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Electron-Phonon Coupling and Dilute Superconductivity in SrTiO<sub>3</sub>

Invited

Abstract

The nature of superconductivity in the dilute semiconductor SrTiO3 has remained an open question for over half a century. Thin film heterostructures provide new opportunities to examine SrTiO3 superconductivity using a newly developed method for engineering band alignments at oxide interfaces to access the electronic structure of Nb-doped SrTiO3 using high-resolution tunneling spectroscopy. While we observe strong coupling to the highest-energy longitudinal optic phonon consistent with λ ~ 1, the superconducting gap is found to be in the weak-coupling limit of BCS theory, i.e. λBCS~ 0.1. This discrepancy arises in the context of an unusual anti-adiabatic condition for superconductivity in SrTiO3 (Fermi energy < Debye energy), which we find precisely bounds the superconducting dome.

This work was done in collaboration with Hyeok Yoon, Adrian Swartz, Hisashi Inoue, Yasuyuki Hikita, and Sri Raghu.

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Presenters

  • Harold Hwang

    Institute for Materials and Energy Sciences, Stanford University, Stanford University, Department of Applied Physics, Stanford University, Applied Physics, Stanford University, SIMES, SLAC, Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA, SLAC National Accelerator Lab., Physics, Stanford University, Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory

Authors

  • Harold Hwang

    Institute for Materials and Energy Sciences, Stanford University, Stanford University, Department of Applied Physics, Stanford University, Applied Physics, Stanford University, SIMES, SLAC, Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA, SLAC National Accelerator Lab., Physics, Stanford University, Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory