Coherent states and their superpositions (cat states) in microwave-induced resistance oscillations

Abstract

We report a novel theoretical approach on the microwave-induced resistance oscillations based on the coherent states of the quantum harmonic oscillator. We first obtain an expression for the coherent states of driven-quantum harmonic oscillators that are used, in the model of microwaveinduced electron orbits, to calculate magnetoresistance under radiation. Thus, we find that the principle of minimum uncertainty of coherent states, involving time and energy, is at the heart of photo-oscillations and zero resistance states. Accordingly, we are able to explain important experimental evidence of this remarkable effect. Such as the physical origin of oscillations, their periodicity with the inverse of the magnetic field, their peculiar minima and maxima positions and the existence of zero resistance states. We apply our theory to the case of ultra-high mobility samples where we appeal to the principle of quantum superposition of coherent states and obtain that Schrodinger cat states (even and odd coherent states) are key to explain magnetoresistance at these extreme mobilities. With them we explain the, experimentally obtained, magnetoresistance resonance peak shift to a magnetic field where the cyclotron frequency equals half the radiation frequency. This effect is similar to the one described in quantum optics as a second harmonic generation process. We also explain the magnetoresistance collapse, that take place in the dark and with light. This effect is known as giant negative magnetoresistance. We generalize our results to study the case of a three-component or triangular Schrodinger cat state.