Reliability of the one-crossing approximation in describing the Mott transition

V. VILDOSOLA; LEONID POUROVSKII; L. O. MANUEL; P. ROURA BAS

JOURNAL OF PHYSICS CONDENSED MATTER

IOP PUBLISHING LTD

Lugar: Londres; Año: 2015 vol. 27

0953-8984

We assess the reliability of the one-crossing approximation (OCA) approach in a quantitativedescription of the Mott transition in the framework of the dynamical mean field theory(DMFT). The OCA approach has been applied in conjunction with DMFT to a number ofheavy-fermion, actinide, transition metal compounds and nanoscale systems. However, severalrecent studies in the framework of impurity models pointed out serious deficiencies of OCAand raised questions regarding its reliability. Here we consider a single band Hubbard modelon the Bethe lattice at finite temperatures and compare the results of OCA to those of anumerically exact quantum Monte Carlo (QMC) method. The temperature-local repulsion Uphase diagram for the particle-hole symmetric case obtained by OCA is in good agreement withthat of QMC, with the metal?insulator transition captured very well. We find, however, that theinsulator to metal transition is shifted to higher values of U and, simultaneously, correlationsin the metallic phase are significantly overestimated. This counter-intuitive behaviour is dueto simultaneous underestimations of the Kondo scale in the metallic phase and the size of theinsulating gap. We trace the underestimation of the insulating gap to that of the second momentof the high-frequency expansion of the impurity spectral density. Calculations of the systemaway from the particle-hole symmetric case are also presented and discussed.