Long-wavelength excitations in the Wigner crystal in strong magnetic fields

Excitation spectra in the Wigner crystal in strong magnetic fields have been investigated and special attention has been paid to the effects of finite shear stress, which is absent in magnetised plasmas. It is shown that the velocity of the shear mode is strongly dependent on the strength of the magnetic field, and can be made comparable to the velocity of ultrasound in a semiconductor. It is predicted that when these two velocities become equal to each other in a highly compensated semiconductor such as n-type InSb, resonant absorption of the ultrasound occurs through the piezoelectric interaction. This absorption should provide clear experimental evidence for the Wigner crystallisation.