59 research outputs found
On-demand population of Andreev levels by their ionization in the presence of Coulomb blockade
A mechanism to deterministically prepare a nanowire Josephson junction in an
odd parity state is proposed. The mechanism involves population of two Andreev
levels by a resonant microwave drive breaking a Cooper pair, and a subsequent
ionization of one of the levels by the same drive. Robust preparation of the
odd state is allowed by a residual Coulomb repulsion in the junction. A similar
resonant process can also be used to prepare the junction in the even state.
Our theory explains a recent experiment [J. J. Wesdorp, et al., Phys. Rev.
Lett. 131, 117001 (2023)]
Energy spectrum and current-phase relation of a nanowire Josephson junction close to the topological transition
A semiconducting nanowire proximitized by an -wave superconductor can be
tuned into a topological state by an applied magnetic field. This quantum phase
transition is marked by the emergence of Majorana zero modes at the ends of the
wire. The fusion of Majorana modes at a junction between two nanowires results
in a -periodic Josephson effect. We elucidate how the -periodicity
arises across the topological phase transition in a highly-transparent short
nanowire junction. Owing to a high transmission coefficient, Majorana zero
modes coming from different wires are strongly coupled, with an energy scale
set by the proximity-induced, field-independent pairing potential. At the same
time, the topological spectral gap---defined by competition between
superconducting correlations and Zeeman splitting---becomes narrow in the
vicinity of the transition point. The resulting hybridization of the fused
Majorana states with the spectral continuum strongly affects the electron
density of states at the junction and its Josephson energy. We study the
manifestations of this hybridization in the energy spectrum and phase
dependence of the Josephson current. We pinpoint the experimentally observable
signatures of the topological phase transition, focusing on junctions with weak
backscattering.Comment: 26 pages, 11 figure
- …