Heavy Nondegenerate Electrons in Doped Strontium Titanate

Room-temperature metallicity of lightly doped SrTiO_{3} is puzzling, because the combination of mobility and the effective mass would imply a mean-free path below the Mott-Ioffe-Regel limit and a scattering time shorter than the Planckian time (τ_{P}=ℏ/k_{B}T). We present a study of electric resisti...

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Autores principales:	Clément Collignon, Phillipe Bourges, Benoît Fauqué, Kamran Behnia
Formato:	article
Lenguaje:	EN
Publicado:	American Physical Society 2020
Materias:	Physics QC1-999
Acceso en línea:	https://doaj.org/article/8d587ddd1ea840588d1eb926d8733adf
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spelling	oai:doaj.org-article:8d587ddd1ea840588d1eb926d8733adf2021-12-02T13:31:08ZHeavy Nondegenerate Electrons in Doped Strontium Titanate10.1103/PhysRevX.10.0310252160-3308https://doaj.org/article/8d587ddd1ea840588d1eb926d8733adf2020-08-01T00:00:00Zhttp://doi.org/10.1103/PhysRevX.10.031025http://doi.org/10.1103/PhysRevX.10.031025https://doaj.org/toc/2160-3308Room-temperature metallicity of lightly doped SrTiO_{3} is puzzling, because the combination of mobility and the effective mass would imply a mean-free path below the Mott-Ioffe-Regel limit and a scattering time shorter than the Planckian time (τ_{P}=ℏ/k_{B}T). We present a study of electric resistivity, Seebeck coefficient, and inelastic neutron scattering extended to very high temperatures, which deepens the puzzle. Metallic resistivity persists up to 900 K and is accompanied by a large Seebeck coefficient whose magnitude (as well as its temperature and doping dependence) indicates that carriers are becoming heavier with rising temperature. Combining this with neutron scattering data, we find that between 500 and 900 K the Bohr radius and the electron wavelength become comparable to each other and twice the lattice parameter. According to our results, between 100 and 500 K, metallicity is partially driven by temperature-induced amplification of the carrier mass. We contrast this mass amplification of nondegenerate electrons with the better-known case of heavy degenerate electrons. Above 500 K, the mean-free path continues to shrink with warming in spite of becoming shorter than both the interatomic distance and the thermal wavelength of the electrons. The latter saturates to twice the lattice parameter. Available theories of polaronic quasiparticles do not provide satisfactory explanation for our observations.Clément CollignonPhillipe BourgesBenoît FauquéKamran BehniaAmerican Physical SocietyarticlePhysicsQC1-999ENPhysical Review X, Vol 10, Iss 3, p 031025 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Physics QC1-999
spellingShingle	Physics QC1-999 Clément Collignon Phillipe Bourges Benoît Fauqué Kamran Behnia Heavy Nondegenerate Electrons in Doped Strontium Titanate
description	Room-temperature metallicity of lightly doped SrTiO_{3} is puzzling, because the combination of mobility and the effective mass would imply a mean-free path below the Mott-Ioffe-Regel limit and a scattering time shorter than the Planckian time (τ_{P}=ℏ/k_{B}T). We present a study of electric resistivity, Seebeck coefficient, and inelastic neutron scattering extended to very high temperatures, which deepens the puzzle. Metallic resistivity persists up to 900 K and is accompanied by a large Seebeck coefficient whose magnitude (as well as its temperature and doping dependence) indicates that carriers are becoming heavier with rising temperature. Combining this with neutron scattering data, we find that between 500 and 900 K the Bohr radius and the electron wavelength become comparable to each other and twice the lattice parameter. According to our results, between 100 and 500 K, metallicity is partially driven by temperature-induced amplification of the carrier mass. We contrast this mass amplification of nondegenerate electrons with the better-known case of heavy degenerate electrons. Above 500 K, the mean-free path continues to shrink with warming in spite of becoming shorter than both the interatomic distance and the thermal wavelength of the electrons. The latter saturates to twice the lattice parameter. Available theories of polaronic quasiparticles do not provide satisfactory explanation for our observations.
format	article
author	Clément Collignon Phillipe Bourges Benoît Fauqué Kamran Behnia
author_facet	Clément Collignon Phillipe Bourges Benoît Fauqué Kamran Behnia
author_sort	Clément Collignon
title	Heavy Nondegenerate Electrons in Doped Strontium Titanate
title_short	Heavy Nondegenerate Electrons in Doped Strontium Titanate
title_full	Heavy Nondegenerate Electrons in Doped Strontium Titanate
title_fullStr	Heavy Nondegenerate Electrons in Doped Strontium Titanate
title_full_unstemmed	Heavy Nondegenerate Electrons in Doped Strontium Titanate
title_sort	heavy nondegenerate electrons in doped strontium titanate
publisher	American Physical Society
publishDate	2020
url	https://doaj.org/article/8d587ddd1ea840588d1eb926d8733adf
work_keys_str_mv	AT clementcollignon heavynondegenerateelectronsindopedstrontiumtitanate AT phillipebourges heavynondegenerateelectronsindopedstrontiumtitanate AT benoitfauque heavynondegenerateelectronsindopedstrontiumtitanate AT kamranbehnia heavynondegenerateelectronsindopedstrontiumtitanate
_version_	1718392866758197248

Heavy Nondegenerate Electrons in Doped Strontium Titanate

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