Quantized adiabatic quantum pumping due to interference

TL;DR

This paper reviews theoretical work showing that quantized charge transfer in mesoscopic devices can occur purely from electron wave interference, deriving a new formula and analyzing specific geometries and surface acoustic wave effects.

Contribution

It introduces a new formula for pumped charge that generalizes existing models and analyzes interference-based quantized pumping in specific device geometries and surface acoustic wave scenarios.

Findings

Derived a new formula for pumped charge Q.

Quantized charge transfer depends on the winding number of the modulation contour.

Surface acoustic wave modulation produces staircase quantized charge behavior.

Abstract

Recent theoretical calculations, demonstrating that quantized charge transfer due to adiabatically modulated potentials in mesoscopic devices can result purely from the interference of the electron wave functions (without invoking electron-electron interactions) are reviewed: (1) A new formula is derived for the pumped charge Q (per period); It reproduces the Brouwer formula without a bias, and also yields the effect of the modulating potential on the Landauer formula in the presence of a bias. (2) For a turnstile geometry, with time-dependent gate voltages V_L(t) and V_R(t), the magnitude and sign of Q are determined by the relative position and orientation of the closed contour traversed by the system in the {V_L-V_R} plane, relative to the transmission resonances in that plane. Integer values of Q (in units of e) are achieved when a transmission peak falls inside the contour, and are given by the winding number of the contour. (3) When the modulating potential is due to surface acoustic waves, Q exhibits a staircase structure, with integer values, reminiscent of experimental observations.