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Strong Coupling Limit of the Holstein-Hubbard Model
Zhaoyu Han1, Steven A Kivelson1, Hong Yao1,2
1Department of Physics, Stanford University, Stanford, California 94305, USA.
Physical Review Letters
|October 30, 2020
Summary
We mapped the quantum phase diagram of the Holstein-Hubbard model, revealing novel phases like pair-density waves and exotic superconductors with charges 4e and 6e. The study details transitions influenced by interaction strength and phonon frequency.
Area of Science:
- Condensed Matter Physics
- Quantum Materials
- Strongly Correlated Systems
Background:
- The Holstein-Hubbard model is a fundamental framework for understanding interacting electrons coupled to lattice vibrations.
- Exploring its quantum phase diagram is crucial for predicting novel electronic states.
Purpose of the Study:
- To investigate the complex quantum phase diagram of the Holstein-Hubbard model.
- To identify and characterize exotic electronic phases, including unconventional superconductivity and density waves.
Main Methods:
- Utilizing an asymptotically exact strong coupling expansion.
- Analyzing the model's behavior as a function of interaction strength and phonon frequency (retardation).
Main Results:
- Discovery of a pair-density wave phase.
- Identification of unconventional superconducting states with charge 4e and charge 6e.
- Observation of distinct charge-density-wave and spin-density-wave regimes.
- Mapping of phase separation boundaries.
- Characterization of crossovers driven by the degree of retardation.
Conclusions:
- The strong coupling expansion provides a powerful tool for uncovering rich physics in the Holstein-Hubbard model.
- Exotic electronic phases, including multi-charged superconductivity, emerge under specific interaction and phonon coupling conditions.
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