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Phase separation close to the density-driven Mott transition in the Hubbard-Holstein model
M Capone1, G Sangiovanni, C Castellani
1Enrico Fermi Center, Rome, Italy.
Physical Review Letters
|April 20, 2004
Summary
Dynamical mean-field theory reveals that electron-phonon coupling in the Hubbard-Holstein model causes phase separation during a Mott transition. Intermediate coupling enhances metallic compressibility, while strong coupling leads to a polaronic phase.
Area of Science:
- Condensed matter physics
- Quantum mechanics
- Materials science
Background:
- The Mott transition describes a phase transition in materials where electron-electron interactions cause an insulator to become a conductor.
- The Hubbard-Holstein model combines Mott physics with electron-phonon interactions, crucial for understanding real materials.
Purpose of the Study:
- To investigate the impact of electron-phonon coupling on the density-driven Mott transition.
- To explore the resulting phases and their properties at zero temperature.
Main Methods:
- Dynamical mean-field theory (DMFT) was employed to solve the Hubbard-Holstein model.
- The study focused on the T=0 phase diagram and compressibility.
Main Results:
- An intermediate electron-phonon coupling strength induces a first-order Mott transition with phase separation between metallic and insulating states.
- Metallic phase compressibility is significantly enhanced under these conditions.
- At larger coupling strengths, a polaronic phase emerges, coexisting with a nonpolaronic metal.
Conclusions:
- Electron-phonon interactions play a critical role in modifying the nature of the Mott transition.
- The Hubbard-Holstein model provides a framework for understanding complex phase behaviors driven by both electronic and lattice degrees of freedom.