Weyl and Dirac semimetals and beyond– prediction, synthesis and characterization of new semimetals

• Applicants: Saicharan Aswartham, Ph.D.; Professor Dr. Bernd Büchner; Dr. Dmitri Efremov
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405940956

• Final Report Year: 2024

Final Report Abstract

Topological materials, in particular Dirac and Weyl semimetals, represent an emerging field of quantum materials. Despite significant theoretical progress, experimental progress has been less advanced. The main goal of this project is to bridge the gap between theoretical predictions and our understanding of the physical properties of real materials. Our research focuses on the study of two particularly interesting families of Weyl semimetals: TaTMTe 4 (where TM = Ir, Rh, Ru) and PtBi2. The most interesting findings within the project are the observation of superconductivity arising from the topological surface states in a Weyl semimetal PtBi2 while the bulk remains in the normal state, and the discovery of the switching effect between high and low resistive states in point contacts in Weyl semimetals. The new effects discovered during the project are very promising and may be of interest for the next generation of electronics.

Publications

• Yanson point-contact spectroscopy of Weyl semimetal WTe 2. 2D Materials, 6(4), 045012.
  Naidyuk, Yu G.; Bashlakov, D. L.; Kvitnitskaya, O. E.; Aswartham, S.; Morozov, I. V.; Chernyavskii, I. O.; Shipunov, G.; Fuchs, G.; Drechsler, S.-L.; Hühne, R.; Nielsch, K.; Büchner, B. & Efremov, D. V.
  
• Disorder-induced coupling of Weyl nodes in WTe2. Physical Review Research, 2(3).
  Sykora, Steffen; Schoop, Johannes; Graf, Lukas; Shipunov, Grigory; Morozov, Igor V.; Aswartham, Saicharan; Büchner, Bernd; Hess, Christian; Giraud, Romain & Dufouleur, Joseph
  
• Incommensurate magnet iron monophosphide FeP: Crystal growth and characterization. Physical Review Materials, 4(8).
  Chernyavskii, I. O.; Nikitin, S. E.; Onykiienko, Y. A.; Inosov, D. S.; Stahl, Q.; Geck, J.; Hong, X. C.; Hess, C.; Gass, S.; Wolter, A. U. B.; Wolf, D.; Lubk, A.; Efremov, D. V.; Yokaichiya, F.; Aswartham, S.; Büchner, B. & Morozov, I. V.
  
• Polymorphic PtBi2 : Growth, structure, and superconducting properties. Physical Review Materials, 4(12).
  Shipunov, G.; Kovalchuk, I.; Piening, B. R.; Labracherie, V.; Veyrat, A.; Wolf, D.; Lubk, A.; Subakti, S.; Giraud, R.; Dufouleur, J.; Shokri, S.; Caglieris, F.; Hess, C.; Efremov, D. V.; Büchner, B. & Aswartham, S.
  
• Separate tuning of nematicity and spin fluctuations to unravel the origin of superconductivity in FeSe. npj Quantum Materials, 5(1).
  Baek, Seung-Ho; Ok, Jong Mok; Kim, Jun Sung; Aswartham, Saicharan; Morozov, Igor; Chareev, Dmitriy; Urata, Takahiro; Tanigaki, Katsumi; Tanabe, Yoichi; Büchner, Bernd & Efremov, Dmitri V.
  
• Layered van der Waals Topological Metals of TaTMTe4 (TM = Ir, Rh, Ru) Family. The Journal of Physical Chemistry Letters, 12(28), 6730-6735.
  Shipunov, G.; Piening, B. R.; Wuttke, C.; Romanova, T. A.; Sadakov, A. V.; Sobolevskiy, O. A.; Guzovsky, E. Yu.; Usoltsev, A. S.; Pudalov, V. M.; Efremov, D. V.; Subakti, S.; Wolf, D.; Lubk, A.; Büchner, B. & Aswartham, S.
  
• Switchable domains in point contacts based on transition metal tellurides. Physical Review Materials, 5(8).
  Naidyuk, Yu. G.; Bashlakov, D. L.; Kvitnitskaya, O. E.; Piening, B. R.; Shipunov, G.; Efremov, D. V.; Aswartham, S. & Büchner, B.
  
• Absence of nematic instability in LiFeAs. Physical Review B, 106(5).
  Wissmann, Michael; Caglieris, Federico; Hong, Xiaochen; Aswartham, Saicharan; Vorobyova, Anna; Morozov, Igor; Büchner, Bernd & Hess, Christian
  
• Electron-phonon interaction and point contact enhanced superconductivity in trigonal PtBi2. Low Temperature Physics, 48(10), 747-754.
  Bashlakov, D. L.; Kvitnitskaya, O. E.; Shipunov, G.; Aswartham, S.; Feya, O. D.; Efremov, D. V.; Büchner, B. & Naidyuk, Yu. G.
  
• Semiclassical transport with Berry curvature: Chambers formula and applications to systems with Fermi surface topological transitions. Physical Review B, 105(15).
  Kokkinis, Emmanouil K.; Goldstein, Garry; Efremov, Dmitri V. & Betouras, Joseph J.
  
• Crystal growth, characterization and electronic band structure of TiSeS. Physical Review Materials, 7(3).
  Shemerliuk, Y.; Kuibarov, A.; Feia, O.; Behnami, M.; Reichlova, H.; Suvorov, O.; Selter, S.; Efremov, D. V.; Borisenko, S.; Büchner, B. & Aswartham, S.
  
• Fate of density waves in the presence of a higher-order van Hove singularity. Physical Review Research, 5(4).
  Zervou, Alkistis; Efremov, Dmitry V. & Betouras, Joseph J.
  
• Evidence of superconducting Fermi arcs. Nature, 626(7998), 294-299.
  Kuibarov, Andrii; Suvorov, Oleksandr; Vocaturo, Riccardo; Fedorov, Alexander; Lou, Rui; Merkwitz, Luise; Voroshnin, Vladimir; Facio, Jorge I.; Koepernik, Klaus; Yaresko, Alexander; Shipunov, Grigory; Aswartham, Saicharan; Brink, Jeroen van den; Büchner, Bernd & Borisenko, Sergey