Concomitant formation of a pseudogap with the β−to−β′ structural phase transition in melt-quenched As2Te3

Abstract

${\mathrm{As}}_{2}{\mathrm{Te}}_{3}$ is a chalcogenide with many polymorphic phases. Of current interest are the $\ensuremath{\beta}$ and ${\ensuremath{\beta}}^{\ensuremath{'}}$ phases which have been investigated primarily in the context of their close relationship to the isostructural topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$. The $\ensuremath{\beta}$-to-${\ensuremath{\beta}}^{\ensuremath{'}}$ phase transition of ${\mathrm{As}}_{2}{\mathrm{Te}}_{3}$ exhibits a large anomaly in the resistivity that has remained unexplained. In this work we have measured the electronic transport properties of this phase transition in melt-quenched ${\mathrm{As}}_{2}{\mathrm{Te}}_{3}$ via dc resistivity and infrared reflectivity measurements. A sigmoidal fit has been used to describe the general behavior of the resistivity curves over a wide temperature range in order to characterize how hysteresis affects the phase transition anomaly. The optical measurements have identified the formation of a concomitant pseudogap of magnitude $\ensuremath{\approx}100\phantom{\rule{4pt}{0ex}}\mathrm{meV}$ affecting approximately $25%$ of the carriers. Charge density wave order is compatible with the formation of a partial gap as well as the observation of thermal hysteresis, suggesting it could be responsible for the $\ensuremath{\beta}\text{\ensuremath{-}}{\ensuremath{\beta}}^{\ensuremath{'}}$ transition in melt-quenched ${\mathrm{As}}_{2}{\mathrm{Te}}_{3}$.