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Journal Articles Proceedings of the National Academy of Sciences of the United States of America Year : 2022

Phonon drag thermal Hall effect in metallic strontium titanate

Abstract

SrTiO 3 , a quantum paralectric, displays a detectable phonon thermal Hall effect (THE). Here, we show that the amplitude of the THE is extremely sensitive to stoichiometry. It drastically decreases upon substitution of a tiny fraction of Sr atoms with Ca, which stabilizes the ferroelectric order. It drastically increases by an even lower density of oxygen vacancies, which turn the system to a dilute metal. The enhancement in the metallic state exceeds by far the sum of the electronic and the phononic contributions. We explain this observation as an outcome of three features: 1) Heat is mostly transported by phonons; 2) the electronic Hall angle is extremely large; and 3) there is substantial momentum exchange between electrons and phonons. Starting from Herring’s picture of phonon drag, we arrive to a quantitative account of the enhanced THE. Thus, phonon drag, hitherto detected as an amplifier of thermoelectric coefficients, can generate a purely thermal transverse response in a dilute metal with a large Hall angle. Our results reveal a hitherto-unknown consequence of momentum-conserving collisions between electrons and phonons.
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Dates and versions

hal-03866348 , version 1 (22-11-2022)

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Shan Jiang, Xiaokang Li, Benoît Fauqué, Kamran Behnia. Phonon drag thermal Hall effect in metallic strontium titanate. Proceedings of the National Academy of Sciences of the United States of America, 2022, 119 (35), ⟨10.1073/pnas.2201975119⟩. ⟨hal-03866348⟩
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