Single crystal growth by self-flux method of the mixed valence gold halides Cs$_2$[Au$^{I}$X$_2$][Au$^{III}$X$_4$] (X=Br,I)

摘要

High quality single crystals of Cs$_2$Au$_2$X$_6$ (X=Br,I) were grown using aternary self-flux method. Structural refinements based on single crystal X-raydiffraction measurements show that both materials have a distorted perovskitestructure belonging to the I4/mmm space group with full site occupancy.Transport measurements reveal a large bandgap of 550 $\pm$ 100 meV forCs$_2$Au$_2$I$_6$ and 520 $\pm$ 80 meV for Cs$_2$Au$_2$Br$_6$. Initial attemptsat chemical substitution are described.