Fermi surface of the most dilute superconductor

Abstract

The origin of superconductivity in bulk SrTiO${}_3$ is a mystery, since the non-monotonous 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 $5.5\times 10^{17}c{m}^{-3}$, the system has both a sharp Fermi surface and a superconducting ground state. The most dilute superconductor currently known has therefore 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. 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.

Final version

References in corpus (6)

• Electric Field Control of the LaAlO${}_3$/SrTiO${}_3$ Interface Ground State
• On the thermoelectricity of correlated electrons in the zero-temperature limit
• Electron-phonon interaction and charge carrier mass enhancement in SrTiO3
• The Nernst effect and the boundaries of the Fermi liquid picture
• Oscillating Nernst-Ettingshausen effect in Bismuth across the quantum limit
• Specific heat and electronic states of superconducting boron-doped silicon carbide