Giant Nernst Effect in ${\mathrm{CeCoIn}}_5$

We present a study of Nernst and Seebeck coefficients of the heavy-fermion superconductor ${\mathrm{CeCoIn}}_5$. Below 18 K, concomitant with a field-dependent Seebeck coefficient, a large sublinear Nernst signal emerges with a magnitude drastically exceeding what is expected for a multiband Fermi-liquid metal. In the mixed state, in contrast with all other superconductors studied before, this signal overwhelms the one associated with the motion of superconducting vortices. The results point to a hitherto unknown source of transverse thermoelectricity in strongly interacting electrons.

Figure 1

(a) Temperature dependence of the Nernst coefficient for different magnetic fields. (b) Same for the Seebeck coefficient. Note also the zero-field data for the latter.

Figure 2

The ratio of transverse to longitudinal electric fields produced by the thermal current as a function of temperature (a) and magnetic field (b). This ratio represents the tangent of the angle between the longitudinal thermal current and the induced electric field, $\tan {\theta }_{\mathrm{TE}}$. The inset in (a) represents the sample geometry and miscellaneous vectors. For comparison, the temperature dependence of the electric Hall angle, ${\rho }_{xy}/{\rho }_{xx}$, is also plotted in (a).

Figure 3

Temperature dependence of the Nernst signal (a) and the Seebeck coefficient (b) for different magnetic fields in the vicinity of the superconducting transition. In panel (c), the difference between the Nernst signal and a fraction of the Seebeck signal at 0.5 T is plotted vs temperature and compared with the temperature dependence of the resistivity (solid line) measured in the same conditions.