The tilt effect in the electron-phonon interaction with finite relaxation times of the electrons

A theoretical study of the tilt effect is presented namely the dependence of the longitudinal sound absorption and velocity on the angle between the magnetic field and the propagation vector. As has been shown, the tilt effect is a strong nonadiabatic effect which does not contain the small parameter s/v. The influence of the finite electron relaxation time on the singularities of the absorption and of the sound velocity is investigated. The tilt effect proves to be well-distinguishable if the condition ωτ > 1 is satisfied.     

Observation of intrinsic spin-lattice relaxation of conduction electrons in metallic lithium

Temperature dependent intrinsic spin relaxation of conduction electrons in lithium observed via a spin-echo method is reported. Experimental results obtained are likely to correspond to a spin-current relaxation mechanism predicted earlier by Overhauser.     

Laser short-pulse heating of silicon film with the presence of metallic substrate

Laser interaction of silicon film located at he top of metallic substrate is examined and energy transport in electron and lattice sub-systems are formulated using the electron kinetic theory approach. The simulations are repeated for different substrate materials, namely gold, silver, and copper. It is found that electron temperature in the silicon film rises in the vicinity of the silicon–metallic substrate interface, despite the fact that energy absorption from the irradiated filed is significantly low in the silicon film. Lattice site temperature rises rapidly in the early heating period at the interface. In addition, lattice site temperature increase is higher in the silicon film than that corresponding to the metallic substrate.     

On the theory of relaxation of electrons excited by femtosecond laser pulses in thin metallic films

Received: 14 October 1998 / Revised version: 21 December 1998     

Importance of electron-phonon processes in the inelastic lifetime of conduction electrons

The temperature of conduction electrons can be raised above the lattice temperature by a high electric current density. The achieved temperature difference is proportional to the electron-phonon relaxation time. Weak localization yields information about the electron temperature and allows the conclusion that electron-phonon processes are an essential determinant for the inelastic lifetime of the conduction electrons.     

Fermi energy of electrons in a thin metallic plate

A strict analytical expression for the Fermi energy of electrons in a thin metallic plate as a function of the plate thickness at a given electron density has been derived for the first time. The derivation has been carried out taking into account the size quantization in the free-electron approximation at zero temperature.     

Size-dependence of the effective electron-phonon energy relaxation in hollow gold nanospheres

In this paper the size-dependence of energy relaxation, which is induced by the electron-phonon (e-ph) interactions and the electron-surface (e-s) interactions in noble metal nanoparticles, is investigated. Then based on the analysis and the derivation of the e-s coupling constant in metal nanospheres, the formula of the effective electron-phonon coupling constant G_eff of hollow gold nanospheres (HGNs) is deduced. Moreover, the correctness of the formulae gets proved by contrast analyses of the calculated G_eff values and experimental values obtained from literature.     

The near field correlation spectrum of a metallic film

The spatial two-point coherence function of the thermal radiation field at subwave-distance from a metallic film is calculated within fluctuation electrodynamics. Long-range oscillations as a function of lateral separation are seen; we interpret their features by comparing to the dispersion relations of surface plasmon polariton modes on the thin film. The hybridization of the surface modes on the top and bottom interfaces leads to a beatnote in the field correlations, for specific detector setups.     

Spin relaxation of two-dimensional electrons in a hall ferromagnet

Electron spin resonance in a system of two-dimensional electrons with a high electron mobility has been investigated and the position, width, intensity, and line shape of the resonance microwave absorption have been studied as functions of the filling factor and temperature. It has been shown that the ESR linewidth in high-electron-mobility GaAs/AlGaAs quantum wells may reach 30 MHz, which corresponds to a spin relaxation time of the two-dimensional electrons of 10 ns. The experimental data on the linewidth of the spin resonance at a filling factor of 1 are compared with the theoretical results for various spin relaxation mechanisms. It has been shown that the dominant mechanism of spin relaxation at a filling factor of 1 and a temperature of 1.5–4 K is the mutual scattering of spin excitons.     

The effect of phonon focusing on the electron-phonon relaxation and electron transport in potassium crystals

The influence of anisotropy of elastic energy on electron-phonon relaxation and the role of shear waves in the electrical resistance of potassium crystals are investigated. It is shown that, at temperatures much lower than the Debye temperature (T<< θ_D), the contribution of slow quasi-transverse phonons to the electrical resistance of potassium crystals exceeds that of longitudinal phonons by an order of magnitude. Earlier, the Bloch-Grüneisen theory left aside this component under the above conditions. At the same time, at high temperatures(T>>θ_D), the contribution of longitudinal phonons to the electrical resistance turns out to be 4 times greater than the total contribution of electron relaxation by fast and slow transverse modes. The role of shear waves in the electrical resistance of potassium crystals is analyzed. It is shown that, at low temperatures, this mechanism provides 32% of the total electrical resistance. It is 4 times higher than the contribution of longitudinal phonons to the electrical resistance and should be taken into account when analyzing the electrical resistance of alkali metals. The distribution function of the most effective phonons for electrical resistance is defined, and the inelasticity of electron-phonon scattering is analyzed. It is shown that the calculated results of the electrical resistance of potassium in the temperature range from 40 to 400 K, taking into account the anisotropy of elastic energy, are in good agreement with the experimental data without the use of fitting parameters.     

The effect of instantaneous diffusion on the relaxation of photon echoes in ruby

It has been recently suggested that electrid dipole instantaneous diffusion plays an important role in the relaxation of photon echoes in ruby. Our experiments indicate that instantaneous diffusion is not important in this relaxation.     

Alternating-current relaxation of a rotating metallic particle

Based on a first-principles approach,we establish an alternating-current(AC) relaxation theory for a rotating metallic particle with complex dielectric constant ε_α=ε_α-iσ_α/ω_0.Here εα is the real part,σ_α the conductivity,ω_0 the angular frequency of an AC electric field,and i=-1~(1/2).Our theory yields an accurate interparticle force,which is in good agreement with the existing experiment.The agreement helps to show that the relaxations of two kinds of charges,namely,surface polarized charges(described by ε_α) and free charges(corresponding to σ_α),contribute to the unusually large reduction in the attracting interparticle force.This theory can be adopted to determine the relaxation time of dynamic particles in various fields.     

脉冲激光烧蚀中电声弛豫时间的确定

为了提高脉冲激光制备薄膜的质量,准确掌握电声弛豫时间是关键,它对脉冲激光脉宽和能量密度的选取起着决定性的作用. 文中以铝靶材为例,利用经典的双温方程通过时域有限差分法(FDTD)得到电子、离子亚系统的温度随时间和位置演化的图像,进而得到电声弛豫时间的准确值. 这样便能准确划分热烧蚀和非平衡烧蚀,从而更好地控制激光的烧蚀过程. 同时找出了电声弛豫时间随激光脉宽以及能量密度变化的规律. 关键词： 飞秒激光 电声弛豫时间 双温方程 激光能量密度     

Optical interaction in a plasmonic metallic particle chain coupled to a metallic film

We study the coupling of localized surface plasmon and surface plasmon polariton modes in a system composed of a metallic nanoparticle chain imbedded in a dielectric–metal–dielectric substrate. The results show the influence of outside parts and imbedded parts of particles on the interaction between localized surface plasmon and surface plasmon polariton modes. An enhancement can be observed in our structure. This kind of the structure has a very promising candidate for biosensing and surface enhanced spectroscopy applications.     

Laser acceleration of electrons in a thin metal film

A mechanism acceleration of electrons to relativistic velocities in a thin metal film irradiated with ultrashort (τ _L ≤1 ps) high-power (I>¹⁶ W/cm²) laser pulses is proposed. The acceleration is due to a resonance action of the nonuniform field on a portion of the electrons, viz., those which oscillate in the direction transverse to the film with a frequency close to the frequency of the field. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 8–12 (10 July 1997)