Electronic and vibrational properties of low-dimensional perovskites Sr$_{1-y}$La$_y$NbO$_{3.5-x}$

TL;DR

This study investigates the electronic and vibrational properties of low-dimensional perovskites Sr$_{1-y}$La$_y$NbO$_{3.5-x}$ using advanced spectroscopic techniques, revealing diverse behaviors influenced by composition and structure, including metallicity and insulating states.

Contribution

It provides new insights into how oxygen and La content affect the electronic phases and electron-phonon interactions in low-dimensional perovskites.

Findings

Small energy gaps suggest Peierls instability in some compositions.

Metallic behavior is suppressed by structural differences despite similar carrier densities.

Electron-phonon interactions are significant in determining electronic properties.

Abstract

By angle-resolved photoemission spectroscopy and polarization-dependent infrared reflectivity measurements the electronic and vibrational properties of low-dimensional perovskites Sr$_{1-y}$La$_y$NbO$_{3.5-x}$ were studied along different crystal directions. The electronic behavior strongly depends on the oxygen and La content, including quasi-one-dimensional metallic and ferroelectric insulating behavior. An extremely small energy gap at the Fermi level is found for SrNbO$_{3.41}$ and SrNbO$_{3.45}$ along the conducting direction at low temperature, suggestive for a Peierls-type instability. Despite the similar nominal carrier density, for Sr$_{0.8}$La$_{0.2}$NbO$_{3.50}$ the quasi-one-dimensional metallic character is suppressed and no gap opening is observed, which can be explained by differences in the crystal structure. Electron-phonon interaction appears to play an important role in this series of compounds.