Dynamical behavior across the Mott transition of two bands with different bandwidths

Michel Ferrero, Federico Becca, Michele Fabrizio, and Massimo Capone
Phys. Rev. B 72, 205126 – Published 23 November 2005

Abstract

We investigate the role of the bandwidth difference in the Mott metal-insulator transition of a two-band Hubbard model in the limit of infinite dimensions by means of a Gutzwiller variational wave function as well as by dynamical mean-field theory. The variational calculation predicts a two-stage quenching of the charge degrees of freedom, in which the narrower band undergoes a Mott transition before the wider one, both in the presence and in the absence of a Hund’s exchange coupling. However, this scenario is not fully confirmed by the dynamical mean-field theory calculation, which shows that, although the quasiparticle residue of the narrower band is zero within our numerical accuracy, low-energy spectral weight still exists inside the Mott-Hubbard gap, concentrated into two peaks symmetric around the chemical potential. This spectral weight vanishes only when the wider band ceases to conduct too. Although our results are compatible with several scenarios—e.g., a narrow-gap semiconductor or a semimetal—we argue that the most plausible one is that the two peaks coexist with a narrow resonance tied at the chemical potential, with a spectral weight below our numerical accuracy. This quasiparticle resonance is expected to vanish when the wider band undergoes the Mott transition.

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  • Received 4 April 2005

DOI:https://doi.org/10.1103/PhysRevB.72.205126

©2005 American Physical Society

Authors & Affiliations

Michel Ferrero1, Federico Becca1, Michele Fabrizio1,2, and Massimo Capone3,4

  • 1INFM-Democritos, National Simulation Center, and International School for Advanced Studies (SISSA), I-34014 Trieste, Italy
  • 2International Centre for Theoretical Physics (ICTP), P.O. Box 586, I-34014 Trieste, Italy
  • 3INFM-SMC and Dipartimento di Fisica, Università di Roma “La Sapienza,” Piazzale Aldo Moro 2, I-00185 Roma, Italy
  • 4Istituto dei Sistemi Complessi del CNR, via dei Taurini 19, I-00185 Roma, Italy

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Issue

Vol. 72, Iss. 20 — 15 November 2005

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