Hysteretic melting transition of a soliton lattice in a commensurate charge modulation

Abstract

We report on the observation of the hysteretic transition of a commensurate charge modulation in IrTe${}_2$ from transport and scanning tunneling microscopy (STM) studies. Below the transition ($T_{\mathrm{C}}\approx 275$ K on cooling) a $q=1/5$ charge modulation was observed, which is consistent with previous studies. Additional modulations [$q_n=(3n+2{)}^{-1}$] appear below a second transition at $T_{\mathrm{S}}\approx 180$ K on cooling. The coexistence of various modulations persist up to $T_{\mathrm{C}}$ on warming. The atomic structures of charge modulations and the temperature dependent STM studies suggest that 1/5 modulation is a periodic soliton lattice which partially melts below $T_{\mathrm{S}}$ on cooling. Our results provide compelling evidence that the ground state of IrTe${}_2$ is a commensurate 1/6 charge modulation, which originates from periodic dimerization of Te atoms visualized by atomically resolved STM images.

5 pages, 5 figures