Gapless topological superconductivity in two-dimensional quasicrystals

Date

Jan 29, 2025

Time

3:00 PM - 4:00 PM

Speaker

Dr. Ryo Okugawa

Affiliation

Tohyama Lab, Tokyo University of Science

Language

en

Main Topic

Materialien

Host

Grit Rötzer

Description

Quasicrystals (QCs) are aperiodic materials with a long-range order. Due to the absence of the translational symmetry, a momentum-space picture cannot be directly applied to understand superconductivity in QCs. Nevertheless, various topological superconducting phases in QCs have been theoretically suggested beyond the conventional framework of topological band theory [3,4]. Interestingly, some quasicrystalline systems, including Ammann-Beenker QCs, exhibit a flat band despite their lack of periodicity. Therefore, this distinguishes QCs from a periodic crystals and disordered systems, making them a unique platform for exploring nontrivial superconductivity. In this talk, we discuss superconductivity with on-site pairing in two-dimensional Ammann-Beenker quasicrysals under magnetic field. We show that gapless superconductivity can emerge under strong magnetic field, and that the gapless spectrum stems from broken translational symmetry and flat-band states [5]. Furthermore, we demonstrate that the gapless superconductor can become topologically nontrivial in the presence of Rashba spin-orbit coupling. The gapless topological superconducting phase can be characterized by a topological invariant given by a spectral localizer. References [1] I. C. Fulga, D. I. Pikulin, and T. A. Loring, Phys. Rev. Lett. 116, 257002 (2016). [2] M. Hori, R. Okugawa, K. Tanaka, and T. Tohyama, Phys. Rev. Res. 6, 033088 (2024). [3] K. Saito, M. Hori, R. OKugawa, K. Tanaka, and T. Tohyama, arXiv.2410.01236.

Links

• Seminars at the IFW

Last modified: Jan 29, 2025, 7:39:36 AM