Charge ordered phases in IrTe2 revealed by coherent phonon spectroscopy

Abstract

Transition metal dichalcogenide IrTe2 undergoes structural transitions together with charge ordering due to formation of Ir dimers. Various low temperature phases of IrTe2 have been reported. However, the true ground state still remains controversial. We present three kinds of coherent oscillations in bulk IrTe2 at low temperatures probed by near infrared pump-probe spectroscopy. The temperature dependent evolution suggests that the charge ordered phase with (1/6 0 1/6) modulation vector develops in a bulk at the lowest temperature, which changes to a (1/8 0 1/8) modulation state around 235 K during warming up. The observed phonon spectra should provide a key to confirm the low temperature structures.