Pauli blocking factors in quantum pumps

Abstract

We investigate the Pauli blocking factor in quantum pumps using Floquet formalism. Even though the time dependent potentials in quantum pumping can not only cause inelastic scatterings but also break the micro-reversibility, i.e. $T^+(E',E) \neq T^-(E,E')$, the Pauli blocking factor is unnecessary when the scattering process through the scatterer is coherent. The well defined scattering states extending from one reservoir to the others form a complete non-orthogonal set. Regardless of the non-orthogonality one can obtain the pumped currents using the field operator formalism. The current expression finally obtained do not contain Pauli blocking factor.Comment: 4 pages, 2 figure

Numerical study of parametric pumping current in mesoscopic systems in the presence of a magnetic field

“…The electron pump is driven by periodical modulation of potentials which share the same spatial coordinates with the confining potentials which preserve reflection symmetry of the system. Most of our numerical results agree with the conclusions from Floquet scattering theory 28,29 , except for the general inversion symmetry (GIV) ( setup f in Fig.1 ). In contrast with the theoretical prediction that the adiabatic pumped current I ad ≈ 0 for this spatial symmetry, our numerical calculation shows that the pumped current is finite and further investigation reveals that there is an approximate symmetry relation of the current as setup e at small magnetic field, which is the experimental setup 8 .…”

“…Six spatial symmetries studied in Ref. 29 are considered, both at the adiabatic and non-adiabatic cases, which are instantaneous up-down (IUD), left-right (ILR), and inversion symmetries (IIV) and the corresponding non-instantaneous/general up-down (GUD), left-right (GLR), and inversion symmetries (GIV), respectively (see Fig.1). The electron pump is driven by periodical modulation of potentials which share the same spatial coordinates with the confining potentials which preserve reflection symmetry of the system.…”

Nonmagnetic control of spin flow: Generation of pure spin current in a Rashba-Dresselhaus quantum channel

“…28, 29 The spin current and charge current at lead R are defined as I Secondly, when certain amount of spin current is pumped out at lead R, there should be equal amount of spin current with opposite polarization pumped out at lead L. Furthermore, if this symmetry is combined with current conservation condition, spin current formula can be simplified to a more convenient form in calculation:…”

Floquet Formalism of Quantum Pumps

“…We derive the current using these scattering states. The time dependent electron field operator can be obtained in the following form [17,18,19] …”

“…These symmetries are only applied to the time independent part of the scattering potential, which is V n (r) in Eq. (25), with an arbitrary φ, so that they are not necessarily kept intact during the pumping cycle [37].…”