Theory of a Large Thermoelectric Effect in Superconductors Doped with Magnetic Impurities

We argue that parametrically strong enhancement of a thermoelectric current can be observed in conventional superconductors doped by magnetic impurities. This effect is caused by the violation of the symmetry between electronlike and holelike excitations due to formation of subgap bound Andreev states in the vicinity of magnetic impurities. We develop a quantitative theory of this effect and demonstrate that it can be detected in modern experiments.

Figure 1

A ring formed by two different superconductors with contacts maintained at different temperatures $T_a$ and $T_b$.

Figure 2

Energy-resolved density of states $\nu (\epsilon )=\nu (-\epsilon )$ in a superconductor doped by magnetic impurities. $T_{c0}$ is the critical temperature of an undoped superconductor.

Figure 3

Thermoelectric coefficient as a function of temperature and magnetic impurity concentration. Scattering parameters $u_1=u_2=0.5$ and the scattering rate $\Gamma =10T_{c0}$ are the same for both panels.

Figure 4

Temperature dependence of the term $-4e\alpha {\lambda }^2{T}_{c0}/c^2$. Different curves correspond to different values $n_{\mathrm{imp}}$. The parameters $u_{1,2}$ and $\Gamma$ are the same as in Fig. 3.