セミナー案内

日時
10月17日 (水), 13:30-
場所
京都大学理学部 5号館 413
講演者
Mr. Shuntaro Sumita
(Condensed Matter Theory Group)
タイトル
"Classification of topological crystalline superconducting nodes on high-symmetry line"
備考欄 (アブストラクト等)

Abstract:
Recent exact classification of a superconducting gap have elucidated unconventional gap structures [1-8], which have not been predicted by the classification of order parameter based on the point group [9]. One of the important previous results is that all symmetry-protected line nodes on mirror- or glide-invariant planes in the Brillouin zone are characterized by a nontrivial topological number [6, 7]. Another discovery is the novel gap structures depending on the angular momentum of the normal state j_z on threefold and sixfold rotational-symmetric lines [1, 3, 8]. Stimulated by these facts, we classify all crystal symmetry-protected nodes (including such j_z-dependent nodes) on high-symmetry n-fold (n = 2, 3, 4, and 6) axes, by using the combination of group theory and K-theory [10]. As a result, it is shown that the classification by group theory completely corresponds with the topological classification. We also discuss superconducting gap structures in SrPtAs, CeCoIn_5, UPt_3, and UCoGe.

Reference:
[1] V. G. Yarzhemsky and E. N. Murav'ev, J. Phys.: Condens. Matter 4, 3525 (1992).
[2] M. R. Norman, Phys. Rev. B 52, 15093 (1995).
[3] V. G. Yarzhemsky, Phys. Status Solidi B 209, 101 (1998).
[4] T. Micklitz and M. R. Norman, Phys. Rev. B 80, 100506 (2009).
[5] T. Nomoto and H. Ikeda, J. Phys. Soc. Jpn. 86, 023703 (2017).
[6] T. Micklitz and M. R. Norman, Phys. Rev. Lett. 118, 207001 (2017).
[7] S. Kobayashi, S. Sumita, Y. Yanase, and M. Sato, Phys. Rev. B 97, 180504 (2018).
[8] S. Sumita and Y. Yanase, Phys. Rev. B 97, 134512 (2018).
[9] M. Sigrist and K. Ueda, Rev. Mod. Phys. 63, 239 (1991).
[10] K. Shiozaki, M. Sato, and K. Gomi, arXiv:1802.06694.