THz Nano-Imaging Reveals Magnetic Melting of Charge Order Across the Colossal Magnetoresistance Transition

Strongly correlated electronic materials, such as colossal magnetoresistive (CMR) manganites, serve as model systems for studying the melting of charge and orbital order (CO/OO) under external stimuli. Prior equilibrium and time-resolved studies have probed spatially averaged responses, overlooking nanoscale inhomogeneity across the CMR transition. Here, we investigate nanoscale melting of CO/OO in a perovskite manganite using cryogenic magneto-THz scattering-type scanning near-field optical microscopy (cm-THz-sSNOM). We observe the collapse of charge order driven by antiferromagnetic-to-ferromagnetic spin reordering under applied magnetic fields, accompanied by a continuous transition from a CO insulating state to a CO metallic phase. Near-field imaging under varying fields reveals nanometer-scale conductivity variations that track the growth of spin-reordering. These results provide direct nanoscale insights into the CMR phase transformation and demonstrate THz nano-spectroscopy as a powerful platform to probe correlated electronic and magnetic phase transitions beyond the reach of conventional techniques.