Laser-induced grating spectroscopy of electron-phonon interaction in metallic and high-temperature superconductors

Abstract

We propose a new spectroscopical method for the investigation of electron-phonon (EP) interaction on subpicosecond time scale in metallic and high-temperature (HT) superconductors by using a tunable laser beam, without requiring femtosecond laser pulses or optical detectors. The method is based on the self-diffraction of a laser beam from a laser-induced temperature moving gratings, and on the close connection between EP interaction and thermal relaxation of hot carriers. The theory of the method has been developed in detail. Two regimes have been considered: (a) the regime of weak heating of the electron system and (b) the regime of strong heating of the electron system. It has been shown that for regime (a) the proposed method permits to measure the EP interaction constant that determines the superconducting transition temperature in the metallic superconductors. In regime (b) the suggested method permits both the determination of the EP interaction constant and the direct measurement of the dependence of thermal electron relaxation on temperature. Such measurements can provide pertinent information about the contribution of the EP interaction to the HT superconductivity.