Electron carriers with possible Dirac-cone-like dispersion in FeSe$_{1-x}$S$_x$ ($x$ = 0 and 0.14) single crystals triggered by structural transition

TL;DR

This study investigates the transport properties of FeSe$_{1-x}$S$_x$ single crystals, revealing a possible Dirac-cone-like state triggered by structural transition and showing how S doping affects orbital ordering and band structure.

Contribution

It provides new insights into how sulfur doping influences the structural transition, Dirac-like states, and orbital ordering in FeSe, supported by detailed transport measurements.

Findings

Linear magnetoresistance triggered by structural transition

Possible Dirac-cone-like state from band shift due to orbital order

Suppression of orbital ordering and changes in band structure with S doping

Abstract

We report detailed study of the transport properties of FeSe$_{1-x}$S$_x$ ($x$ = 0 and 0.14) single crystals grown by vapor transport method. 14\% S doping is found significantly suppress the structural transition from $T_s$ $\sim$ 86 K in FeSe to $\sim$ 49 K, although the superconducting transition temperature, $T_c$, is only slightly affected. A pronounced linear magnetoresistance (MR) is observed in both FeSe and FeSe$_{0.86}$S$_{0.14}$ single crystals, which is found to be triggered by the structural transition. The linear MR and related discussion indicate the possible existence of Dirac-cone-like state, which may come from the band shift induced by ferro-orbital order. The mobility of the Dirac-cone-like band is found to decrease after S doping. Besides, the invalid Kohler's scaling of MR is found for temperature below $T_s$ in both crystals, however the re-establishment of the Kohler's scaling at temperatures below 30 K is observed in FeSe, but not in FeSe$_{0.86}$S$_{0.14}$. All these observations above support that the orbital ordering causes the band reconstruction in FeSe, and also that the orbital ordering in FeSe is suppressed by the chemical pressure from S doping.