Electron carriers with possible Dirac-cone-like dispersion inFeSe1−xSx(x=0and 0…

We report detailed study of the transport properties of ${\mathrm{FeSe}}_{1\ensuremath{-}x}{\mathrm{S}}_{x}$ ($x$ = 0 and 0.14) single crystals grown by vapor transport method. 14% S doping is found to significantly suppress the structural transition from ${T}_{s}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}$ 86 K in FeSe to $\ensuremath{\sim}49$ K, although the superconducting transition temperature ${T}_{c}$ is only slightly affected. A pronounced linear magnetoresistance (MR) is observed in both FeSe and ${\mathrm{FeSe}}_{0.86}{\mathrm{S}}_{0.14}$ 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 reestablishment of the Kohler's scaling at temperatures below 30 K is observed in FeSe, but not in ${\mathrm{FeSe}}_{0.86}{\mathrm{S}}_{0.14}$. 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.