Zoom link:
https://umich.zoom.us/j/91655313495 with the passcode: CM-AMO

ABC-stacked trilayer graphene/hexagonal boron nitride moiré superlattice (TLG/hBN) has emerged as a playground for correlated electron physics. A spectroscopy study of this system is, however, challenging due to the device configuration. In this talk, I will introduce our recent efforts on FTIR photocurrent spectroscopy measurements of dual-gated TLG/hBN. We observed strong gate-tunable optical transitions that originated from the moire flat band. At half-filling of the valence flat band, a broad absorption peak emerges at ~18 meV, indicating direct optical excitation across an emerging Mott gap. Furthermore, I will talk about a unique moire-enabled interlayer electron-phonon coupling phenomenon in this system. The ZO phonon in hBN hybridizes with electron-hole excitations in trilayer graphene and appear as an asymmetric peak in the photocurrent spectrum. This Fano line-shaped peak evolves continuously as we tune the displacement field. I'll talk about the implications of this phenomenon to engineering the physics of moire quantum matters.