Charge rearrangement and screening in a quantum point contact

Abstract

Compressibility measurements, sensitive to charge rearrangements, are performed on a quantum point contact (QPC). Screening due to mobile charges in the QPC is quantitatively measured, using a second point contact to detect the screened electrical potential. These measurements are performed from pinch-off through the opening of the first few modes in the QPC. While the measured signal closely matches a Thomas-Fermi-Poisson prediction, deviations from the classical behavior, in the form of additional dips, are apparent near the openings of the different modes, with the largest dip at the opening of the first mode. Density functional calculations attribute the first dip to exchange interactions. The other dips reflect the diverging density of states at the opening of each one-dimensional mode, which affects both kinetic and exchange contributions to the energy.

6 pages, 5 figures. Published in PRL. Supplementary Information is included. Changes: Two references and journal reference added

References in corpus (7)

• The Low-Temperature Fate of the 0.7 Structure in a Point Contact: A Kondo-like Correlated State in an Open System
• Kondo model for the "0.7 anomaly" in transport through a quantum point contact
• The microscopic nature of localization in the quantum Hall effect
• Magnetic impurity formation in quantum point contacts
• Conductance of a quantum wire at low electron density
• Local moment formation in quantum point contacts
• Excited-state spectroscopy on a nearly-closed quantum dot via charge detection

Cited by in corpus (9)

• What lurks below the last plateau: Experimental studies of the 0.7 x 2e^2/h conductance anomaly in one-dimensional systems
• Inelastic Backaction due to Quantum Point Contact Charge Fluctuations
• Compressibility measurements of quasi-one-dimensional quantum wires
• Interacting electrodynamics of short coherent conductors in quantum circuits
• Transconductance and effective Landé factors for quantum point contacts: spin-orbit coupling and interaction effects
• Temperature Modulation of the Transmission Barrier in Quantum Point Contacts
• Dephasing in a quantum dot coupled to a quantum point contact
• Magnetic Splitting of the Zero Bias Peak in a Quantum Point Contact with a Variable Aspect Ratio
• Dispersive Gate Sensing the Quantum Capacitance of a Point Contact