Effect of leads and quantum fluctuations in small superconducting tunnel junctions

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1990

OSTI ID:5300552

Johnson, Jr, A T

For more than 20 years, experimenters have used the resistively-and-capacitively-shunted-junction (RCSJ) model to predict the dynamics of Josephson junctions. Using electron-beam lithography and dilution refrigeration the author made samples as small as 0.04 {mu}m{sup 2} and measured their properties at temperatures from 20 m{Kappa} to 6 {Kappa}. The ratio of the charging energy E{sub C} {equivalent to}e{sup 2}/2C to the Josephson coupling energy E{sub J} varied from 0.01 to 6. When R{sub n} {gt} 1{Kappa}{Omega}, and E{sub C}/E{sub J} is small, the devices act like the conventional ones of earlier investigations. As r{sub n} and E{sub C}/E{sub J} increase, striking new behavior was observed. First, an anomalous resistance R{sub O} appears on the low-voltage branch of the still-hysteretic current-voltage characteristic (IVC), inconsistent with the RCSJ model, but allowed by a mode that contains the leads. Second, the retrapping current I{sub r} attains a non-zero, plateau minimum as T {yields} O, in contrast to the e{sup {minus}{Delta}/k{Tau}} dependence predicted by the RCSJ model. To explain this, the authors must add to the model both the leads and the onset of pair-breaking quasiparticle tunneling at V = 2{Delta}/e. Analog simulations and an analytic estimation procedure for I{sub r} that agree quantitatively with the data are presented.

• Research Organization: Harvard Univ., Boston, MA (United States)
• OSTI ID: 5300552
• Country of Publication: United States
• Language: English

Related Subjects

665412* -- Superconducting Devices-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
DYNAMICS
ELECTRICAL PROPERTIES
FABRICATION
JOSEPHSON JUNCTIONS
JUNCTIONS
MATHEMATICAL MODELS
MECHANICS
PHYSICAL PROPERTIES
SIMULATION
SUPERCONDUCTING JUNCTIONS
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K