Nonadiabatic charge pumping by oscillating potentials in one dimension: results for infinite system and finite ring

Soori, Abhiram ; Sen, Diptiman (2010) Nonadiabatic charge pumping by oscillating potentials in one dimension: results for infinite system and finite ring Physical Review B: Condensed Matter and Materials Physics, 82 (11). 115432_1-115432_15. ISSN 1098-0121

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Official URL: http://prb.aps.org/abstract/PRB/v82/i11/e115432

Related URL: http://dx.doi.org/10.1103/PhysRevB.82.115432

Abstract

We study charge pumping when a combination of static potentials and potentials oscillating with a time period T is applied in a one-dimensional system of noninteracting electrons. We consider both an infinite system using the Dirac equation in the continuum approximation and a periodic ring with a finite number of sites using the tight-binding model. The infinite system is taken to be coupled to reservoirs on the two sides which are at the same chemical potential and temperature. We consider a model in which oscillating potentials help the electrons to access a transmission resonance produced by the static potentials and show that nonadiabatic pumping violates the simple sin ϕ rule which is obeyed by adiabatic two-site pumping. For the ring, we do not introduce any reservoirs, and we present a method for calculating the current averaged over an infinite time using the time evolution operator U(T) assuming a purely Hamiltonian evolution. We analytically show that the averaged current is zero if the Hamiltonian is real and time-reversal invariant. Numerical studies indicate another interesting result, namely, that the integrated current is zero for any time dependence of the potential if it is applied to only one site. Finally we study the effects of pumping at two sites on a ring at resonant and nonresonant frequencies, and show that the pumped current has different dependences on the pumping amplitude in the two cases.

Item Type:Article
Source:Copyright of this article belongs to The American Physical Society.
ID Code:45527
Deposited On:28 Jun 2011 05:48
Last Modified:18 May 2016 01:46

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