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Session E45: Mott Insulators

8:00 AM–11:00 AM, Tuesday, March 6, 2018
LACC Room: 505

Sponsoring Unit: DCMP
Chair: Wenxin Ding, Kavli Institute on Theoretical Sciences, Beijing

Abstract: E45.00012 : Metallicity beyond Mott-Ioffe-Regel limit in n-doped strontium titanate

10:12 AM–10:24 AM

    Abstract  

Presenter:

Kamran Behnia
(10 Rue Vauquelin, ESPCI)

Authors:

Kamran Behnia
(10 Rue Vauquelin, ESPCI)

Xiao Lin
(10 Rue Vauquelin, ESPCI)

Willem Rischau
(10 Rue Vauquelin, ESPCI)

Benoit Fauque
(10 Rue Vauquelin, ESPCI)

Cooling oxygen-deficient strontium titanate to liquid-helium temperature leads to a decrease in its electrical resistivity by several orders of magnitude. The temperature dependence of resistivity follows a T-cubic behavior before becoming quadratic in the low-temperature limit, as expected in a Fermi liquid. Here, we show that the roughly cubic resistivity above 100K corresponds to a regime where the quasi-particle mean-free-path is shorter than the electron wave-length and the interatomic distance. These criteria define the Mott-Ioffe-Regel limit. Exceeding this limit occurs in strontium titanate well below room temperature, in contrast to other perovskytes. We argue that the T-cubic resistivity cannot be accounted for by electron-phonon scattering à la Bloch-Gruneisen and consider an alternative scheme based on Landauer transmission between individual dopants hosting polarons. We find a scaling relationship between carrier mobility, the electric permittivity and the frequency of transverse optical soft mode in this temperature range. Providing an account of this observation emerges as a challenge to theory.