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arXiv · 2208.04098

Van der Waals engineering of ultrafast carrier dynamics in magnetic heterostructures

Paulina Majchrzak·Yuntian Liu·Klara Volckaert·Deepnarayan Biswas·Chakradhar Sahoo·Denny Puntel·Wibke Bronsch·Manuel Tuniz·Federico Cilento·Xing-Chen Pan·Qihang Liu·Yong P. Chen·Søren Ulstrup
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Abstract

Heterostructures composed of the intrinsic magnetic topological insulator MnBi$_2$Te$_4$ and its non-magnetic counterpart Bi$_2$Te$_3$ host distinct surface electronic band structures depending on the stacking order and exposed termination. Here, we probe the ultrafast dynamical response of MnBi$_2$Te$_4$ and MnBi$_4$Te$_7$ following near-infrared optical excitation using time- and angle-resolved photoemission spectroscopy, and disentangle surface from bulk dynamics based on density functional theory slab calculations of the surface-projected electronic structure. We gain access to the out-of-equilibrium charge carrier populations of both MnBi$_2$Te$_4$ and Bi$_2$Te$_3$ surface terminations of MnBi$_4$Te$_7$, revealing an instantaneous occupation of states associated with the Bi$_2$Te$_3$ surface layer followed by carrier extraction into the adjacent MnBi$_2$Te$_4$ layers with a laser fluence-tunable delay of up to 350 fs. The ensuing thermal relaxation processes are driven by phonon scattering with significantly slower relaxation times in the magnetic MnBi$_2$Te$_4$ septuple layers. The observed competition between interlayer charge transfer and intralayer phonon scattering demonstrates a method to control ultrafast charge transfer processes in MnBi$_2$Te$_4$-based van der Waals compounds.

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Paulina Majchrzak, Yuntian Liu, Klara Volckaert, Deepnarayan Biswas, Chakradhar Sahoo, Denny Puntel, Wibke Bronsch, Manuel Tuniz, Federico Cilento, Xing-Chen Pan, Qihang Liu, Yong P. Chen, Søren Ulstrup. 2022-08-08. Van der Waals engineering of ultrafast carrier dynamics in magnetic heterostructures. https://doi.org/10.1021/acs.nanolett.2c03075

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