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Tunable quantum criticalities in an isospin extended Hubbard model simulator
Qiao Li1, Bin Cheng2, Moyu Chen1
1National Laboratory of Solid State Microstructures, School of Physics, Institute of Brain-Inspired Intelligence, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China.
Nature
|September 14, 2022
Summary
Researchers observed tunable quantum criticalities in twisted double bilayer graphene, revealing a two-stage quantum phase transition and a novel pseudo-criticality under magnetic fields. This work advances understanding of strongly correlated quantum physics.
Area of Science:
- Condensed matter physics
- Quantum materials science
- Strongly correlated electron systems
Background:
- Strong electron correlations are crucial for understanding exotic quantum phenomena.
- Quantum phase transitions (QPTs) near critical points exhibit complex behaviors beyond traditional theories.
- Moiré heterostructures offer tunable platforms for exploring strongly correlated quantum physics.
Purpose of the Study:
- To investigate tunable quantum criticalities in a chiral-stacked twisted double bilayer graphene (cTDBG) system.
- To experimentally simulate the extended Hubbard model with spin-valley isospins.
- To explore quantum critical behaviors and emergent phases in a tunable solid-state platform.
Main Methods:
- Fabrication and characterization of cTDBG moiré heterostructures.
- Experimental simulation of the extended Hubbard model.
- Scaling analysis of quantum critical points and phase transitions.
- Application of displacement fields and parallel magnetic fields to tune electronic properties.
Main Results:
- Observation of tunable quantum criticalities in cTDBG.
- Identification of a quantum two-stage criticality with two distinct QPTs during the transition from a Wigner crystal to a Fermi liquid.
- Emergence of a critical intermediate phase.
- Evolution of the two-stage criticality into a quantum pseudo-criticality under a high parallel magnetic field.
- Quantum critical scaling valid only above a critical temperature in the pseudo-critical regime, indicating a weak first-order QPT.
Conclusions:
- cTDBG serves as a highly tunable solid-state simulator for exploring complex quantum phenomena.
- The study reveals intricate interplay of multiple degrees of freedom, leading to exotic quantum critical states.
- Findings provide new insights into quantum phase transitions and critical behaviors in correlated electron systems.
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