CNR ExploRA

Articolo in rivista, 2019, ENG, 10.1088/2516-1075/ab0835

Electronic properties of candidate type-II Weyl semimetal WTe . A review perspective

P K Das1,14 , D Di Sante2, F Cilento3, C Bigi4, D Kopic5, D Soranzio5 , A Sterzi3, J A Krieger6,7,8, I Vobornik9, 9 10 6 1,11 3,5 4,9 12 2 JFujii ,TOkuda ,VNStrocov ,MBHBreese ,FParmigiani ,GRossi ,SPicozzi ,RThomale , G Sangiovanni2, R J Cava13 and G Panaccione9,14

1 Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, 117603, Singapore 2 Institut für Theoretische Physik und Astrophysik, Universität Würzburg, Am Hubland Campus Süd, Würzburg 97074, Germany 3 Elettra--Sincrotrone Trieste S.C.p.A., Strada Statale 14, km 163.5, Trieste 34149, Italy 4 Dipartimento di Fisica, Universitá di Milano, Via Celoria 16, I-20133 Milano, Italy 5 Universitá degli Studi di Trieste, Via A. Valerio 2, Trieste 34127, Italy 6 Paul Scherrer Institute, Swiss Light Source, CH-5232 Villigen, Switzerland 7 Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland 8 Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Switzerland 9 Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, in Area Science Park, S.S.14, Km 163.5, I-34149 Trieste, Italy 10 Hiroshima Synchrotron Radiation Center (HSRC), Hiroshima University, 2-313 Kagamiyama, Higashi-Hiroshima 739-0046, Japan 11 Department of Physics, National University of Singapore, 117576, Singapore 12 Consiglio Nazionale delle Ricerche (CNR-SPIN), c/o Univ. Chieti-Pescara 'G. D'Annunzio', 66100 Chieti, Italy 13 Department of Chemistry, Princeton University, Princeton, NJ 08544, United States of America

Currently, there is a flurry of research interest on materials with an unconventional electronic structure, and we have already seen significant progress in their understanding and engineering towards real-life applications. The interest erupted with the discovery of graphene and topological insulators in the previous decade. The electrons in graphene simulate massless Dirac Fermions with a linearly dispersing Dirac cone in their band structure, while in topological insulators, the electronic bands wind non-trivially in momentum space giving rise to gapless surface states and bulk bandgap. Weyl semimetals in condensed matter systems are the latest addition to this growing family of topological materials. Weyl Fermions are known in the context of high energy physics since almost the beginning of quantum mechanics. They apparently violate charge conservation rules, displaying the 'chiral anomaly', with such remarkable properties recently theoretically predicted and experimentally verified to exist as low energy quasiparticle states in certain condensed matter systems. Not only are these new materials extremely important for our fundamental understanding of quantum phenomena, but also they exhibit completely different transport phenomena. For example, massless Fermions are susceptible to scattering from non-magnetic impurities. Dirac semimetals exhibit non-saturating extremely large magnetoresistance as a consequence of their robust electronic bands being protected by time reversal symmetry. These open up whole new possibilities for materials engineering and applications including quantum computing. In this review, we recapitulate some of the outstanding properties of WTe2, namely, its non-saturating titanic magnetoresistance due to perfect electron and hole carrier balance up to a very high magnetic field observed for the very first time. It also indicative of hosting Lorentz violating type-II Weyl Fermions in its bandstructure, again first predicted candidate material to host such a remarkable phase. We primarily focus on the findings of our ARPES, spin-ARPES, and time-resolved ARPES studies complemented by first-principles calculations.

Electronic structure and magnetism of inorganic compounds Electron. Struct. 1 (2019) 014003