HYDRODYNAMIC FLUCTUATIONS OF A HOT-ELECTRON GAS

Hydrodynamical fluctuations of the electron gas comprise low-frequency and long-range stochastic excitations over a steady state of the syst em. In this work we develop the theory of hydrodynamic fluctuations in the nonequilibrium electron gas which can be described by its electro n temperature. For this case the characteristic spatial-time parameter s are the electric charge decay time tau(M), the electron temperature relaxation time tau(T), and two corresponding diffusion lengths L(M) a nd L(T), respectively. The spectral densities of the fluctuations are found and investigated for arbitrary relationships between the fluctua tion frequency omega and times tau(M) and tau(T), for wave vectors q a nd lengths L(M), L(T). In the first case, we established the effect of the crossover correlation of the electron density delta n(r,t) and te mperature delta T(r,t) fluctuations. The cross correlation depends on omega and changes its sign, which indicates the existence of the frequ ency range of correlation and anticorrelation of delta n (r,r) and del ta T(r,t). In the general case, spectral densities of the fluctuations have non-lorentz form, which also holds with thermal equilibrium, At the equilibrium the cross-correlation effect leads to only redistribut ion of the fluctuation intensity over the frequency region. Under none quilibrium conditions the cross correlation also changes the integral intensities of the fluctuations and is directly related to additional kinetic correlation of the hot electrons caused by electron-electron i nteraction. The results are applied to the calculation of light scatte ring by electron plasma fluctuations. The cross-correlation effect giv es the essential contribution to the doss section of the light scatter ing. It is shown that the additional kinetic correlation of hot electr ons can be directly measured by means of the light-scattering experime nt.