Layered tin selenide (SnSe) has recently emerged as a high-performance thermoelectric material with the current record for the figure of merit (ZT) observed in the high-temperature Cmcm phase. So far, access to the Cmcm phase has been mainly obtained via thermal equilibrium methods based on sample heating or application of external pressure, thus restricting the current understanding only to ground-state conditions. Here, we investigate the ultrafast carrier and phononic dynamics in SnSe. Our results demonstrate that optical excitations can transiently switch the point-group symmetry of the crystal from Pnma to Cmcm at room temperature in a few hundreds of femtoseconds with an ultralow threshold for the excitation carrier density. This nonequilibrium Cmcm phase is found to be driven by the displacive excitation of coherent Ag phonons and, given the absence of low-energy thermal phonons, exists in SnSe with the status of 'cold lattice with hot carriers'. Our findings provide an important insight for understanding the nonequilibrium thermoelectric properties of SnSe.

Han, Y., Yu, J., Zhang, H., Xu, F., Peng, K., Zhou, X., et al. (2022). Photoinduced Ultrafast Symmetry Switch in SnSe. THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 13(2), 442-448 [10.1021/acs.jpclett.1c03704].

Photoinduced Ultrafast Symmetry Switch in SnSe

Vanacore G. M.;
2022

Abstract

Layered tin selenide (SnSe) has recently emerged as a high-performance thermoelectric material with the current record for the figure of merit (ZT) observed in the high-temperature Cmcm phase. So far, access to the Cmcm phase has been mainly obtained via thermal equilibrium methods based on sample heating or application of external pressure, thus restricting the current understanding only to ground-state conditions. Here, we investigate the ultrafast carrier and phononic dynamics in SnSe. Our results demonstrate that optical excitations can transiently switch the point-group symmetry of the crystal from Pnma to Cmcm at room temperature in a few hundreds of femtoseconds with an ultralow threshold for the excitation carrier density. This nonequilibrium Cmcm phase is found to be driven by the displacive excitation of coherent Ag phonons and, given the absence of low-energy thermal phonons, exists in SnSe with the status of 'cold lattice with hot carriers'. Our findings provide an important insight for understanding the nonequilibrium thermoelectric properties of SnSe.
Articolo in rivista - Articolo scientifico
SnSe; ultrafast pump-probe; phase transition
English
442
448
7
Han, Y., Yu, J., Zhang, H., Xu, F., Peng, K., Zhou, X., et al. (2022). Photoinduced Ultrafast Symmetry Switch in SnSe. THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, 13(2), 442-448 [10.1021/acs.jpclett.1c03704].
Han, Y; Yu, J; Zhang, H; Xu, F; Peng, K; Zhou, X; Qiao, L; Misochko, O; Nakamura, K; Vanacore, G; Hu, J
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/394348
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