Anomalous thermoelectric effects of ZrTe5 in and beyond the quantum limit

Recently, several measurement techniques had been successfully constructed in our Water-Cooled magnets with the highest field up to 38.5T and lowest temperature down to 0.3K. In this presentation, I will first explain the basic principles of these techniques and demonstrate their applications on topological materials. In the second part, I will introduce our recent study on the thermoelectric effects of ZrTe5 in a magnetic field. We found that the presence of the non-trivial electrons leads to the anomalous Nernst effect and quasi-linear field dependence of thermopower below the quantum limit. In the strong-field quantum limit, both the thermopower and Nernst signal exhibit exotic peaks. At higher magnetic fields, the Nernst signal has a sign reversal at a critical field where the thermopower approaches to zero. We propose that these anomalous behaviors can be attributed to the gap closing of the zeroth Landau bands in topological materials with the band inversion. Our understanding to the anomalous thermoelectric properties in ZrTe5 opens a new avenue for exploring Dirac physics in topological materials.