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  4. Oxidation States, Thouless' Pumps, and Nontrivial Ionic Transport in Nonstoichiometric Electrolytes
 
research article

Oxidation States, Thouless' Pumps, and Nontrivial Ionic Transport in Nonstoichiometric Electrolytes

Pegolo, Paolo
•
Grasselli, Federico  
•
Baroni, Stefano
November 12, 2020
Physical Review X

Thouless' quantization of adiabatic particle transport permits one to associate an integer topological charge with each atom of an electronically gapped material. If these charges are additive and independent of atomic positions, they provide a rigorous definition of atomic oxidation states and atoms can be identified as integer-charge carriers in ionic conductors. Whenever these conditions are met, charge transport is necessarily convective; i.e., it cannot occur without substantial ionic flow, a transport regime that we dub trivial. We show that the topological requirements that allow these conditions to be broken are the same that would determine a Thouless' pump mechanism if the system were subject to a suitably defined time-periodic Hamiltonian. The occurrence of these requirements determines a nontrivial transport regime whereby charge can flow without any ionic convection, even in electronic insulators. These results are first demonstrated with a couple of simple molecular models that display a quantum-pump mechanism upon introduction of a fictitious time dependence of the atomic positions along a closed loop in configuration space. We finally examine the impact of our findings on the transport properties of nonstoichiometric alkali-halide melts, where the same topological conditions that would induce a quantum-pump mechanism along certain closed loops in configuration space also determine a nontrivial transport regime such that most of the total charge current results to be uncorrelated from the ionic ones.

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Type
research article
DOI
10.1103/PhysRevX.10.041031
Web of Science ID

WOS:000588590500001

Author(s)
Pegolo, Paolo
Grasselli, Federico  
Baroni, Stefano
Date Issued

2020-11-12

Published in
Physical Review X
Volume

10

Issue

4

Article Number

041031

Subjects

Physics, Multidisciplinary

•

Physics

•

electrical-conductivity

•

gauge-invariance

•

transition

•

metals

•

localization

•

quantization

•

polarization

•

wannier90

•

chemistry

•

dynamics

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
COSMO  
Available on Infoscience
November 25, 2020
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/173626
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