Orbital selective Mott transition in multi-band systems: slave-spin representation and dynamical mean-field theory

Details Orbital selective Mott transition in multi-band systems: slave-spin representation and dynamical mean-field theory Orbital selective Mott transition in multi-band systems: slave-spin representation and dynamical mean-field theory

2005-03-31

arxiv.org/abs/cond-mat/0503764v2

Phys. Rev. B 72, 205124 (2005)

Physics

Condensed Matter

Strongly Correlated Electrons

Discussion on the effect of hybridization on the OSMT has been extended

Scientific paper

10.1103/PhysRevB.72.205124

We examine whether the Mott transition of a half-filled, two-orbital Hubbard model with unequal bandwidths occurs simultaneously for both bands or whether it is a two-stage process in which the orbital with narrower bandwith localizes first (giving rise to an intermediate `orbital-selective' Mott phase). This question is addressed using both dynamical mean-field theory, and a representation of fermion operators in terms of slave quantum spins, followed by a mean-field approximation (similar in spirit to a Gutzwiller approximation). In the latter approach, the Mott transition is found to be orbital-selective for all values of the Coulomb exchange (Hund) coupling J when the bandwidth ratio is small, and only beyond a critical value of J when the bandwidth ratio is larger. Dynamical mean-field theory partially confirms these findings, but the intermediate phase at J=0 is found to differ from a conventional Mott insulator, with spectral weight extending down to arbitrary low energy. Finally, the orbital-selective Mott phase is found, at zero-temperature, to be unstable with respect to an inter-orbital hybridization, and replaced by a state with a large effective mass (and a low quasiparticle coherence scale) for the narrower band.

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