Quantum critical phenomena and vortex states in two-dimensional superconductors probed by thermoelectric effects

We show that the thermoelectric Nernst measurement is suitable to detect fluctuations of the superconducting order parameter even in a low-temperature regime where quantum fluctuations play an important role. We apply this technique to study the field-induced superconductor-metal-insulator transition in two-dimensional superconductors, which is briefly reviewed in this article. We found an exotic quantum liquid state of superconducting vortices inside the anomalous metallic state and its quantum criticality by evaluating entropy. (author)