Abstract
The origin of superconductivity in bulk SrTiO3 is a mystery since the nonmonotonous variation of the critical transition with carrier concentration defies the expectations of the crudest version of the BCS theory. Here, employing the Nernst effect, an extremely sensitive probe of tiny bulk Fermi surfaces, we show that, down to concentrations as low as 5.5×1017 cm−3, the system has both a sharp Fermi surface and a superconducting ground state. The most dilute superconductor currently known therefore has a metallic normal state with a Fermi energy as little as 1.1 meV on top of a band gap as large as 3 eV. The occurrence of a superconducting instability in an extremely small, single-component, and barely anisotropic Fermi surface implies strong constraints for the identification of the pairing mechanism.Received 5 December 2012DOI:https://doi.org/10.1103/PhysRevX.3.021002This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical Society
Highlights
SrTiO3 is a large-gap transparent insulator, which, upon the introduction of n-type carriers, undergoes a superconducting transition below 1 K
The origin of superconductivity in bulk SrTiO3 is a mystery since the nonmonotonous variation of the critical transition with carrier concentration defies the expectations of the crudest version of the BCS theory
Our work addresses two hitherto unanswered questions. (i) Is there a threshold in carrier concentration for the emergence of superconductivity? (ii) Does the normal state of such a low-density superconductor have a well-defined Fermi surface, or is it an impurity-band metal? We provide answers to these questions by a study of the low-temperature Nernst effect in both oxygenreduced and Nb-doped SrTiO3 across a wide (i.e., 3-orders-of-magnitude) window of carrier density
Summary
SrTiO3 is a large-gap transparent insulator, which, upon the introduction of n-type carriers, undergoes a superconducting transition below 1 K. We provide answers to these questions by a study of the low-temperature Nernst effect (a very sensitive probe of tiny Fermi surfaces [21,22,23]) in both oxygenreduced and Nb-doped SrTiO3 across a wide (i.e., 3-orders-of-magnitude) window of carrier density. We find that superconductivity persists down to a carrier concentration that is significantly lower than what was previously believed This result firmly establishes n-doped SrTiO3 as the most dilute known superconductor with a carrier density as low as 5:5 Â 1017 cmÀ3, which corresponds to the removal of one oxygen atom out of 105. At this carrier concentration, giant Nernst quantum oscillations with a single frequency are observed. Emerges from this study as a candidate for unconventional superconductivity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
