Weak Antilocalization in a Strongly Disordered Two-Dimensional Semimetal in an HgTe Quantum Well

Weak localization in a highly disordered quantum well Cd_xHg_{1 – x}Te/HgTe/Cd_xHg_{1 – x}Te with a thickness of d = 20 nm is experimentally investigated. An analysis is made of the anomalous positive magnetoresistance (APM) caused by the suppression of the interference correction to the conductivity by a magnetic field on both sides of the charge neutrality point: for a two-dimensional semimetal and for a two-dimensional electronic metal. For the same values of resistivity, the APM peak in a 2D semimetal has a much wider width than in a 2D electron gas. A quantitative comparison of the obtained results with the theory allows, in particular, to conclude that the intensity of carrier transitions between subsystems in the 2D semimetal binary system is maximum near the charge neutrality point, where the concentrations of electrons and holes are close, and decreases as the difference in concentrations increases.