Dichotomy between the hole and electrons behavior in the multiband FeSe probed by ultra high magnetic fields

TL;DR

This study uses ultra-high magnetic fields to investigate the multiband electronic structure of FeSe, revealing distinct hole and electron behaviors and identifying multiple Fermi surface pockets through quantum oscillations and magnetotransport measurements.

Contribution

It introduces a novel method to determine the sign of cyclotron orbits in a compensated metal using magnetotransport data, advancing understanding of FeSe's multiband structure.

Findings

Confirmed multiband Fermi surface with small pockets

Identified the largest pocket as a hole band

Discovered an additional tiny high-mobility electron pocket

Abstract

Magnetoresistivity \r{ho}xx and Hall resistivity \r{ho}xy in ultra high magnetic fields up to 88T are measured down to 0.15K to clarify the multiband electronic structure in high-quality single crystals of superconducting FeSe. At low temperatures and high fields we observe quantum oscillations in both resistivity and Hall effect, confirming the multiband Fermi surface with small volumes. We propose a novel and independent approach to identify the sign of corresponding cyclotron orbit in a compensated metal from magnetotransport measurements. The observed significant differences in the relative amplitudes of the quantum oscillations between the \r{ho}xx and \r{ho}xy components, together with the positive sign of the high-field \r{ho}xy , reveal that the largest pocket should correspond to the hole band. The low-field magnetotransport data in the normal state suggest that, in addition to one hole and one almost compensated electron bands, the orthorhombic phase of FeSe exhibits an additional tiny electron pocket with a high mobility.