Structural Inhomogeneity in Oxide Superconductors

Who: Martin Greven, University of Minnesota
When: 
Wednesday, December 8, 2021 - 4:00pm
Where: 
Zoom

Abstract: Superconductivity has been a major research topic for more than a century, yet in many important materials this macroscopic quantum phenomenon remains poorly understood. We have uncovered that superconductivity emerges in an unusual, yet remarkably universal manner upon cooling in three well-known families of complex oxides – strontium titanate, strontium ruthenate, and the cuprates – for which the origin of superconductivity is thought to differ [1]. This breakthrough was enabled by nonlinear magnetic response measurements, an innovative experimental approach that is uniquely sensitive to superconducting fluctuations. We find that the diamagnetic response above the bulk critical temperature Tc exhibits unusual exponential temperature dependence, with a characteristic temperature scale that differs from Tc. This scale correlates with the sensitivity of Tc to local stress, and it is influenced by intentionally induced structural disorder. Using diffuse neutron and X-ray scattering, we recently found further evidence that the universal electronic behavior is caused by intrinsic structural inhomogeneity that must be inherent to the oxides’ perovskite-based crystal structures [2]. The prevalence of such inhomogeneity has far-reaching implications for the interpretation of electronic properties of perovskites in general, including thin films and heterostructures. In the case of the cuprates, this inherent inhomogeneity constitutes a pivotal part of a robust phenomenological model that comprehensively captures hitherto elusive properties of the normal and superconducting states [3]. In the case of strontium titanate, these insights motivated a systematic study of plastically-deformed crystals that led to the discovery of remarkable superconductivity and ferroelectricity enhancements [4].

[1] D. Pelc et al., Nat. Commun. 10, 2729 (2019)
[2] D. Pelc et al., arXiv:2103.05482
[3] D. Pelc et al., Sci. Adv. 5, eaau4538 (2019); Phys. Rev. B 102, 075114 (2020)
[4] S. Hameed et al., Nat. Mater. (2021) (https://doi.org/10.1038/s41563-021-01102-3)

 

Biographical Info for Martin Greven:

Affiliations

Education

  • Ph.D., Massachusetts Institute of Technology, 1995
  • Vordiplom, Universität Heidelberg (Heidelberg University), 1988

Professional Background

  • Distinguished McKnight University Professor, 2018-present
  • Director, University of Minnesota Center for Quantum Materials, 2016-present
  • Professor, School of Physics and Astronomy, University of Minnesota, 2011-present
  • Associate Professor, School of Physics and Astronomy, University of Minnesota, 2009-2011
  • Assistant Professor, Applied Physics and Photon Science, Stanford University, 1998-2009
  • Post-doctoral Research Associate, Massachusetts Institute of Technology, 1995-1997

Scientific & Professional Societies

  • Fellow, American Physical Society
  • Fellow, American Association for the Advancement of Science
  • Fellow, Neutron Scattering Society of America