Chiral magnetic current turns nonlinear near a phase boundary

Using the D3/D7 brane system in holography, the authors map how chiral magnetic current responds to an external magnetic field across a phase boundary separating an insulating phase from a chiral magnetic effect phase. Rather than a simple proportional relationship, the current becomes multi-valued near the transition — a signature of strong nonlinearity. They also find that an axial chemical potential and magnetic field together stabilize the insulating phase cooperatively. The results expose richer phase structure in chiral transport than linear-response calculations capture.