セミナー案内

日時
8月8日 (水), 13:30-
場所
京都大学理学部 5号館 413
講演者
Shota Kanasugi
(Condensed Matter Theory Group)
タイトル
"Spin-orbit-coupled ferroelectric superconductivity"
備考欄 (アブストラクト等)

Abstract:
Recently, the relationship between superconductivity and parity-breaking order is attracting a lot of attention from both theoretical and experimental aspect. From a theoretical point of view, Kozii and Fu proposed the odd-parity superconductivity which is induced by the fluctuation of the parity-breaking order [1]. Furthermore, several materials indicate a close relationship between superconductivity and parity-breaking order, e. g. Cd2Re2O7 [2], Sr3Rh4Sn13 [3], and MoTe2 [4]. Especially, a coexistent phase of the superconductivity and the ferroelectric (FE) order, namely FE superconducting phase, was discovered in SrTiO3 last year [5]. Since the FE order had been considered to compete with the superconducting order, this experimental result reignited a flurry of interest in the relationship between superconductivity and ferroelectricity.
Motivated by the above recent studies, we investigated the coexistent phenomena of the superconductivity and the FE order [6]. As a minimal model, we consider a quasi-two-dimensional superconductivity coupled to a polar lattice distortion. In our model, electrons and lattice are coupled via the Rashba-type antisymmetric spin-orbit coupling. We show that the FE-like order is induced by the magnetic field when the system is superconducting. This result opens a way to control the electric polarization by superconductivity. Furthermore, it is revealed that the stability of the FE superconducting state is increased in low carrier density superconductors, such as dilute superconducting SrTiO3.


Reference:
[1] V. Kozii and L. Fu, Phys. Rev. Lett. 115, 207002 (2015).
[2] J. Yamaura et al., Phys. Rev. B 95, 020102 (2017).
[3] W. C. Yu et al., Phys. Rev. Lett. 115, 207003 (2015).
[4] H. Takahashi et al., Phys. Rev. B 95, 100501 (2017).
[5] C. W. Rischau et al., Nat. Phys. 13, 643 (2017).
[6] S. Kanasugi and Y. Yanase, arXiv:1803.07279 (2018).