Abstract
We introduce a design of electrically isolated “floating” bilayer GaAs quantum wells (QW), in which application of a large gating voltage controllably and highly reproducibly induces charges that remain trapped in the bilayer after removal of the gating voltage. At smaller gate voltages, the bilayer is fully electrically isolated from external electrodes by thick insulating barriers. This design permits full control of the total and differential densities of two coupled 2D electron systems. The floating bilayer design provides a unique approach for studying systems inaccessible by simple transport measurements. It also provides the ability to measure the charge transfer between the layers, even when the in-plane resistivities of the 2D systems diverge. We measure the capacitance and inter-layer tunneling spectra of the QW bilayer with independent control of the top and bottom layer electron densities. Our measurements display strongly enhanced inter-layer tunneling current at vT=1, a signature of exciton condensation of a strongly interlayer-correlated bilayer system. With fully tunable densities of individual layers, the floating bilayer QW system provides a versatile platform to access previously unavailable information on the quantum phases in electron bilayer systems.
Highlights
The exciton condensate is an interlayer-coherent phase that shows dramatic macroscopic quantum phenomena, such as Josephson-like interlayer tunneling, quasiparticle tunneling, and perfect Coulomb drag, as observed in GaAs quantum wells (QW) bilayers and graphene bilayers.1,11–15 The interlayer interaction has an energy scale of Ec
We introduce a design of electrically isolated “floating” bilayer GaAs quantum wells (QW), in which application of a large gating voltage controllably and highly reproducibly induces charges that remain trapped in the bilayer after removal of the gating voltage
In most previous experiments with bilayer QWs, charge carriers were induced by doping from top and bottom of the layers and one eventually needed to make Ohmic contacts for transport measurements
Summary
The exciton condensate is an interlayer-coherent phase that shows dramatic macroscopic quantum phenomena, such as Josephson-like interlayer tunneling, quasiparticle tunneling, and perfect Coulomb drag, as observed in GaAs quantum wells (QW) bilayers and graphene bilayers.1,11–15 The interlayer interaction has an energy scale of Ec. We use a contactless pulsed tunneling method, applying a sudden voltage step from external electrodes and remotely sense the electric field emanating from charges moving in-between layers via the HEMT amplifiers to measure interlayer tunneling spectra.19,20
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.