An optical data storage medium comprises a super-resolution (SR) layer consisting of thermoelectric material, said SR layer having light absorption, transmittance and reflectance at the wavelength of an incident light and maintaining a crystalline single phase without a structural or chemical change below the melting temperature of the material. SR readout of data from and/or SR writing of data onto the medium is carried out by way of thermoelectrically induced optical changes within a local area of the SR layer under laser irradiation.