Magnetotunneling spectroscopy with the field perpendicular to the tunneling direction of the transverseXelectrons in GaAs/AlAs double-barrier structures under hydrostatic pressure

We have measured the effect of in-plane magnetic field on tunneling resonances between transverse X states in GaAs/AlAs double-barrier structures under high hydrostatic pressure. Current-voltage and conductance-voltage measurements performed at pressures just beyond the type-II transition, and at fields up to 15 T, reveal clear field dependences of resonances originating from the Xₜ(1)→Xₜ(1) and Xₜ(1)→Xₜ(2) tunneling processes. Their behavior is consistent with a Lorenz force analysis, and therefore probes the in-plane electron dispersion around the X minima. Differences between measurements with the magnetic field oriented parallel to the [100] and [110] crystal axes reflect the anisotropy of the X minima, a first analysis indicating that the field dependence is dominated by the two Xₜ minima with large wave vectors perpendicular to the magnetic-field direction. In support of this, Schr\"odinger-Poisson modeling of the shift in bias position of the Xₜ(1)→Xₜ(2) resonance provides a value for the effective mass parallel to the Lorenz in-plane momentum vector which is consistent with the heavy principal effective mass of the X minima.