Resonant-acceptor-bound magnetic polarons in the zero-band-gap semimagnetic semiconductor Hg1−xMnxTe

Abstract

Far-infrared magneto-optical studies of zero-band-gap p-type ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Mn}}_{\mathit{x}}$Te (x=0.065 and 0.070) for temperatures down to 1.6 K and magnetic fields up to 9 T are presented. Transitions of the resonant-acceptor state to the uppermost heavy-hole level are identified by the selection rules, temperature-dependent exchange effect, and k⋅p Landau-level calculations. A remarkable shift of the resonance field with increasing temperature is observed, which is attributed to the strong sp-d exchange interaction. The plot of the resonance energy as a function of calculated magnetization, followed by a linear extrapolation using a least-squares fit, yields the negative zero-field resonant-acceptor energy whose magnitude increases as temperature is lowered and saturated above T∼16 K. This feature indicates the possible formation of resonant-acceptor-bound magnetic polarons (RABMP’s) in the ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Mn}}_{\mathit{x}}$Te at low temperature and low external magnetic field. The zero-field binding energies of RABMP’s are found to be ≃3.5 meV (3.8 meV), in the limit of zero temperature for x=0.065 (x=0.070).