Interplay between multiple charge-density waves and the relationship with superconductivity inPdxHoTe3

Abstract

HoTe3, a member of the rare-earth tritelluride (RTe3) family, and its Pd-intercalated compounds, PdxHoTe3, where superconductivity (SC) sets in as the charge-density wave (CDW) transition is suppressed by the intercalation of a small amount of Pd, are investigated using angle-resolved photoemission spectroscopy (ARPES) and electrical resistivity. Two incommensurate CDWs with perpendicular nesting vectors are observed in HoTe3 at low temperatures. With a slight Pd intercalation (x = 0.01), the large CDW gap decreases and the small one increases. The momentum dependence of the gaps along the inner Fermi surface (FS) evolves from orthorhombicity to near tetragonality, manifesting the competition between two CDW orders. At x = 0.02, both CDW gaps decreases with the emergence of SC. Further increasing the content of Pd for x = 0.04 will completely suppress the CDW instabilities and give rise to the maximal SC order. The evolution of the electronic structures and electron-phonon couplings (EPCs) of the multiple CDWs upon Pd intercalation are carefully scrutinized. We discuss the interplay between multiple CDW orders, and the competition between CDW and SC in detail. The recent observation of charge ordering in cuprate high-temperature superconductors 1,2 has reignited interests in CDW and its interplay with SC. A new charge ordering is always introduced by different types of instabilities, such as lattice distortion or FS nesting. However, the driving force behind the CDW phase is still under debate.3-15 From a Peierls perspective, in an ideal one-dimensional (1D) system, the electronic susceptibility would develop a logarithmic divergence singularity at some sheets of the FSs spanning by nesting vectors via EPCs, and hence results in a phase transition to the CDW ground state accompanied by the commensurate/incommensurate periodic lattice distortions and the opening of energy gaps at E F .3,4 Although, the quasi two-dimensional (2D) materials have a weaker tendency towards the nesting-driven CDWs owing to the imperfect nesting caused by the increased FS curvature, the electronic susceptibility could still be enhanced sufficiently for a CDW to develop under favorable nesting conditions and EPCs.16-19 Therefore, the CDW states in quasi 2D systems are particularly attractive due to the existence of possible multiple nesting properties and interacting collective orders added by the extra dimensionality.The fairly simple electronic structure of RTe 3 , where the CDW instabilities usually develop in the planar square nets of tellurium, 14 provides an unprecedented opportunity to systematically investigate the CDW formation and its relationship with FS nesting under pretty accurate theoretical models. An incommensurate CDW modulation characterized by a wave vector q 1 ≈ 2/7c * was commonly observed. [20][21][22][23] Recently, a second CDW transition occurs at lower temperatures with q 2 ≈ 1/3a * perpendicular to the first was discovered in heavier members of RTe 3 .19,23,24 Additionally, by the Pd intercalation, the suppres...

Suppression of charge density wave order by disorder in Pd-intercalated ErTe3

“…Significantly, the presence of Friedel oscillations in both a ⇤ ad c ⇤ directions would naturally lead to partial gapping of the Fermi surface in both directions, providing an alternative explanation for the approximately 4-fold symmetric gaps observed previously in Pd x HoTe 3 41 .…”

“…38,39 Polycrystalline samples of Pd x RTe 3 (R=Y, La, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm) have been reported previously 40 , and it was established that for high enough x, the material superconducts with T c ⇡2-3 K regardless of the chosen rare earth. Single crystal measurements have only previously been reported in Pd x HoTe 3 41 , and only the remnant of the first CDW transition was observed. From this it was assumed that the two CDWs merge together and appear simultaneously at a single crossover, which was supported by an observation that the two CDW gaps, while very di↵erent in the x = 0 parent compound, become indistinguishable for x 6 = 0.…”

“…From this it was assumed that the two CDWs merge together and appear simultaneously at a single crossover, which was supported by an observation that the two CDW gaps, while very di↵erent in the x = 0 parent compound, become indistinguishable for x 6 = 0. In the same work, the decrease in the orthorhombicity observed in the electronic structure was taken as evidence of either competition between the two CDW states, or a lattice distortion 41 . In this work, we show transport, magnetometry, x-ray, and electron di↵raction studies on samples of Pd x ErT 3 , and observe that the vestigial signatures of both of the phase transitions are suppressed independently (contrary to previous claims) and that significant CDW correlations appear in both directions, even once the resistivity signature of the second CDW has been suppressed to 0 K. In contrast to the previous papers, our study demonstrates that the decrease in electronic orthorhombicity is caused not by competition between the two CDW states, but rather as a consequence of the intrinsic electronic response of the Te planes to point defects, which overwhelms the small energy scale of the orthorhombicity.…”

Evidence for realignment of the charge density wave state in ErTe$_3$ and TmTe$_3$ under uniaxial stress via elastocaloric and elastoresistivity measurements

“…This work motivates the application of x-ray scattering and ARPES studies of RTe 3 under strain to further quantify the behavior and characteristics of the strain-induced q a state. More broadly, extension of the techniques presented here to samples with quenched disorder, such as Pd x RTe 3 [51,52] may also provide unique insight into frustrated charge order on a tetragonal lattice under uniaxial stress. More broadly, This work provides guiding principles for the study of the general behavior of unidirectional CDW phases and lays the foundation for future, more specialized explorations.…”

Suppression of charge density wave order by disorder in Pd-intercalated ErTe$_3$

“…35,36 Polycrystalline samples of Pd x RTe 3 (R=Y, La, Pr, Sm, Gd, Tb, Dy, Ho, Er, Tm) have been reported previously 37 , and it was established that for high enough x, the material superconducts with T c ≈2-3 K regardless of the chosen rare earth. Single crystal measurements have only previously been reported in Pd x HoTe 3 38 , and only the remnant of the first CDW transition was observed. From this it was assumed that the two CDWs merge together and appear simultaneously at a single crossover.…”