Ultrasensitive proximity Josephson sensor with kinetic inductance readout

Abstract

We propose a mesoscopic kinetic-inductance radiation detector based on a long superconductor-normal metal-superconductor Josephson junction. The operation of this proximity Josephson sensor relies on large kinetic inductance variations under irradiation due to the exponential temperature dependence of the critical current. Coupled with a dc superconducting quantum interference device readout, the PJS is able to provide a signal to noise (S/N) ratio up to similar to 10(3) in the terahertz regime if operated as calorimeter, while electrical noise equivalent power as low as similar to 7x10(-20) W/root Hz at 200 mK can be achieved in the bolometer operation. The high performance together with the ease of fabrication make this structure attractive as an ultrasensitive cryogenic detector of terahertz electromagnetic radiation. (C) 2008 American Institute of Physics

Non-hysteretic superconducting quantum interference proximity transistor with enhanced responsivity

“…20 For the ideal junction, I C / R À1 N in which R N ¼ ql=A is the normal-state resistance of the SNS junction, q ¼ 1=ð F e 2 DÞ is the island resistivity, A is the island cross section, F is the density of states at the Fermi level in N, and D is the diffusion coefficient of the normal metal. [21][22][23] The hysteresis is suppressed at low temperatures by increasing the Josephson inductance of the junction. 23,24 We achieved this by shrinking the cross section A of the weak-link which leads to an increased normal-state resistance and Josephson inductance.…”

A quantum diffractor for thermal flux

“…heat transport and pave the way for the investigation of more exotic junction geometries 18,26,27 . These might provide tunable temperature diffraction patterns and should represent a powerful tool for tailoring and managing heat currents at the nanoscale 8,[29][30][31] . Besides offering insight into energy transport in quantum nanosystems, our experimental findings set the complementary demonstration of the 'thermal' Josephson effect in weakly coupled superconductors, similarly to what it was done 50 years ago for its 'electric' counterpart.…”

Thermal fluctuations and flux-tunable barrier in proximity Josephson junctions

“…The strong correlation between the measured and the fitted values indicates that the AH theory is somewhat applicable for the flux-tunable proximity junction near Φ = Φ 0 /2, but the effective potential barrier for thermal activation appears to be smaller by about a factor of 5 compared to Eq. (2). As this factor is temperature independent, this "enhanced" fluctuation could not be due to quantum fluctuations, 26 nor due to heating.…”