[institut] SCL seminar (povodom izbora u zvanje), Veljko Jankovic, petak 27. februar u 14:00

[Nenad Vukmirović]

Поштоване колегинице и колеге,

Позивам вас на семинар Лабораторије за примену рачунара у науци који ће 
у петак 27. фебруара у 14:00 у читаоници "Др Драган Поповић" Института 
за физику одржати Вељко Јанковић (Лабораторија за примену рачунара у 
науци, Институт за физику Београд) поводом предстојећег избора у звање 
истраживач сарадник. Наслов семинара је:

Nonequilibrium High-Frequency Conductivity in Materials with Localized 
Electronic States

Abstract:

A broad range of disordered materials contain electronic states that are 
spatially well localized. Usual approaches to simulation of ac 
conductivity of these materials rely on Kubo's formula which expresses 
the ac conductivity in terms of the mean square displacement of a 
diffusing carrier. Such approaches therefore assume that carriers are in 
equilibrium and that they are only slightly perturbed by external 
alternating electric field. In [1] we obtain the expression for the 
optical conductivity in a material with localized electronic states and 
weak electron-phonon or electron-impurity interaction which is valid for 
any nonequilibirum state of the electronic subsystem prior to the action 
of electric field. Particularly, in the case of incoherent 
nonequilibrium state of the electronic subsystem, the optical 
conductivity is entirely expressed in terms of the positions of 
electronic states, their nonequilibrium populations, and Fermi's golden 
rule transition probabilities between the states. The same mathematical 
form of the expression is valid both in the case of electron-phonon and 
electron-impurity interaction. Moreover, our result for the 
nonequilibrium optical conductivity has the same form as the expressions 
previously obtained for the case of equilibrium. Our results are 
expected to be valid at sufficiently high frequencies, such that the 
period of the electric field is much smaller than the carrier relaxation 
time. We apply the derived expressions to two model systems, a simple 
one-dimensional Gaussian disorder model and the model of a realistic 
three-dimensional organic polymer material obtained using previously 
developed multiscale methodology. We note that the simple 
one-dimensional model captures the essential features of the mobility 
spectrum of a more realistic system.

[1] V. Janković and N. Vukmirović, Phys. Rev. B 90, 224201 (2014).

Срдачан поздрав,

-- 
Др Ненад Вукмировић,
Виши научни сарадник,
Лабораторија за примену рачунара у науци,
Институт за физику Београд,
Србија.
URL: http://www.scl.rs/nenad

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