Gaussian Superconducting Fluctuations, Thermal Transport, and the Nernst Effect

We calculate the contribution of superconducting fluctuations to thermal transport in the normal state, at low magnetic fields. We do so in the Gaussian approximation to their critical dynamics which is also the Aslamazov-Larkin approximation in the microscopics. Our results for the thermal conductivity tensor and the transverse thermoelectric response are new. The latter compare favorably with the data of Ong and collaborators on the Nernst effect in the cuprates.

Figure 1

Points are ${\sigma }_{xx}(\nu -{\nu }^n)$ for different samples of ${\mathrm{L}\mathrm{a}}_{2-x}{\mathrm{S}\mathrm{r}}_x\mathrm{C}\mathrm{u}{\mathrm{O}}_{\mathrm{4}}$ [22], with $x=0.12$ (underdoped, $T_c=29\mathrm{K}$), $x=0.17$ (near optimal doping, $T_c=36\mathrm{K}$), and $x=0.2$ (overdoped, $T_c=27\mathrm{K}$). The solid line is the theoretical value of ${\alpha }_{xy}^{\mathrm{S}\mathrm{C}}/B$, using ${\xi }_{ab}^{\left(0\right)}=30Å$ and an anisotropy of $\gamma =20$. The dashed line is obtained using a Hartree approximation (see text).