Observation of spin-orbit insulator-like behavior in LaOBiS${}_{2-x}$F${}_x$ (0.05 $\le$ $x$ $\le$ 0.2)

Abstract

We report the effects of electron doping on the crystal structure and electrical resistivity of LaOBiS${}_{2-x}$F${}_x$ (0.05 $\le$ $x$ $\le$ 0.2). The $ab$ plane is found to be relatively insensitive to the amount of F, whereas the $c$ axis shrinks continuously with increasing $x$, suggesting that the doped F atoms substitute selectively into the apical sites in the BiS${}_2$ layer. At $x$ = 0.10, as the temperature is decreased from room temperature, the electrical resistivity is temperature-independent from room temperature to 285 K, increases linearly with decreasing temperature from 285 K to 205 K and then shows obvious insulating behavior below 205 K, which may be due to strong spin-orbit coupling. LaOBiS${}_{1.9}$F${}_{0.1}$ shows the significantly weak and temperature-independent diamagnetism without any evident anomalies caused by a phase transition.