Interplay between strong correlations and magnetic field in the symmetric periodic Anderson model

Abstract

Magnetic-field effects in Kondo insulators are studied theoretically, using a local-moment approach to the periodic Anderson model within the framework of dynamical mean-field theory. Our main focus is on fieldinduced changes in single-particle dynamics and the associated hybridization gap in the density of states. Particular emphasis is given to the strongly correlated regime, where the dynamics is found to exhibit universal scaling in terms of a field-dependent low-energy coherence scale. Although the bare applied field is globally uniform, the effective fields experienced by the conduction electrons and the f electrons differ because of correlation effects. A continuous insulator-metal transition is found to occur on increasing the applied field, closure of the hybridization gap reflecting competition between Zeeman splitting, and screening of the f-electron local moments. For intermediate interaction strengths, the hybridization gap depends nonlinearly on the applied field, while in strong coupling its field dependence is found to be linear. For the classic Kondo insulator YbB 12 , good agreement is found upon direct comparison of the field evolution of the experimental transport gap with the theoretical hybridization gap in the density of states.

Mott transitions in the periodic Anderson model

“…36 We draw on this work in the following, and confine ourselves below to a brief summary of key features; emphasising that the TSE description used here is exact (it also underlies the local moment approach 43,19-21 but its use there, while providing a rather successful description of e.g. the PAM, [19][20][21]26,29 is in general approximate).…”

Spin-selective localization of correlated lattice fermions

“…Namely, the quasiparticle central peak between the Hubbard subbands, which originates from spin-flip scattering and thereby leads to the Kondo resonance, is destroyed when a Zeeman magnetic field is applied. [26][27][28][29][30][31][32] The induced finite magnetization reduces the number of scattering states at the Fermi level in different spin channels. Although in the present problem the magnetization is zero, 12 the density of states in the two spin bands differ, cf.…”

Field-dependent dynamics in the metallic regime of the half-filled Hubbard model

“…The two 'Hubbard bands' are just the two spin bands shifted away from the Fermi level, and broadened to an extent that they just resemble a non-interacting Gaussian DOS. In fact, the large field spectral function may be deduced from the large field asymptote of equation (13). At large field h ∼ t * , the effective field becomes comparable to or larger than the largest scale in the problem, i.e.…”

“…Within DMFT, a correlated model maps onto a single impurity model in a self-consistent conduction-electron bath. Methods like Numerical renormalization group (NRG) 10 , Local moment approach (LMA) [11][12][13] , Exact diagonalization (ED) 8 , quantum Monte Carlo (QMC) 8 , Iterative perturbation theory (IPT) [14][15][16] have been used to study the impurity problem within the DMFT framework. Motttransition has been observed in the half filled Hubbard model using DMFT 4,5 .…”