Study of quantum decays of metastable current states in RF SQUIDs

Journal Article · Fri Feb 01 04:00:00 EST 1985 · Sov. J. Low Temp. Phys. (Engl. Transl.); (United States)

OSTI ID:5933844

Dmitrenko, I M; Khlus, V A; Tsoi, G M; Shnyrkov, V I

The mechanisms of the decay of metastable current states in the superconducting loop of an RF SQUID in the hysteresis state are studied. Clamped point contacts are used as the Josephson weak link. The first derivative of the radio-frequency IVC dV/sub T//dI/sub R/F, which gives the dependence of the decay probability density on the amplitude of the oscillations of the magnetic flux in the ring, was measured experimentally. Studies of the temperature dependence of the width of the probability distribution in the interval from 4.2 to 0.5 K show that for most high-resistance Nb--Nb, Nb--Ag--Nb contacts the quantum mechanisms of decay become dominant at a temperature of the order of 2 K. The experimentally measured parameters of the decay probability distribution in the quantum limit are compared with the theoretical values calculated based on the theory of macroscopic quantum tunneling in the limit of strong and weak dissipation. The experimental magnitude of the width of the probability density as well as the characteristic quantum temperature exceed the theoretical values, which can be explained by the deviation of the current-phase dependence of the contact from a sinusoidal dependence. In addition, some contacts apparently correspond to the case of an intermediate magnitude of dissipation. When the frequency of the RF oscillations changed from 30 to 6 MHz, the width of the distribution remained unchanged, which follows from the theory of quantum tunneling decay of the metastable current state in the loop in the limit of strong damping.

• Research Organization: Physicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Kharkov
• OSTI ID: 5933844
• Journal Information: Sov. J. Low Temp. Phys. (Engl. Transl.); (United States), Journal Name: Sov. J. Low Temp. Phys. (Engl. Transl.); (United States) Vol. 11:2; ISSN SJLPD
• Country of Publication: United States
• Language: English

Related Subjects

640450* -- Fluid Physics-- Superfluidity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
DENSITY
DISPERSIONS
ELASTICITY
EVEN-EVEN NUCLEI
FLUIDS
GLASS
HELIUM 4
HELIUM II
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MECHANICAL PROPERTIES
MOMENT OF INERTIA
NUCLEI
PHYSICAL PROPERTIES
POROSITY
QUANTUM FLUIDS
STABLE ISOTOPES
SUPERFLUIDITY
SUSPENSIONS
TEMPERATURE DEPENDENCE
TENSILE PROPERTIES
VOIDS
VYCOR