Beyond-ballistic transport in an open quantum ring

Abstract

In an open quantum ring (OQR), an asymmetric ring-to-electrode configuration, where the upper and lower arms have unequal lengths, generates antiresonances in the junction transmission spectrum around the doubly degenerate eigenenergies of the isolated ring Hamiltonian. The asymmetric OQR also gives rise to a net circular current transmission within the ring, specifically around these doubly degenerate eigenenergies. We investigate the system-size scaling properties of the transmission within the ring and the overall junction transmission of an OQR. Ballistic transport refers to the unhindered flow of charge carriers within a conductor, where transmission is independent of the system size. Here, we find beyond-ballistic behavior, characterized by an anomalous increase of the transmission with increasing system size, near both the degenerate and non-degenerate eigenenergies of the ring Hamiltonian, depending on the ring-to-electrode configuration. This phenomenon is unique to OQRs and is associated with the quantum interference effect between two counter-propagating electronic waves with nearly equal and opposite momenta. Consequently, there is no equivalent phenomenon in open quantum junctions with linear conductors.

13 pages, 14 figures (Accepted for publication in APS Open Science)