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AND $EETINGS CONFEREN

of}l9_tfp.,?nlffi February 1e83) sciences
PACSnumbers:01.10.Fv An expanded session of the executive of the Division and Astronomy {tas held on Februd General Physics 16, 1983, at the Institute of Solid State Physics, rry Sciences of the USSR (Chernogolovka, ,tcademy of to MoscowDistrict), 'fhe celebrate the 20th anniversary session heard the following rerf the Institute.

glpandedsession of the executiveof the Division of Physics and Astronomy of the Academy of General

Institute of Solid State Physics. 3. V. F. Gantmahher. Low-temperature kinetics of conduction electrons in metals and semiconductors. 4. E. G. Ponyatoushil. High-pressure phases in condensed systems and metal-gas systems. 5. S. ?. Uileiko. ceramic matrices. Fiber composites with metallic and Profiled crystals: growth and

prts:
l. An opening speech by Academician A. M. Prokhorov, secretary of the Division of General Physics AstronomY. ;rnd 2. Yu. A. Asip'yan. Basic research directions in the

6. V. A. Tatarchenho. applications.

Four of the reports are summarized below.

V. F. Gantmakher. Low-temperature hinetics aJ conductionelectrons in rnetals and semiconductors. Although the situation in the low-temperature kinetics ol solid-state electron-hole plasmas with a long carrler mean free path has calmed down somewhat since the sensational result of the 1960s, which led to the appearance so-called fermistics, some important of have still occurred in the past decade and a changes half. We can distinguish two basic directions in this research. The first is to study the scattering processes in a solid-state electron-hole plasma. A successful transitlon has been made from measurements of certain average scattering probabilities to measurements of the probabilities for scattering by a phonon or some speeific impurity as functions of the position of the electron on tfie Fermi surface. A transition has been madefrom measurements of the total cross sections for the scattering of electrons by dislocations in metals to measurements of diJferential cross sections. In he reflection of electrons from a surface it has become possible tc measure the dependence of the probabtlity for specular reflection of an electron on the ang{.e incidence and on the position of the electron on of tle tr'ermi surface instead of Leasuring an average dlffusenesscoefficient over all electrons. All this prcgress can be credited to the use of kinetic effects on extremal trajectories-the rf size efiect, the cyclotton resonance, the de Haas-van Alphen effect, the transverse-focusing effect, etc. -to study scattering. leveral new results have been obtained. For example, It has been found that even the exponent in the temperat dependenceof the electro-phonon scattering prota.ur.e 1'tItY depends on the shape of the Fermi surface, so tttat even when a conduction electron is incidenr norloally on the surface of a metal there is a significant Probability for its specular reflection, so that elec8qS Sov. phys. Usp. 26(9), Sept. t9g3

tron-electron scattering can be singled out and measured even in nontransition metals, and so that electrons can be heated to a temperature higher than that of the Iattice not only in semiconductors but also in metals. Experimental techniques have been refined to the point at which it is possible to "see" the conversion of an electron into a hole upon reflection from the interface between a normal metal and a superconducting metal. By studying the magnetoresistance of photoelectrons in germanium cooled to liquid-helium temperature it has been found possible to single out and study the inelastic scattering of these electrons by impurity atoms. A second thrust in the research in the low-temperature kinetics of electron-hole plasmas has been to study new phenomena in electrodynamics. Unfortunately, a brief listing of results in this direction would be far less informative, because each area we would name-the magnetostrictive excitation of sound due to oscillations of the diamagnetic susceptibility of a metal, features of the propagation of helicons at large amplitudes of these oscillations, and the excitation of thermomagnetic and galvonomagnetic waves-is filled .,'rith new phenomena which demand explanation. There is, however, a clear trend in this research. Its center of gravity is gradually shifting toward nonlinear electrodynamics. In metals, nonlinearities result from the effect of the magnetic field of currents on electron trajectories and thus on the conductivity. Although tltis research direction is relatively young, it has already seen much progress and many discoveries. For example, there are current states: macroscopic electromagnetic moments which arise during the bombardment of a metal by an intense electromagnetic rvave as a result of rectification effects in a skin layer. These current states are in many ways reminiscent of ferrolhagnetism: The metal exhibits a hvsteresis and is parti@ 1984 AmericanInstituteof Physics 845

1.80 0038-5670/83/090845-06$0


tioned into domains. Among the nonlinear effects is the effect of a helicon wave on itself, when the magnetic field of the wave combines with an external field to change the helicon dispersion law. We should also mention the appearance of a soliton-like cument distribution in a skin layer at a large amplitude of an alternating field, in which case the skin current is concentrated near a surface at which the alternating magnetic field vanishes, and it moves into the interior

along with this plane; the nonlinear cyclotron resonance, caused by the influence of the magnetic field of a wave on the time required for an electron moving in a cyclotron orbit to traverse a skin layer; and the nonlinear resonanees involving hopping trajectories, which arise from a focusing of electrons which have left the surface of a metal by the exponentially decaying magnetic mi_ crowave field in a skin laver.