Dresden 2009 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 15: Correlated Electrons: Metal-Insulator Transition 2

TT 15.7: Talk

Tuesday, March 24, 2009, 11:15–11:30, HSZ 301

Mott transitions at variable spin/orbital degeneracy — •Nils Blümer and Elena Gorelik — Institut für Physik, Universität Mainz, Mainz, Germany

The Mott transition between a metal and a paramagnetic insulator is central to the field of strongly correlated electron systems. Much insight into this phenomenon has been gained in numerical studies of the 1-band Hubbard model within dynamical mean-field theory (DMFT). In particular, the phase diagram and the behavior of characteristic observables (such as the effective mass) have been established with high precision - despite the lack of analytic solutions. The physics of multiorbital models is richer (including the possibility of orbital-selective Mott transitions), but also much more challenging.

However, exact analytical results have been derived for the SU(2M) symmetric Hubbard model (where all spins/orbitals are equivalent) in the limit of large band multiplicity M→∞ [1]. So far, these predictions have only been checked/complemented by self-energy functional calculations with one bath site per orbital [2]; this method has quite substantial errors in the 1- band case [3].

We present numerically exact multigrid Hirsch-Fye quantum Monte Carlo estimates of the phase boundaries at half filling and for up to M=8 bands. We also derive scaling laws which predict the phase boundaries for arbitrary orbital degeneracy M with high accuracy.

[1] S. Florens et al., Phys. Rev. B 66, 205102 (2002).

[2] K. Inaba et al., Phys. Rev. B 72, 085112 (2005).

[3] K. Požgajčić, arXiv:cond-mat/0407172v1 (2004).