Direct observation of multiple conduction-band minima in high-performance thermoelectric SnSe

TL;DR

This study uses time- and angle-resolved photoemission spectroscopy to observe multiple conduction-band minima in SnSe, providing insights into its high thermoelectric performance and potential for anisotropic thermoelectric applications.

Contribution

First direct observation of multiple conduction-band minima in SnSe using advanced photoemission spectroscopy techniques.

Findings

Conduction band minima are populated 90-550 fs after photoexcitation.

Observed conduction bands match theoretical band structure calculations.

Multiple conduction minima imply potential for high, anisotropic thermoelectric performance.

Abstract

We report time- and angle-resolved photoemission spectroscopy on SnSe which currently attracts great interest due to its extremely high thermoelectric performance. Laser-assisted photoemission signals are observed within $\pm$20 fs of the pump pulse arrival. Around 30-50 fs after the photoexcitation, the conduction band minima are not populated by the photoexcited electrons while the valence bands are considerably broadened. In going from 90 fs to 550 fs after the photoexcitation, the photoexcited carriers are decayed into the multiple conduction band minima. The observed conduction bands are consistent with the band structure calculations. The multiple conduction minima suggest possibility of high and anisotropic thermoelectric performance of n-type SnSe single crystal if it is realized.