Bogolon-mediated electron capture by impurities in hybrid Bose-Fermi systems

We investigate the processes of electron capture by a Coulomb impurity center residing in a hybrid system consisting of spatially separated two-dimensional layers of electron and Bose-condensed dipolar exciton gases coupled via the Coulomb forces. We calculate the probability of the electron capture accompanied by the emission of a single Bogoliubov excitation (bogolon), similar to regular phonon-mediated scattering in solids. Further, we study the electron capture mediated by the emission of a pair of bogolons in a single capture event and show that these processes not only should be treated in the same order of the perturbation theory, but also they give more important contribution than single bogolon-mediated capture, in contrast with regular phonon scattering.Comment: Paper: 5 pages, 4 figure

Numerical Investigations on Changes of the Main Shear Plane while Broaching

AbstractThe quality of broached components can be influenced by different factors, such as am-bient temperatures, human factors or vibrations of the machine structure induced by process-machine-interactions. These vibrations are normally initiated by changing pro-cess forces, which are mainly caused by cutting thickness or rake angle variations. Broached components are produced within one motion of the broach along the surface of the work piece, where multiple teeth in a row are in contact. The variation of the cut- ting thickness results from a wavy profile on the surface generated by the previous cut-ting process or the previous tooth. When the cutting thickness changes during the process, the rake angle varies, too. In some further published works, the changing cutting thickness and the changing rake angle during broaching were investigated by means of machining simulations with the result that the process forces are still adjusting after the cutting thickness and the rake angle have already reached a stable value. The adjustment of the shear plane on the new cutting conditions is mentioned as the main reason. This paper presents some deeper investigations on this effect. Therefore, 2D machining simulations for different cutting thicknesses and cutting velocities are performed. The investigations show tendencies for the still adjusting shear plane after changing the cutting thickness or the rake angle during the cutting process. Finally, the simulation results are validated with experimentally observed data

Optically induced resonant tunneling of electrons in nanostructures

We developed the theory of elastic electron tunneling through a potential barrier driven by a strong high-frequency electromagnetic field. It is demonstrated that the driven barrier can be considered as a stationary two-barrier potential which contains the quasi-stationary electron states confined between these two barriers. When the energy of an incident electron coincides with the energy of the quasi-stationary state, the driven barrier becomes fully transparent for the electron (the resonant tunneling). The developed theory is applied to describe electron transport through a quantum point contact irradiated by an electromagnetic wave.Comment: Published versio

Elementary excitations in the hybrid Bose-Fermi system induced by circularly polarized light in a two-dimensional gas of charge carriers with different masses

We developed a theory describing elementary excitations in the Bose-Fermi system induced by circularly polarized light in a two-dimensional (2D) gas of charge carriers with different masses. In such a hybrid system, the Fermi subsystem is a degenerate Fermi gas, whereas the Bose subsystem is a condensate of the light-induced composite bosons consisting of two fermions (electrons or holes) with different effective masses. The interaction of the single-particle excitations and the collective excitations (plasmons) in the Fermi subsystem with the Bogoliubov collective modes (bogolons) in the Bose subsystem is analyzed. The renormalization and damping (lifetime) of the excitations are calculated, and the possibility of their experimental observation is discussed. The developed theory can be applied to describe 2D condensed-matter structures containing charge carriers with different effective masses, including transition metal dichalcogenide monolayers and semiconductor quantum wells.Comment: Published versio