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T-square resistivity in SrTiO3 and other dilute metals

Kamran Behnia

Parc Club bât 23-25, salle 215 1er étage

Doping a semiconductor will eventually lead to the emergence of a metallic ground state. In contrast to silicon and germanium, infinitesimal doping transforms strontium titanate (SrTiO3) to a metal. Thanks to its long Bohr radius, the dilute metallic state hosts extremely mobile carriers in a shallow Fermi sea over a seafloor carved by distant dopants [1], leading to the observation of quantum oscillations at moderate magnetic fields[2].

In Fermi liquids, electron-electron scattering generates a distinct contribution to electrical resistivity following quadratic temperature dependence. In the case of heavy-electron metals, A, the prefactor of this T2 term becomes orders of magnitude larger than in ordinary metals and scales with the square of the electronic specific heat. This is known as the Kadowaki-Woods plot [3]. We have found that in SrTiO3, A can be tuned over four orders of magnitude. Mysteriously, the behavior persists in the single-band and dilute limit. This happens despite the absence of two known mechanisms for T2 behavior, distinct electron reservoirs and Umklapp processes [4]. We show that according to available data, the magnitude of A in many dilute metals is loosely linked to the amplitude of their Fermi energy.

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