Conductance in double quantum well systems

Abstract

The object of this paper is to review the electronic conductance in double quantum well systems. These are quantum well structures in which electrons are confined in the z direction by large band gap material barrier layers, yet form a free two-dimensional Fermi gas within the sandwiched low band gap material layers in the x–y plane. Aspects related to the conductance in addition to the research progress made since the inception of such systems are included. While the review focuses on the tunnelling conductance properties of double quantum well devices, the longitudinal conductance is also discussed. Double quantum well systems are a more recent generation of structures whose precursors are the well known double-barrier resonant tunnelling systems. Thus, they have electronic signatures such as negative differential resistance, in addition to resonant tunnelling, whose behaviours depend on the wavefunction coupling between the quantum wells. As such, the barrier which separates the quantum wells can be tailored in order to provide better control of the device’s electronic properties over their single well ancestors.

Unconventional proximity-induced superconductivity in bilayer systems

“…More generally, these and other bilayers systems can be seen as material specializations of the double layer formation of a 2D electronic gas in semiconductor heterostructures, creating an effective double quantum well system. 40,41 In this work we provide a theoretical study of the proximity-induced superconducting state in a general bilayer -superconductor hybrid structure, with results applicable to bilayer systems ranging from TI thin films to generic double quantum well systems.…”

“…Another experimentally relevant tuning is when the Rashba coefficient α → 0, which describes a double quantum well system with no spin-orbit coupling. 41 For no magnetic field all spin-triplet components are then zero and only spin-singlet superconductivity persists. A finite magnetization M generates s-wave spin-triplet m z = 0 pairing, with odd-frequency dependence.…”

On double barrier quantum well conductance effects due to exchange and correlation

“…An important property of the DBRT system is its ability to develop negative differential resistance, which in turn is the basis for practical switches and high frequency oscillators [1,2]. In a recent review [3], we presented results of our calculations for a DBRT system. In that work [3], the voltage dependent current density calculated using the Landauer formula was compared with a Wigner distribution function scheme [4].…”

“…In a recent review [3], we presented results of our calculations for a DBRT system. In that work [3], the voltage dependent current density calculated using the Landauer formula was compared with a Wigner distribution function scheme [4]. The conductance investigation on the DBRT structure thus carried out was a self-consistent one in as far as including electron interactions a la Hartree [5] goes.…”

“…Notwithstanding, the advent of density functional theory (DFT) provides an alternate approach [6,7]. In this paper we incorporate the LDA in our scheme [3] to include the EC potential, . xc u We employ the analytically parametrized xc u of Hedin and Lundqvist [8] which in our present work does not appreciably differ from that of Perdew and Zunger [9].…”