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First-order pairing transition and single-particle spectral function in the attractive hubbard model
M Capone1, C Castellani, M Grilli
1Dipartimento di Fisica, Università di Roma La Sapienza, and INFM Center for Statistical Mechanics and Complexity, Piazzale Aldo Moro 2, I-00185 Roma, Italy.
Physical Review Letters
|March 23, 2002
Summary
This study reveals a first-order phase transition in the attractive Hubbard model, shifting from a metallic Fermi liquid to an insulating bound pairs state. This transition, occurring at specific electron densities, involves phase separation and changes in spectral function features.
Area of Science:
- Condensed Matter Physics
- Quantum Many-Body Theory
Background:
- The attractive Hubbard model is a fundamental model for understanding phenomena like superconductivity.
- Investigating the normal phase is crucial for a complete understanding of the model's phase diagram.
Purpose of the Study:
- To analyze the attractive Hubbard model in its normal phase, excluding superconducting states.
- To identify and characterize phase transitions and their associated properties.
Main Methods:
- Dynamical Mean-Field Theory (DMFT) was employed.
- Solutions were restricted to exclude superconducting order parameters.
Main Results:
- A first-order phase transition was identified at all electron densities away from half-filling.
- The transition occurs between a metallic Fermi liquid (for coupling U < U(c)) and an insulating bound pairs phase (for U > U(c)).
- Phase separation accompanies this transition, and the spectral function shows a discontinuous change at the critical coupling U(c).
Conclusions:
- The attractive Hubbard model exhibits a distinct pairing transition in the normal phase.
- The transition leads to the formation of bound pairs and phase separation, altering the electronic spectral properties.