- Zhang, Hongyun;
- Wang, Shuopei;
- Wang, Eryin;
- Lu, Xiaobo;
- Li, Qian;
- Bao, Changhua;
- Deng, Ke;
- Zhang, Haoxiong;
- Yao, Wei;
- Chen, Guorui;
- Fedorov, Alexei V;
- Denlinger, Jonathan D;
- Watanabe, Kenji;
- Taniguchi, Takashi;
- Zhang, Guangyu;
- Zhou, Shuyun
Electron-electron interaction is fundamental in condensed matter physics and can lead to composite quasiparticles called plasmarons, which strongly renormalize the dispersion and carry information of electron-electron coupling strength as defined by the effective fine structure constant αee*. Although h-BN with unique dielectric properties has been widely used as an important substrate for graphene, so far there is no experimental report of plasmarons in graphene/h-BN yet. Here, we report direct experimental observation of plasmaron dispersion in graphene/h-BN heterostructures through angle-resolved photoemission spectroscopy (ARPES) measurements upon in situ electron doping. Characteristic diamond-shaped dispersion is observed near the Dirac cone in both 0° (aligned) and 13.5° (twisted) graphene/h-BN, and the electron-electron interaction strength αee* is extracted to be αee*≈0.9±0.1, highlighting the important role of electron-electron interaction. Our results suggest graphene/h-BN as an ideal platform for investigating strong electron-electron interaction with weak dielectric screening, and lays fundamental physics for gate-tunable nano-electronics and nano-plasmonics.