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