Electronic spin susceptibility in metallic strontium titanate

Abstract

Metallic strontium titanate (SrTiO${}_3$) is known to have both normal-state and superconducting properties that vary strongly over a wide range of charge carrier densities. This indicates the importance of nonlinear dynamics, and has hindered the development of a clear qualitative description of the observed behaviour. A major challenge is to understand how the charge carriers themselves evolve with doping and temperature, with possible polaronic effects and evidence of an effective mass that strongly increases with temperature. Here we use ${}^{47,49}$Ti nuclear magnetic resonance (NMR) to perform a comprehensive study of the electronic spin susceptibility in the dilute metallic state of strontium titanate across the doping-temperature phase diagram. We find a temperature-dependent Knight shift that can be quantitatively understood within a non-degenerate Fermi gas model that fully takes into account the complex band structure of SrTiO${}_3$. Our data are consistent with a temperature-independent effective mass, and we show that the behavior of the spin susceptibility is universal in a wide range of temperatures and carrier concentrations. These results provide a microscopic foundation for the understanding of the properties of the unconventional low-density metallic state in strontium titanate and related materials.

8 pages, 4 figures

References in corpus (13)

• Two-dimensional superconductivity at the surfaces of KTaO3 gated with ionic liquid
• Electron-phonon interaction and charge carrier mass enhancement in SrTiO3
• Accumulation, inversion, and depletion layers in SrTiO${}_3$
• Superconductivity from energy fluctuations in dilute quantum critical polar metals
• Mesoscopic tunneling in strontium titanate
• Enhanced Critical Field of Superconductivity at an Oxide Interface
• Theory of superconductivity mediated by Rashba coupling in incipient ferroelectrics
• Superconductivity enhancement in polar metal regions of Sr${}_{0.95}$Ba${}_{0.05}$TiO${}_3$ and Sr${}_{0.985}$Ca${}_{0.015}$TiO${}_3$ revealed by the systematic Nb doping
• Theory of superconductivity in doped quantum paraelectrics
• Generalized Rashba Electron-Phonon Coupling and Superconductivity in Strontium Titanate
• A theory of criticality for quantum ferroelectric metals
• T-square dependence of the electronic thermal resistivity in metallic strontium titanate
• Phonon-Induced Collective Modes in Spin-Orbit Coupled Polar Metals