Ultrafast coherent interlayer phonon dynamics in atomically thin layers of MnBi2Te4

Abstract

The atomically thin MnBi2Te4 crystal is a novel magnetic topological insulator, exhibiting exotic quantum physics. Here we report a systematic investigation of ultrafast carrier dynamics and coherent interlayer phonons in few-layer MnBi2Te4 as a function of layer number using time-resolved pump-probe reflectivity spectroscopy. Pronounced coherent phonon oscillations from the interlayer breathing mode are directly observed in the time domain. We find that the coherent oscillation frequency, the photocarrier and coherent phonon decay rates all depend sensitively on the sample thickness. The time-resolved measurements are complemented by ultralow-frequency Raman spectroscopy measurements, which both confirm the interlayer breathing mode and additionally enable observation of the interlayer shear mode. The layer dependence of these modes allows us to extract both the out-of-plane and in-plane interlayer force constants. Our studies not only reveal the interlayer van der Waals coupling strengths, but also shed light on the ultrafast optical properties of this novel two-dimensional material.

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Cited by in corpus (7)

• Observation of the Axion quasiparticle in 2D MnBi${}_2$Te${}_4$
• Strong Coupling of Coherent Phonons to Excitons in Semiconducting Monolayer MoTe${}_2$
• Real-time observation of magnetization and magnon dynamics in a two-dimensional topological antiferromagnet MnBi2Te4
• Fabrication-induced even-odd discrepancy of magnetotransport in few-layer MnBi${}_2$Te${}_4$
• Time-domain study of coupled collective excitations in quantum materials
• Localization of vibrational modes in high-entropy oxides
• Research on topological materials using ultrafast spectroscopy