Magnetic susceptibility measurements in HgTe quantum wells in a perpendicular magnetic field

The magnetic susceptibility of two-dimensional systems in the limit of low fields can hardly be detected by magnetometric measurements because it is difficult to separate the contributions from the substrate and two-dimensional gas for the magnetization not oscillating with the field. The derivative of the magnetization with respect to the carrier density in two-dimensional systems in narrow (thickness $<7$ nm) HgTe quantum wells has been measured in this work by means of the modulation of the chemical potential by a magnetic field perpendicular to the system plane. It was previously established that the spectrum of the valence band of such quantum wells contains not only easy Dirac states in the center of the Brillouin zone but also heavy hole valleys with maxima shifted from the center in the $[33\bar{1}]$ direction. It has been found that the magnetic susceptibility drops sharply as the Fermi level leaves these heavy valleys with the addition of electrons to the system. This behavior can be interpreted either as the weakening of paramagnetism or as the enhancement of diamagnetism. The estimates obtained show that the observed effect is due primarily to the paramagnetism of states in the heavy valleys of the valence band.