Spin-liquid Mott quantum criticality: Emergence of localized magnetic moments

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 Landauu0027s 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.