Hall magnetoresistivity response under Microwave excitation revisited

We theoretically analyzed the microwave-induced modification of the Hall magnetoresistivity in high mobility two-dimensional electron systems. These systems present diagonal magnetoresistivity oscillations and zero-resistance states when are subjected to microwave radiation. The most surprising modification of the Hall magnetoresistivity is a periodic reduction which correlates with a periodic increase in the diagonal resistivity. We present a model that explains the experimental results considering that radiation affects directly only the diagonal resistivity and the observed Hall resistivity changes are coming from the tensor relationship between both of them.Comment: 3 pages, 2 figure

Magnetoresistivity Modulated Response in Bichromatic Microwave Irradiated Two Dimensional Electron Systems

We analyze the effect of bichromatic microwave irradiation on the magnetoresistivity of a two dimensional electron system. We follow the model of microwave driven Larmor orbits in a regime where two different microwave lights with different frequencies are illuminating the sample ($w_{1}$ and $w_{2}$). Our calculated results demonstrate that now the electronic orbit centers are driven by the superposition of two harmonic oscillatory movements with the frequencies of the microwave sources. As a result the magnetoresisitivity response presents modulated pulses in the amplitude with a frequency of $\frac{w_{1}-w_{2}}{2}$, whereas the main response oscillates with $\frac{w_{1}+w_{2}}{2}$.Comment: 4 pages, 3 figures Accepted in Applied Physics Letter

From zero resistance states to absolute negative conductivity in microwave irradiated 2D electron systems

Recent experimental results regarding a 2D electron gas subjected to microwave radiation reveal that magnetoresistivity, apart from presenting oscillations and zero resistance states, can evolve to negative values at minima. In other words, the current can evolve from flowing with no dissipation, to flow in the opposite direction of the dc bias applied. Here we present a theoretical model in which the existence of radiation-induced absolute negative conductivity is analyzed. Our model explains the transition from zero resistance states to absolute negative conductivity in terms of multiphoton assisted electron scattering due to charged impurities. It shows as well, how this transition can be driven by tuning microwave frequency and intensity. Then it opens the possibility of controlling the electron Larmor orbits dynamics (magnetoconductivity) in microwave driven nanodevices. The analysis of zero resistance states is therefore promising because new optical and transport properties in nanodevices will be expected.Comment: 5 pages and 4 figure

Ferromagnetically coupled magnetic impurities in a quantum point contact

We investigate the ground and excited states of interacting electrons in a quantum point contact using exact diagonalization method. We find that strongly localized states in the point contact appear when a new conductance channel opens due to momentum mismatch. These localized states form magnetic impurity states which are stable in a finite regime of chemical potential and excitation energy. Interestingly, these magnetic impurities have ferromagnetic coupling, which shed light on the experimentally observed puzzling coexistence of Kondo correlation and spin filtering in a quantum point contact