57 research outputs found
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
Short-wavelength out-of-band EUV emission from Sn laser-produced plasma
We present the results of spectroscopic measurements in the extreme
ultraviolet (EUV) regime (7-17 nm) of molten tin microdroplets illuminated by a
high-intensity 3-J, 60-ns Nd:YAG laser pulse. The strong 13.5 nm emission from
this laser-produced plasma is of relevance for next-generation nanolithography
machines. Here, we focus on the shorter wavelength features between 7 and 12 nm
which have so far remained poorly investigated despite their diagnostic
relevance. Using flexible atomic code calculations and local thermodynamic
equilibrium arguments, we show that the line features in this region of the
spectrum can be explained by transitions from high-lying configurations within
the Sn-Sn ions. The dominant transitions for all ions but
Sn are found to be electric-dipole transitions towards the =4 ground
state from the core-excited configuration in which a 4 electron is promoted
to the 5 sub-shell. Our results resolve some long-standing spectroscopic
issues and provide reliable charge state identification for Sn laser-produced
plasma, which could be employed as a useful tool for diagnostic purposes.Comment: 11 pages, 4 figure
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