Elimination of the mott interband s-d enhancement of the electrical resistance of nickel and platinum owing to the excitation of electrons by femtosecond laser pulses

Abstract

The dependence of electrical, σ, and thermal, κ, conductivities of metals on the electron temperature T _e at high (∼1 eV) T _e values has been calculated. The two-temperature states for which the temperature T _e of heated electrons exceeds the temperature T _i of ions in the crystal lattice result from the excitation of electrons by femtosecond laser pulses. It is well known that the existence of empty d levels with a high density of states near the Fermi surface (as, e.g., in nickel, platinum, and iron) leads to a pronounced enhancement of the electrical resistance (Mott, 1936). This is due to an increase in the statistical factor related to the electron transitions to the empty states induced by collisions with phonons. It is found that the excitation of the electron subsystem significantly reduces the electron-phonon scattering to unoccupied d states since the chemical potential μ(T _e ) rises above the upper edge of the d band. The decrease in the scattering probability leads to the anomalous behavior of the conductivity σ_el-ph, which increases with the temperature T _e . Such a behavior turns out to be inverse with respect to the usual situation in condensed matter.