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arXiv · 2405.11737

Nonequilibrium carrier and phonon dynamics in the ferrimagnetic semiconductor Mn$_3$Si$_2$Te$_6$

Y. Yang·X. T. Chen·Z. L. Li·J. B. Pan·F. Jing·S. S. Zhang·X. B. Wang·J. L. Luo
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Abstract

We investigate the ultrafast carrier and phonon dynamics in the ferrimagnetic semiconductor Mn$_3$Si$_2$Te$_6$ using time-resolved optical pump-probe spectroscopy. Our results reveal that the electron-phonon thermalization process with a subpicosecond timescale is prolonged by the hot-phonon bottleneck effect. We identify the subsequent relaxation processes associated with two non-radiative recombination mechanisms, i.e., phonon-assisted electron-hole recombination and defect-related Shockley-Read-Hall recombination. Temperature-dependent measurements indicate that all three relaxation components show large variation around 175 and 78 K, which is related to the initiation of spin fluctuation and ferrimagnetic order in Mn$_3$Si$_2$Te$_6$. In addition, two pronounced coherent optical phonons are observed, in which the phonon with a frequency of 3.7 THz is attributed to the $A_{1g}$ mode of Te precipitates. Applying the strain pulse propagation model to the coherent acoustic phonons yields a penetration depth of 506 nm and a sound speed of 2.42 km/s in Mn$_3$Si$_2$Te$_6$. Our results develop understanding of the nonequilibrium properties of the ferrimagnetic semiconductor Mn$_3$Si$_2$Te$_6$, and also shed light on its potential applications in optoelectronic and spintronic devices.

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Y. Yang, X. T. Chen, Z. L. Li, J. B. Pan, F. Jing, S. S. Zhang, X. B. Wang, J. L. Luo. 2024-05-20. Nonequilibrium carrier and phonon dynamics in the ferrimagnetic semiconductor Mn$_3$Si$_2$Te$_6$. https://doi.org/10.1103/physrevb.109.174309

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