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SUMMARY:Unconventional superconductivity in topological ruthenium silicide
 s  with Kramers and hourglass fermions
DTSTART;VALUE=DATE-TIME:20220829T164000Z
DTEND;VALUE=DATE-TIME:20220829T170000Z
DTSTAMP;VALUE=DATE-TIME:20220826T110631Z
UID:indico-contribution-3760@indico.stfc.ac.uk
DESCRIPTION:Speakers: T. Shiroka (Laboratorium für Festkörperphysik\, ET
 HZ)\nThe convergence of two major research strands in modern condensed-mat
 ter physics: topological materials and unconventional superconductivity\, 
 constitutes a new field of study. Topological materials with Kramers or ho
 urglass fermions represent a special subclass\, recently realized in mater
 ials lacking inversion symmetry or with a nonsymmorphic space group. At th
 e same time\, there is a surge of interest in identifying time-reversal sy
 mmetry (TRS) breaking (a key feature of unconventional superconductivity) 
 in this class of materials\, as a new routine way to realize topological s
 uperconductivity. \n\nBy using the muon-spin rotation and relaxation techn
 ique\, 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 no
 rmal states behave as three-dimensional Kramers nodal-line semimetals\, ch
 aracterized by a fairly large antisymmetric spin-orbit coupling and by gli
 de-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 bre
 aks TRS below $T_c$\, while surprisingly showing a fully-gapped supercondu
 cting 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 platfo
 rm for investigating the rich interplay between the exotic properties of K
 ramers nodal-line/hourglass fermions and unconventional superconductivity.
 \n\n[1] T. Shang\, J. Z. Zhao\, et al.\, and T. Shiroka\, submitted to *Sc
 i. Adv.* (2022).\n\nhttps://indico.stfc.ac.uk/event/53/contributions/3760/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3760/
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