High Temperature Charge Transport In Strontium Titanate*

Strontium titanate quickly becomes metallic upon doping, but while the fermiology of this metallic phase is well understood its transport properties remain elusive [1].
At low temperature, even though the scattering mechanism is not known, the resistivity exhibits a T² behavior typical of Fermi liquids [1]. With increasing temperature, resistivity rapidly grows and follows an unusual T³ power law [1,2]. At room-temperature, the magnitude of resistivity combined with the effective mass, m*, obtained from quantum oscillations, implies strikingly shorts mean-free-path and scattering time. The Mott-Ioffe-Regel limit is exceeded, and the scattering time decreases faster than the planckian time (τ_P= h/2πk_BT). Nevertheless, the resistivity does not show any sign of saturation.
In this talk, we present new charge transport data extended up to 850 K to follow the fate of this enigmatic metallicity at high temperatures. The system continues to display a metallic behavior without saturation in resistivity and the apparent scattering time (assuming a temperature-independent m*) becomes 10 times lower than τ_P.

[1] Collignon et al. arXiv:1804.07067
[2] X. Lin et al. npj Quantum Materials 2, 41 (2017)