Formation of a Magnetic Pinch in InSb and the Possibility of Population Inversion in the Pinch

A sufficiently strong current supported by an electron-hole plasma in InSb pinches. As the electron-hole gas is compressed by the current's magnetic field, the plasma temperature increases. The strong electron-phonon coupling, however, keeps the plasma temperature below the characteristic temperature of the optical phonons as long as the lattice remains cold. We discuss this early period of the pinch, which includes the initial contraction and some 10^-7 sec thereafter. The collapse of the pinch may be halted by an increase of the plasma pressure caused by the exclusion principle or by the occurrence of impact ionization in the pinch's radial Hall field. An estimate of the particle density in the pinch shows that the conditions for population inversion may be satisfied, hence laser action due to stimulated electron-hole recombination might occur. This effect should influence the development of the pinch decisively.