Abstract
A new theory for the voltage–current characteristics of high T c DC SQUIDs is developed. The theory is based on an analytical solution of the two-dimensional Fokker–Planck equation, which describes the dynamical behavior of DC SQUIDs in the presence of large thermal noise. For high T c DC SQUIDs, which operate at 77 K, with L>100 pH ( L is the geometrical inductance of the DC SQUID loop), the theory is valid for any values of the reduced inductance β=2 LI C/ Φ 0 and noise parameter Γ=2 πk B T/ I C Φ 0 ( Φ 0 is the flux quantum, I C is the critical current of one Josephson junction, and k B is the Boltzmann constant). Hence, the theory is applicable for most of practical high T c DC SQUIDs with Γ≈0.1–1, β⩾1. We made extensive studies to compare our theory with 70 high T c DC SQUIDs with a sufficiently large range of inductances and critical currents. The results of the comparison are presented.
Published Version
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