セミナー案内

日時
5月29日 (水), 13:30-
場所
京都大学理学部 5号館 413
講演者
Mr. Shota Kanasugi
(Condensed Matter Theory Group)
タイトル
"Multiorbital ferroelectric superconductivity in doped SrTiO3"
備考欄 (アブストラクト等)

Abstract:
A lot of exotic superconducting state emerge close to other ordered phases, such as anisotropic superconductivity in cuprates. Although previous studies have mainly focused on the superconductivity close to magnetic instability, the ferroelectric (FE) counterpart is recently receiving increased attention since such superconductivity was reported in doped SrTiO3 (STO). STO is a unique compound which exhibits both quantum paraelectricity and superconductivity. The superconducting transition temperature is enhanced in the vicinity of the FE critical point [1-3]. Moreover, recent experiments suggest the coexistence of superconductivity and ferroelectricity in doped STO [2,4]. These results imply a cooperative correlation between superconductivity and ferroelectricity against a long-held belief that they should be incompatible.
In this talk, we present that STO can be a platform of the FE superconductivity which is characterized by a FE transition in the superconducting state [5]. By analyzing a multiorbital model for t2g electrons, we investigate the interplay of superconductivity and FE order in bulk STO. It is shown that the FE superconductivity is realized through two different mechanisms which rely on the intrinsic spin-orbit coupling [6]. First, the FE superconducting state is stabilized by the Lifshitz transition in dilute carrier density regimes [7]. Second, the FE superconductisng state is stabilized under a Zeeman magnetic field. Furthermore, we show that the FE superconductivity is strongly affected by the multiorbital effect, and thus a topological Weyl superconducting state is realized in the FE superconducting STO.

Reference:
[1] A. Stucky et al., Sci. Rep. 6, 37582 (2016).
[2] C. W. Rischau et al., Nat. Phys. 13, 643 (2017).
[3] Y. Tomioka et al., Nat. Commun. 10, 738 (2019).
[4] K. Ahadi et al., Sci. Adv. 5, eaaw0120 (2019).
[5] S. Kanasugi and Y. Yanase, arXiv: 1904.11113 (2019).
[6] S. Kanasugi and Y. Yanase, Phys. Rev. B 98, 024521 (2018).
[7] E. Cappelluti, C. Grimaldi, and F. Marsiglio, Phys. Rev. Lett. 98, 167002 (2007).