arXiv subjects

Vladimir Gasparian

Publications and source records attributed to Vladimir Gasparian.

22 records · Page 2Linked to original sources

arXiv2016

Large diffusion lengths of excitons in perovskite and ${\it TiO_2}$ heterojunction

Solar cells based on organometal halide perovskites have recently become very promising among other materials because of their cost-effective character and improvements in efficiency. Such performance is primarily associated with effective light absorption and large diffusion length of charge carriers. Our paper is devoted to the explanation of large diffusion lengths in these systems. The transport mean free path of charged carriers in a perovskite/${\it TiO_2}$ heterojunction that is an important constituent of the solar cells have been analyzed. Large transport length is explained by the planar diffusion of indirect excitons. Diffusion length of the coupled system increases by several orders compared to single carrier length due to the correlated character of the effective field acting on the exciton.

cond-mat.mtrl-sci↗

arXiv2014

Plasmon Enhanced Faraday Rotation in Thin Films

We have analyzed analytically the Faraday rotation of an electromagnetic wave for magnetoactive thin metallic film with a nanostructured surface profile. Periodical as well as random surface profiles were considered. The plasmon contribution to the Faraday angle was studied. For periodical grating case, we have shown that the maximum of rotation angle is achieved when surface plasmon wave number coincides with one of the wave numbers of the inverse lattice. Enhancement of the Faraday angle at plasmonic band edges is predicted. In the case of random surface profile, it is shown that the diffusion of surface magnetoplasmons gives a dominant contribution to Faraday rotation. Comparison with the experiments is carried out.

cond-mat.mes-hall↗

arXiv2011

Localization Length in Quasi One Dimensional Disordered System Revised

In the weak disordered regime we provide analytical expressions for the electron localization lengths in quasi-one dimensional (Q1D) disordered quantum wire with hard wall and periodic boundary conditions. They are exact up to order $W^2$ ($W$ being the disorder strength) for an arbitrary number of channels. Detailed numerical analysis of the Anderson localization, based on Kubo's formula for conductivity, show excellent agreement with analytical calculations. We establish relationship between various lengths in Q1D systems.

cond-mat.dis-nn↗

arXiv2008

Charge pumping and noise in a one-dimensional wire with weak electron-electron interactions

We consider the adiabatic pumping of charge through a mesoscopic one dimensional wire in the presence of electron-electron interactions. A two-delta potential model is used to describe the wire, which allows to obtain exactly the scattering matrix coefficients, which are renormalized by the interactions. Two periodic drives, shifted one from another, are applied at two locations of the wire in order to drive a current through it in the absence of bias. Analytical expressions are obtained for the pumped charge, current noise, and Fano factor in different regimes. This allows to explore pumping for the whole parameter range of pumping strengths. We show that, working close to a resonance is necessary to have a comfortable window of pumping amplitudes where charge quantization is close to the optimum value: a single electron charge is transferred in one cycle. Interactions can improve the situation, the charge $Q$ is closer to one electron charge and noise is reduced, following a $Q (1-Q)$ behavior, reminiscent of the reduction of noise in quantum wires by $T (1-T)$, where $T$ is the energy transmission coefficient. For large pumping amplitudes, this charge vanishes, noise also decreases but slower than the charge.

cond-mat.mes-hall↗