On the role of electron-phonon interaction in the resistance anisotropy of two-dimensional electrons in GaAs heterostructures

A contribution of the electron-phonon interaction into the energy of a unidirectional charge ordered state (stripe phase) of two-dimensional electrons in GaAs heterostructures is analyzed. The dependence of the energy on the direction of the electron density modulation is calculated. It is shown that in electrons layers situated close to the (001) surface the interference between the piezoelectric and the deformation potential interaction causes a preferential orientation of the stripes along the [110] axis.Comment: 9 pages, accepted for publication in Journal of Physics: Condensed Matte

Strong enhancement of third harmonic generation in a double layer graphene system caused by electron-hole pairing

A manifestation of electron-hole pairing in nonlinear electromagnetic response of a double layer graphene system is studied. It is shown that the pairing causes the appearance of a number of peaks in the frequency dependence of the intensity of the third harmonic generation (THG). The highest peak corresponds to \hbar\omega = (2/3)\Delta, where \omega\ is the incident wave frequency, and \Delta\ is the order parameter of the electron-hole pairing. The absolute value of the THG intensity in the systems with electron-hole pairing is in several orders of magnitude greater than the THG intensity in the unpaired state. It is shown that huge enhancement of the THG intensity occurs both in the double monolayer and double bilayer graphene systems.Comment: 7 page

Interaction of quantum Hall systems with waveguide elastic modes

An interaction of non-uniform plane elastic modes of the waveguide type with monolayer and double-layer quantum Hall systems is considered. It is shown, that unlike the case of the surface acoustic wave propagation, the restriction on maximal values of the wave vectors for which the velocity shift can be observed experimentally does not take place for the waveguide modes. In case of study of incompressible fractional quantum Hall states the effect can be used for measuring a dependence of the effective magnetic length on the filling factor and for observing phase transitions in double-layer system under the interlayer distance variationComment: 6 pages, 3 eps figures included, Fig.1 and Fig.3 correcte