Quantum diffusion regime of the charge transport in GdB6 caused by electron and lattice instability

TL;DR

This study uncovers how electron and lattice instabilities, including Gd3+ dimers and dynamic charge stripes, lead to strong charge carrier scattering in GdB6's quantum diffusion regime, using X-ray analysis and heat capacity data.

Contribution

It reveals the formation of Gd3+ dimers and dynamic charge stripes as causes of charge transport anomalies in GdB6, combining structural and thermodynamic analysis.

Findings

Identification of Gd3+ dimers with ~3.3 Å size

Detection of dynamic charge stripes along [001]

Determination of double-well potential barrier height

Abstract

Based on accurate X-ray structure analysis of GdB6 over the temperature range 85-300 K it has been shown that anomalously strong charge carrier scattering in the quantum diffusion regime of charge transport in this compound arises due to the formation of (i) dynamically coupled Gd3+ dimers of about 3.3 {\AA} in size with an energy of quasi-local oscillations ~ 7 - 8 meV and (ii) dynamic charge stripes along the [001] direction of the cubic lattice. It has been revealed that anharmonic approximation is useful when analyzing the static and dynamic components of the atomic displacement parameters of gadolinium. The barrier height of double-well potential of Gd3+ ions was determined both from low-temperature heat capacity measurements and from the electron density distribution reconstructed from X-ray data.