Spectroscopy signatures of electron correlations in a trilayer graphene/hBN moiré superlattice

• DOI: 10.1126/science.abg3036
• Publication Date: 2022-03-17T17:59:18Z
• Authors: Jixiang Yang; Guorui Chen; Tianyi Han; Qihang Zhang; Ya-Hui Zhang; Lili Jiang; Bosai Lyu; Hongyuan Li; Kenji Watanabe; Takashi Taniguchi; Zhiwen Shi; Todadri Senthil; Yuanbo Zhang; Feng Wang; Long Ju
• Keywords: 0301 basic medicine; Condensed Matter - Strongly Correlated Electrons; 03 medical and health sciences; Condensed Matter - Mesoscale and Nanoscale Physics; Strongly Correlated Electrons (cond-mat.str-el); General Science & Technology; Physical Sciences; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 500; FOS: Physical sciences; Condensed Matter Physics; 530

ABC-stacked trilayer graphene/hexagonal boron nitride moiré superlattice (TLG/hBN) has emerged as a playground for correlated electron physics. We report spectroscopy measurements of dual-gated TLG/hBN using Fourier transform infrared photocurrent spectroscopy. We observed a strong optical transition between moiré minibands that narrows continuously as a bandgap is opened by gating, indicating a reduction of the single-particle bandwidth. At half-filling of the valence flat band, a broad absorption peak emerges at ~18 milli–electron volts, indicating direct optical excitation across an emerging Mott gap. Similar photocurrent spectra are observed in two other correlated insulating states at quarter- and half-filling of the first conduction band. Our findings provide key parameters of the Hubbard model for the understanding of electron correlation in TLG/hBN.