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Can correlations drive a band insulator metallic?
Arti Garg1, H R Krishnamurthy, Mohit Randeria
1Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai 400005, India.
Physical Review Letters
|August 16, 2006
Summary
We studied how electron interactions affect band insulators using dynamical mean-field theory. We discovered a critical interaction strength where the insulating gap closes, leading to a metal, followed by a transition to a Mott insulator.
Area of Science:
- Condensed matter physics
- Materials science
Background:
- Understanding electron correlation effects is crucial for predicting material properties.
- Band insulators transition to metallic or other correlated states under certain conditions.
Purpose of the Study:
- To investigate the impact of on-site Coulomb repulsion (U) on a band insulator.
- To compare dynamical mean-field theory (DMFT) predictions with Hartree-Fock theory.
Main Methods:
- Dynamical Mean-Field Theory (DMFT) was employed to model the system.
- The behavior of the insulating gap was analyzed as a function of Coulomb repulsion (U).
Main Results:
- A critical value (Uc1) was identified where the insulating gap closes, leading to a metallic phase.
- A second critical value (Uc2) marks a transition back to a Mott insulator, with the gap increasing with U.
- These findings contrast with Hartree-Fock theory, which predicts a continuously decreasing, non-zero gap.
Conclusions:
- DMFT reveals a complex interplay between electron correlation and insulating behavior.
- The metal-insulator transitions exhibit non-trivial behavior not captured by simpler theories like Hartree-Fock.
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