Correlation-Driven Nonlinear Magnetoelectric Response in an Altermagnet: A Dynamical Mean-Field Study

Abstract

We investigate the optical nonlinear magnetoelectric effect (NMEE) in a strongly correlated altermagnet using dynamical mean-field theory. Unlike effective band descriptions with an imposed spin splitting, our approach determines the altermagnetic order, electronic spectrum, and optical nonlinear response self-consistently. We find that the NMEE is finite in the altermagnetic phase and vanishes in the paramagnetic phase. Its frequency dependence reflects the spin-resolved spectral structure and provides an estimate of the characteristic altermagnetic spin-splitting scale. Interaction and temperature tuning produce qualitatively different behavior: at low temperature, reducing the interaction strength toward the interaction-driven magnetic phase boundary enhances the response, whereas increasing the temperature suppresses it and drives it to zero above the critical temperature. These results establish the optical NMEE as a probe of correlated altermagnetic order and suggest that tuning parameters such as pressure, strain, or chemical substitution toward an interaction-driven phase boundary may provide a promising route to maximizing the response.