28 August 2022 to 2 September 2022
Science and Technology Campus, University of Parma
Europe/Rome timezone
The Open Access Conference Proceedings is Now Available!

Unconventional superconductivity in topological ruthenium silicides with Kramers and hourglass fermions

P-MON-6
29 Aug 2022, 17:20
1h 40m
Science and Technology Campus, University of Parma

Science and Technology Campus, University of Parma

University of Parma, Italy
Poster Strongly correlated electron systems Posters

Speaker

T. Shiroka (Laboratorium für Festkörperphysik, ETHZ)

Description

The convergence of two major research strands in modern condensed-matter physics: topological materials and unconventional superconductivity, constitutes a new field of study. Topological materials with Kramers or hourglass fermions represent a special subclass, recently realized in materials lacking inversion symmetry or with a nonsymmorphic space group. At the same time, there is a surge of interest in identifying time-reversal symmetry (TRS) breaking (a key feature of unconventional superconductivity) in this class of materials, as a new routine way to realize topological superconductivity.

By using the muon-spin rotation and relaxation technique, backed by detailed theoretical analyses, we show that TRuSi (T = Ti, Nb, Hf, and Ta) noncentrosymmetric materials represent a family of compounds encompassing all the above unique properties [1]. Their bulk normal states behave as three-dimensional Kramers nodal-line semimetals, characterized by a fairly large antisymmetric spin-orbit coupling and by glide-reflection-protected hourglass-like fermions. We also identify surface states near the Fermi level of TRuSi materials More interestingly, NbRuSi and TaRuSi undergo a superconducting transition, which spontaneously breaks TRS below $T_c$, while surprisingly showing a fully-gapped superconducting ground state. This superconducting ground state is consistent with a unitary (s + ip) pairing, i.e., with a mixture of spin-singlet and spin-triplet pairings. As such, the TRuSi family provides an ideal platform for investigating the rich interplay between the exotic properties of Kramers nodal-line/hourglass fermions and unconventional superconductivity.

[1] T. Shang, J. Z. Zhao, et al., and T. Shiroka, submitted to Sci. Adv. (2022).

Primary authors

T. Shiroka (Laboratorium für Festkörperphysik, ETHZ) J. Z. Zhao (Co-Innovation Center for New Energetic Materials, Southwest University of Science and Technology,) L.-H. Hu (Department of Physics and Astronomy, University of Tennessee) J. Z. Ma (Department of Physics, City University of Hong Kong) D. J. Gawryluk (Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut) X. Y. Zhu (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University) H. Zhang (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University) Z. X. Zhen (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University) B. C. Yu (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University) Y. Xu (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University) Q. F. Zhan (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University) E. Pomjakushina (Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut) M. Shi (Swiss Light Source, Paul Scherrer Institut) T. Shang (Key Laboratory of Polar Materials and Devices (MOE), School of Physics and Electronic Science, East China Normal University)

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