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arXiv · 2209.07344

Tunable quantum criticalities in an isospin extended Hubbard model simulator

Qiao Li·Bin Cheng·Moyu Chen·Bo Xie·Yongqin Xie·Pengfei Wang·Fanqiang Chen·Zenglin Liu·Kenji Watanabe·Takashi Taniguchi·Shi-Jun Liang·Da Wang·Chenjie Wang·Qiang-Hua Wang·Jianpeng Liu·Feng Miao
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Abstract

Studying strong electron correlations has been an essential driving force for pushing the frontiers of condensed matter physics. In particular, in the vicinity of correlation-driven quantum phase transitions (QPTs), quantum critical fluctuations of multiple degrees of freedom facilitate exotic many-body states and quantum critical behaviors beyond Landau's framework. Recently, moir\'e heterostructures of van der Waals materials have been demonstrated as a highly tunable quantum platform for exploring fascinating strongly correlated quantum physics. Here, we report the observation of tunable quantum criticalities in an experimental simulator of extended Hubbard model with spin-valley isospins arising in chiral-stacked twisted double bilayer graphene. Scaling analysis shows a quantum two-stage criticality manifesting two distinct quantum critical points as the generalized Wigner crystal transits to a Fermi liquid by varying the displacement field, suggesting the emergence of a critical intermediate phase. The quantum two-stage criticality evolves into a quantum pseudo criticality as a high parallel magnetic field is applied. In such pseudo criticality, we find that the quantum critical scaling is only valid above a critical temperature, indicating a weak first-order QPT therein. Our results demonstrate a highly tunable solid-state simulator with intricate interplay of multiple degrees of freedom for exploring exotic quantum critical states and behaviors.

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Qiao Li, Bin Cheng, Moyu Chen, Bo Xie, Yongqin Xie, Pengfei Wang, Fanqiang Chen, Zenglin Liu, Kenji Watanabe, Takashi Taniguchi, Shi-Jun Liang, Da Wang, Chenjie Wang, Qiang-Hua Wang, Jianpeng Liu, Feng Miao. 2022-09-15. Tunable quantum criticalities in an isospin extended Hubbard model simulator. https://doi.org/10.1038/s41586-022-05106-0

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