Superconductivity of Ferroelectric SrTiO3 Films - Susanne Stemmer, University of California

10.06.2021 16:00 – 16:45

Superconductivity of Ferroelectric SrTiO3 Films
Susanne Stemmer
Materials Department, University of California, Santa Barbara, CA 93106-5050, USA

Superconductivity in electron-doped SrTiO3 was discovered almost 60 years ago. Already early on it was recognized that certain aspects of its superconductivity, including a Fermi energy that is much lower than the Debye temperature, challenge standard BCS theory. Moreover, SrTiO3 can also be a polar superconductor that undergoes a ferroelectric transition prior to becoming superconducting. Spin-orbit coupling becomes important in superconductors with broken inversion symmetry, which can lead to unconventional superconductivity. This talk will focus on our recent studies of the ferroelectric and superconducting states of strained SrTiO3 films grown by molecular beam epitaxy. We show that the ferroelectric transition is better described as an order-disorder transition and that local polar order persists to temperatures far above the ferroelectric transition. We discuss the mechanisms by which free carriers and dopants act to suppress the ferroelectric transition. We also discuss our recent insights into the nature of the superconducting state, including its enhanced superconducting transition temperature, obtained via non-reciprocal transport measurements and other experiments.

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