, Lin-Lin Wang, Eundeok Mun, D. D. Johnson, Daixiang Mou, Lunan Huang, Yongbin Lee, S. L. Bud’ko, P. C. Canfield & Adam Kaminski, Dirac node arcs in PtSn4. Nature Physics (2016), doi:10.1038/nphys3712 [Preview Abstract] |
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