Efficiency of the SQUID ratchet driven by external current
نویسنده
چکیده
We study theoretically the efficiency of an asymmetric superconducting quantum interference device (SQUID)which is constructed as a loopwith three capacitively and resistively shunted Josephson junctions. Two junctions are placed in series in one arm and the remaining one is located in the other arm. The SQUID is threaded by an externalmagnetic flux and driven by an external current of both constant (dc) and time periodic (ac) components. This system acts as a nonequilibrium ratchet for the dc voltage across the SQUIDwith the external current as a source of energy.We analyze the power delivered by the external current andfind that it strongly depends on thermal noise and the external magneticflux.We explore a space of the systemparameters to reveal a set forwhich the SQUID efficiency is globallymaximal.We detect the intriguing feature of the thermal noise enhanced efficiency and showhow the efficiency of the device can be tuned by tailoring the externalmagnetic flux.
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