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Modern Physics Letters B c ○ World Scientific Publishing Company ON A POSSIBILITY TO MEASURE THERMOELECTRIC POWER IN SNS STRUCTURES

By B. J. Ahmedov

Abstract

Two dissimilar Josephson junctions, which are connected to a heater can act as precise batteries. Because of the difference in thermoelectric power of these batteries, circuit with two dissimilar batteries, under heat flow ∆T ∼ 10 −5 K would have a net EMF 10 −11 V around the zero-resistance loop leading to a loop’s magnetic flux oscillating in time. It is shown its theoretical value is proportional to both the temperature difference as well as the disparity in the thermoelectric powers of the two junctions. PACS Number(s).: 74.50+r, 42.50.Dv Thermoelectric effects in superconductor- normal metal- superconductor (SNS) junctions have been studied theoretically and observed experimentally in the papers1−5. The purpose of this short Letter is to suggest from theoretical considerations a new proposal to measure thermoelectric effects in the SNS structures. We shall first consider the behaviour of a single Josephson junction when temperatures of its electrodes S have difference ∆T or, in other words, when there is a heat flow through the junction. We use resistively shunted model of the Josephson junction in which the latter is considered as a circuit made up of the superconducting junction itself and a normal resistance connected in parallel. Then, due to the Kirchoff’s first law, js = jn. According to Ohm’s law a normal component of a current in the junction is jn = λ E −λgradµe+λβgradT, where λ is electrical conductivity, µe is the chemical potential per unit charge and β is thermoelectric power. Density of the superconducting current flowing through the junction is related to the phase difference φ = ∆ϑ of superconducting wavefunction ψ = n 1/2 s e iϑ across the junction by 6 js = jc sin φ, where jc is the critical value of electric current density, ns and ms are the density and mass of Cooper pairs. Using the considered formulae and Josephson equation 6 − � ∂φ 2

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