Localized dynamic perturbations in metals

Kurt Schönhammer

O. Gunnarsson, Kurt Schönhammer

Recently we proposed two boson approximations to describe the creation of electronhole---pair excitations by a localized time-dependent perturbation. These boson approximations were shown to be exact in certain limiting cases. In this paper we compare the results in these approximations with exact calculations where the electrons are treated as fermions. We show that the validity of the approximations is broader than had earlier been proven.

克之 阿波

David Pines

Jae-Ho Han, Yong-Heum Cho, Ki‐Seok Kim

Emergence of localized magnetic moments in the vicinity of a metal-insulator transition is a non-perturbative phenomenon beyond the description based on the perturbative theoretical framework. Resorting to a recently developed theoretical device called dimensional regularization for the Fermi-surface problem, we examine a metal-insulator quantum phase transition from a Landau's Fermi-liquid state to a U(1) spin-liquid phase with a spinon Fermi surface in two dimensions. Assuming that the spinon Fermi surface can be destabilized across the spin-liquid Mott quantum critical point, we show that such itinerant spinons become localized to result in localized magnetic moments near the spin-liquid Mott quantum critical point. The role of such emergent moments in non-Fermi liquid physics reveals the nature of spin-liquid Mott quantum criticality as novel local quantum criticality, where critical charge dynamics belongs to the inverted XY universality class and critical spin dynamics conforms to a locally critical universality class.

J. R. Schrieffer