William Mayer

Resistance oscillations of two-dimensional electrons in crossed electric and tilted magnetic fields

Effect of dc electric field on transport of highly mobile 2D electrons is studied in wide GaAs single quantum wells placed in titled magnetic fields. The study shows that in perpendicular magnetic field resistance oscillates due to electric field induced Landau-Zener transitions between quantum levels that corresponds to geometric resonances between cyclotron orbits and periodic modulation of electron density of states. Magnetic field tilt inverts these oscillations. Surprisingly the strongest inverted oscillations are observed at a tilt corresponding to nearly absent modulation of the electron density of states in regime of magnetic breakdown of semiclassical electron orbits. This phenomenon establishes an example of quantum resistance oscillations due to Landau quantization, which occur in electron systems with a constant density of states.

Positive quantum magnetoresistance in tilted magnetic field

Transport properties of highly mobile 2D electrons are studied in symmetric GaAs quantum wells placed in titled magnetic fields. Quantum positive magnetoresistance (QPMR) is observed in magnetic fields perpendicular to the 2D layer. Application of in-plane magnetic field produces a dramatic decrease of the QPMR. This decrease correlates strongly with the reduction of the amplitude of Shubnikov de Haas resistance oscillations due to modification of the electron spectrum via enhanced Zeeman splitting. Surprisingly no quantization of the spectrum is detected when the Zeeman energy exceeds the half of the cyclotron energy suggesting an abrupt transformation of the electron dynamics. Observed angular evolution of QPMR implies strong mixing between spin subbands. Theoretical estimations indicate that in the presence of spin-orbital interaction the elastic impurity scattering provides significant contribution to the spin mixing in GaAs quantum wells at high filling factors.

Magnetointersubband resistance oscillations in GaAs quantum wells placed in a tilted magnetic field

The magnetotransport of highly mobile 2D electrons in wide GaAs single quantum wells with three populated subbands placed in titled magnetic fields is studied. The bottoms of the lower two subbands have nearly the same energy while the bottom of the third subband has a much higher energy (

Microwave nonlinear response of oxide superconducting films in the Berezinskii-Kosterlitz-Thouless state

E_1\approx E_2<<E_3

Frequency dispersion of nonlinear response of thin superconducting films in the Berezinskii-Kosterlitz-Thouless state

). At zero in-plane magnetic fields magneto-intersubband oscillations (MISO) between the

Dynamics of quantal heating in electron systems with discrete spectra

i^{th}

Quantum electron transport in magnetically entangled subbands

and

Quantum electron lifetime in GaAs quantum wells with three populated subbands

j^{th}

Transport Properties of Near Surface InAs Two-dimensional Heterostructures.

subbands are observed and obey the relation

Superconducting proximity effect in epitaxial Al-InAs heterostructures.

\Delta_{ij}=E_j-E_i=k\cdot\hbar\omega_c