After modeling the surface gap, the bulk gap, and the electrode-material interface gap, and considering the effect of spin-orbit coupling strength on the effective mass, we reveal that the surface quasipolarons at the edge states are the main charge carrier of nonlinear photocurrent in a double perovskite family of ${\mathrm{Ca}}_{\mathrm{x}}{\mathrm{Cu}}_{4-x}{\mathrm{Ti}}_4{\mathrm{O}}_{12}$ ($x=3$, 2, and 1). The photocurrent is the quadratic function of voltage, which is measured in two ways of the bulk mode and the surface mode, in the visible light with the wavelength of 385, 405, 450 and 660 nm and at the temperature of 150, 180, 210, 240, 270, and 300 K, respectively. When there is the electrode effect, we discuss the electron-phonon coupling, the spin-orbit coupling, the effective mass, the flat band, and the quasipolaron size. Particularly in the surface mode, we estimate the spin-orbit coupling and the electron-phonon coupling. The computational and experimental results suggest that the antiferromagnetically dielectric insulator in the ceramic form is a potential candidate for broad-spectrum and wide-temperature-range photodetectors.

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• Dielectric properties
• Photocurrent
• Polarons
• Spin optoelectronics
• Antiferromagnets
• Ceramics
• Magnetic insulators