Visualizing incommensurate inter-valley coherent states in rhombohedral trilayer graphene

ABC-stacked rhombohedral graphene multilayers exhibit a wide variety of electronic ground states characterized by broken isospin symmetry and superconductivity. Recently, indirect evidence of inter-valley coherent (IVC) order has been reported in rhombohedral trilayer graphene (RTG), with possible i...

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Published in:arXiv.org 2024-11
Main Authors: Liu, Yiwen, Gupta, Ambikesh, Choi, Youngjoon, Yaar Vituri, Stoyanov, Hari, Xiao, Jiewen, Wang, Yanzhen, Zhou, Haibiao, Barick, Barun, Taniguchi, Takashi, Watanabe, Kenji, Binghai Yan, Berg, Erez, Young, Andrea F, Beidenkopf, Haim, Avraham, Nurit
Format: Article
Language:English
Subjects:
Charge density
Chemical potential
Electrons
Elementary excitations
Graphene
Ground state
Hole density
Multilayers
Phase transitions
Scanning tunneling microscopy
Superconductivity
Symmetry
Unit cell
Valence band
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Summary:ABC-stacked rhombohedral graphene multilayers exhibit a wide variety of electronic ground states characterized by broken isospin symmetry and superconductivity. Recently, indirect evidence of inter-valley coherent (IVC) order has been reported in rhombohedral trilayer graphene (RTG), with possible implications for the origin of superconductivity. Here, we report the direct visualization of IVC order in RTG using scanning tunneling microscopy and spectroscopy. Tuning the chemical potential through the Van Hove singularity near the edge of the valence band, we observe a cascade of phase transitions associated with the formation of half- and quarter-metal states. IVC phases, distinguished by an enlarged real space unit cell, are directly imaged near both the high- and low-density boundaries of the half-metal phase. At high hole density, we precisely reconstruct the IVC band structure through quasiparticle interference. Intriguingly, the charge density modulations reveal a C3-symmetric incommensurate IVC order that agrees with the recent prediction of an IVC-crystal phase. Our findings demonstrate that IVC phases are a widespread symmetry-broken ground state within graphene systems.
ISSN:2331-8422