Strong correlation and low carrier density in Fe1+yTe0.6Se0.4 as seen from its thermoelectric response

Alexandre Pourret, Liam Malone, Arlei B. Antunes, C. S. Yadav, P. L. Paulose, Benoît Fauqué, and Kamran Behnia

We present a study of the Seebeck and Nernst coefficients of Fe1+yTe1-xSex extended up to 28 T. The large magnitude of the Seebeck coefficient in the optimally doped sample tracks a remarkably low normalized Fermi temperature, which like other correlated superconductors, is only one order of magnitude larger than Tc. We combine our data with other experimentally measured coefficients of the system to extract a set of self-consistent parameters, which identify Fe1+yTe0.6Se0.4 as a low-density correlated superconductor barely in the clean limit. The system is subject to strong superconducting fluctuations with a sizable vortex Nernst signal in a wide temperature window.

Phys. Rev. B 83, 020504(R) (2011)