Structural contributions to the pressure-tuned charge-density-wave to superconductor transition inZrTe3: Raman scattering studies

Abstract

Superconductivity evolves as functions of pressure or doping from charge-ordered phases in a variety of strongly correlated systems, suggesting that there may be universal characteristics associated with the competition between superconductivity and charge order in these materials. We present an inelastic light (Raman) scattering study of the structural changes that precede the pressuretuned charge-density-wave (CDW) to superconductor transition in one such system, ZrTe3. In certain phonon bands, we observe dramatic linewidth reductions that accompany CDW formation, indicating that these phonons couple strongly to the electronic degrees of freedom associated with the CDW. The same phonon bands, which represent internal vibrations of ZrTe3 prismatic rods, are suppressed at pressures above ∼10 kbar, indicating a loss of long-range order within the rods, specifically amongst intrarod Zr-Te bonds. These results suggest that the pressure-induced suppression of CDW order observed in ZrTe3 is structurally driven, and provide insights into the origin of pressure-induced superconductivity in this material.

Charge density waves and phonon-electron coupling inZrTe3

“…3(a), the background intensity exhibits an anomalous decrease with decreasing temperature. This has also been pointed out in a recent report [47]. The highly accurate data in Fig.…”

“…2(m) is crucial for the identification of their eigenvectors. Contrary to the assumption in previous reports [46,47], the frequencies of the A g modes are not well-separated into a low-and a highfrequency group. Therefore the A g modes cannot be simply attributed to inter-and intraZrTe3-prism vibrations.…”

“…A g modes can be observed in aa, bb, and cc polarizations, whereas B g modes can be observed in ab and bc polarizations. reports [46,47] and reveals a total of six phonon peaks, but it fails to detect two remaining A g modes, presumably due to unfavorable Raman-scattering matrix elements. These two modes become clearly visible in the cc spectrum.…”

Distinction between pristine and disorder-perturbed charge density waves in ZrTe3

“…A pronounced resistivity anomaly can be observed at 63 ± 1 K ( Supplementary Fig. 1), a temperature that is usually referred to as the CDW ordering temperature, T CDW , in earlier literature [34][35][36][37][38][39] . The Fermi surface, contributed by four bands, comprises two sectors ( Fig.…”

“…At even higher T, the diffraction pattern becomes smeared and weak to the point of being buried under the fluorescence background. Nonetheless, a CDW-related electronic gap 34,36 and suppression of phonon-damping effects 34,38 have been observed up to higher temperatures % 140 K, indicative of persisting shortrange charge correlations and fluctuations above T CDW . Diffuse scattering signals centered around q CDW , presumably related to thermally activated soft phonons, have been observed in hard Xray scattering experiments even up to room temperature 37 .…”