Magneto-Seebeck effect and ambipolar Nernst effect in CsV$_3$Sb$_5$ superconductor

TL;DR

This study investigates the magneto-Seebeck and ambipolar Nernst effects in the Kagome superconductor CsV$_3$Sb$_5$, revealing complex transport phenomena linked to charge density wave order and multi-band topology.

Contribution

It uncovers the interplay of Seebeck and Nernst effects with CDW order and multi-band topology in CsV$_3$Sb$_5$, highlighting novel transport behaviors without magnetic order.

Findings

Magneto-Seebeck signal appears below T_CDW=94 K.

Nernst signal peaks at T*=35 K with Hall coefficient sign change.

Large anomalous Nernst effect observed inside the CDW phase.

Abstract

We present a study of Seebeck and Nernst effect in combination with magnetoresistance and Hall measurements of the Kagome superconductor CsV$_3$Sb$_5$. Sizable magneto-Seebeck signal appears once the charge density wave (CDW) order sets in below $T_{CDW}$=94 K. The Nernst signal peaks at a lower temperature $T^*$=35 K, crossing which the Hall coefficient switches sign, which we attribute to the ambipolar transport of compensated bands due to the multi-band nature of CsV$_3$Sb$_5$. Sublinear Nernst signal as a function of magnetic field, together with large anomalous Nernst effect (ANE) also emerge inside the CDW phase, despite the absence of long-range magnetic order. These findings suggest that, the transport properties are dominated by small pockets with multi-band profile, and that the unusual band topology also plays an import role in the CDW state of CsV$_3$Sb$_5$.