Competing Soft Phonon Modes at the Charge-Density-Wave Transitiions in DyTe{sub 3}.
Authors
Maschek, M.; Zocco, D.; Rosenkranz, S.; Heid, R.; Said, A.; Alatas, A.; Walmsley, P.; Fisher, I.; Weber, F.
Abstract
The family of rare-earth tritellurides RTe3 features charge-density-wave (CDW) order related to strongly momentum-dependent electron-phonon coupling. Similar to other CDW compounds, superconductivity is observed when the CDW order is suppressed via hydrostatic pressure [1]. What sets the heavier members of the RTe3 series apart is the observation of a second CDW transition at lower temperatures having an in-plane ordering wavevector qCDW.2 || [100] of almost the same magnitude but orthogonal to the ordering wavevector qCDW.1 || [001] observed at higher temperatures [2]. Here, we report an inelastic x-ray scattering investigation of the lattice dynamics of DyTe3. In particular, we show that there are several phonon modes along both in-plane directions, which respond to the onset of the CDW transition at TCDW.1 = 308 K. Surprisingly, these soft modes close to qCDW.2 = (0.68, 0, 0) show strong softening near TCDW.1 but do not exhibit any response to the lower-temperature transition at TCDW.2 = 68 K. Our results indicate that the low-temperature CDW order is not just the 90° rotated analogue of the one appearing at high temperatures.