Van der Waals Engineering of Ultrafast Carrier Dynamics in Magnetic Heterostructures

Paulina Ewa 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*

*Corresponding author for this work

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


Heterostructures composed of the intrinsic magnetic topological insulator MnBi2Te4 and its nonmagnetic counterpart Bi2Te3 host distinct surface electronic band structures depending on the stacking order and exposed termination. Here, we probe the ultrafast dynamical response of MnBi2Te4 and MnBi4Te7 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 MnBi2Te4 and Bi2Te3 surface terminations of MnBi4Te7, revealing an instantaneous occupation of states associated with the Bi2Te3 surface layer followed by carrier extraction into the adjacent MnBi2Te4 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 MnBi2Te4 septuple layers. The observed competition between interlayer charge transfer and intralayer phonon scattering demonstrates a method to control ultrafast charge transfer processes in MnBi2Te4-based van der Waals compounds.

Original languageEnglish
JournalNano Letters
Pages (from-to)414-421
Publication statusPublished - Jan 2023


  • density functional theory
  • magnetic topological insulators
  • MnBiTe
  • time- and angle-resolved photoemission spectroscopy
  • ultrafast carrier dynamics
  • van der Waals heterostructures


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