Spin-polarized transport through a quantum point contact in strongly quantizing magnetic fields: mimicking the 0.7 scenario

• Published in: Journal of physics. Condensed matter Vol. 18; no. 12; pp. 3277 - 3284
• Main Authors: Shailos, A, Bird, J P, Lilly, M P, Reno, J L, Simmons, J A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 29.03.2006; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic transport in condensed matter; Exact sciences and technology; Physics; Spin polarized transport; Quantum magnetic field; Spin polarized transport; Quantum dots; Two-level systems; Magnetic field effects; Landau levels; Spin state
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/18/12/009

We study the influence of a normal magnetic field on the 0.7 feature exhibited by quantum point contacts (QPCs). The magnetic field is used to induce the formation of edge states whose spin splitting and spatial separation can be varied directly via the applied field. By appropriate control of the gate voltage, the QPC can be configured so that its conductance is determined by the two spin-resolved edge states of the lowest Landau level, mimicking the two-channel picture that has been suggested in discussions of the 0.7 feature. Under these conditions, a clear 0.7 feature is only observed at weak magnetic fields, where any spin gap is small and the two edge states are strongly overlapping. A similar feature is also seen at high magnetic fields, but only once the temperature is increased such that the thermal energy is comparable to the size of the spin gap. The connection of these results to the processes that lead to the 0.7 feature is discussed.