Terahertz Shapiro steps in high temperature SNS Josephson junctions

Journal Article · Fri Apr 01 00:00:00 EST 1994 · IEEE Transactions on Microwave Theory and Techniques (Institute of Electrical and Electronics Engineers); (United States)

DOI:https://doi.org/10.1109/22.285085· OSTI ID:7295808

Rosenthal, P A ^[1]; Grossman, E N ^[2]

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1. Advanced Fuel Research Inc., East Hartford, CT (United States)
2. National Inst. of Standards and Technology, Boulder, CO (United States). Electromagnetic Technology Div.

The authors have studied the far infrared behavior of high-T[sub c] superconductor-normal metal-superconductor (SNS) microbridges with T[sub c] > 85 K and critical current-resistance products (I[sub c]R[sub N]) as high as 10 mV at 4 K. These are the highest I[sub c]R[sub N] products reported to date for microfabricated Josephson junctions of any material. The junctions were integrated at the feeds of planar log-periodic antennas made from Au thin films. The junctions had dc normal state resistances R[sub N] between 6 and 38 [Omega], reasonably well matched to the antenna's estimated RF impedance of 53 [Omega]. Far infrared laser radiation at 404, 760, and 992 GHz induced distinct Shapiro steps (i.e. constant voltage steps at voltages n(h[integral]/2e), n = 1,2,...) in the current voltage characteristics as well as modulation of the critical current. Steps were observed at voltages up to 17 mV and 6 mV, at temperatures of 9 K and 57 K, respectively. This corresponds to maximum Josephson oscillation frequencies of 8 and 3 THz at these temperatures. These are the first far infrared measurements performed on high T[sub c] junctions. Measurements of the power, frequency, and temperature dependence of the Shapiro steps are presented and discussed in the context of a resistively and capacitively shunted junction (RCSJ) model. A value of 4.5 fF for the junction capacitance is inferred from the hysteresis of the slightly underdamped current-voltage characteristics.

• OSTI ID: 7295808
• Journal Information: IEEE Transactions on Microwave Theory and Techniques (Institute of Electrical and Electronics Engineers); (United States), Vol. 42:4 Pt2; ISSN 0018-9480
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
JOSEPHSON JUNCTIONS
ELECTRICAL PROPERTIES
EXPERIMENTAL DATA
FREQUENCY DEPENDENCE
GOLD
HIGH-TC SUPERCONDUCTORS
MATHEMATICAL MODELS
DATA
ELEMENTS
INFORMATION
JUNCTIONS
METALS
NUMERICAL DATA
PHYSICAL PROPERTIES
SUPERCONDUCTING JUNCTIONS
SUPERCONDUCTORS
TRANSITION ELEMENTS
665412* - Superconducting Devices- (1992-)