Influence of spin fluctuations near the Mott transition: a DMFT study

TL;DR

This study explores how spin fluctuations influence the Mott transition using a combined slave-rotor and DMFT approach, revealing the emergence of a spin liquid and changes in magnetic properties near the transition.

Contribution

It introduces a novel DMFT-based method incorporating slave-rotor techniques to analyze spin dynamics and the formation of spin liquids near the Mott transition.

Findings

Identification of a Sachdev-Ye spin liquid phase in the paramagnetic Mott state.

Correlation between deviations in spin susceptibility and the Mott transition line bending.

Observation of weakened exchange energy approaching the Mott boundary due to quantum fluctuations.

Abstract

Dynamics of magnetic moments near the Mott metal-insulator transition is investigated by a combined slave-rotor and Dynamical Mean-Field Theory solution of the Hubbard model with additional fully-frustrated random Heisenberg couplings. In the paramagnetic Mott state, the spinon decomposition allows to generate a Sachdev-Ye spin liquid in place of the collection of independent local moments that typically occurs in the absence of magnetic correlations. Cooling down into the spin-liquid phase, the onset of deviations from pure Curie behavior in the spin susceptibility is found to be correlated to the temperature scale at which the Mott transition lines experience a marked bending. We also demonstrate a weakening of the effective exchange energy upon approaching the Mott boundary from the Heisenberg limit, due to quantum fluctuations associated to zero and doubly occupied sites.