Charge density waves in strongly correlated electron systems

Chen, Chih‐Wei; Choe, Jesse; Morosan, Emilia

doi:10.1088/0034-4885/79/8/084505

Cited by 134 publications

(99 citation statements)

References 114 publications

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“…A typical CDW phase transition is accompanied by the opening of a gap at the Fermi level, resulting in a metal-to-insulator like transition in resistivity as a function of temperature. In most microscopic models, a CDW transition is understood as being driven by either an electron energy instability near the Fermi level, or due to Fermi nesting [35][36][37]. Most commonly, CDW phase transitions are observed in 1D chains [38], or in 2D layered di-chalogenide materials [39].…”

Section: Further Discussionmentioning

confidence: 99%

Possible lattice and charge order in Cu_xBi₂Te₂Se

Smith

Rexhausen

et al. 2019

J. Phys. Mater.

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Metal intercalation into layered topological insulator materials such as the binary chalcogenide Bi 2 X 3 (X=Te or Se) has yielded novel two-dimensional (2D) electron-gas physics, phase transitions to superconductivity, as well as interesting magnetic ground states. Of recent interest is the intercalationdriven interplay between lattice distortions, density wave ordering, and the emergence of new phenomena in the vicinity of instabilities induced by intercalation. Here, we examine the effects of Cu-intercalation on the ternary chalcogenide Bi 2 Te 2 Se. We report the discovery, in Cu 0.3 Bi 2 Te 2 Se, of a periodic lattice distortion (PLD) at room temperature, together with a charge density wave (CDW) transition around T d =220 K. We also report, for the first time, a complete study of the Cu x Bi 2 Te 2 Se system, and the effect of Cu-intercalation on crystal structure, phonon structure, and electronic properties for 0.0x0.5. Our electron diffraction studies reveal strong Bragg spots at reciprocal lattice positions forbidden by ABC stacking, possibly resulting from stacking faults, or a superlattice. The c-axis lattice parameter varies monotonically with x for 0<x<0.2, but drops precipitously for higher x. Similarly, Raman phonon modes A g 1 2 and E g 2 soften monotonically for 0<x<0.2 but harden sharply for x>0.2. This indicates that Cu likely intercalates up to x∼0.2, followed by partial site-substitutions at higher values. The resulting strain makes the 0.2x0.3 region susceptible to instabilities and distortions. Our results point toward the presence of an incommensurate CDW above T d =220 K. This work strengthens prevalent thought that intercalation contributes significantly to instabilities in the lattice and charge degrees of freedom in layered chalcogenides. Further work is required to uncover additional density wave transitions, and possible ground states such as superconductivity.

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Section: Further Discussionmentioning

confidence: 99%

Possible lattice and charge order in Cu_xBi₂Te₂Se

Smith

Rexhausen

et al. 2019

J. Phys. Mater.

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“…A good review about the CDWs in strongly correlated electron systems, especially in cuprate superconductors, is available in Ref. [73].…”

Section: Cdw In Cupratesmentioning

confidence: 99%

Misconceptions associated with the origin of charge density waves

Zhu

Guo

Zhang

et al. 2017

Advances in Physics: X

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Charge density wave (CDW) is an important concept in condensed matter physics, germane to a number of physical phenomena. But the origin of CDW is still under debate, partly because the origin and properties of CDW are highly materialdependent. The concept of a CDW has been applied to many materials without a clear definition of the fundamental nature of CDW. As a result, misconceptions about CDW can be seen in the literature. In this review, we will try to describe and explain the possible existing misconceptions associated with the origin of CDWs.

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“…Charge density waves (CDWs) are an important component in phase diagrams of many correlated electron systems [1,2]. Typically observed in low-dimensional materials, the signatures of a CDW phase have been reported in two-dimensional transition metal dichalcogenides (TMDs) [3], cuprate superconductors [4], -conjugated polymers [5] and metal oxides [6].…”

Section: Introductionmentioning

confidence: 99%

“…Typically observed in low-dimensional materials, the signatures of a CDW phase have been reported in two-dimensional transition metal dichalcogenides (TMDs) [3], cuprate superconductors [4], -conjugated polymers [5] and metal oxides [6]. The central importance of CDW states arises from the relationship between fluctuations in their order parameter and superconductivity, Mott insulating states, and spin density waves [1,7]. In the TMD 1T-TiSe2 superconductivity appears in proximity to CDW incommensurability [8], which can be achieved by pressure [9], copper doping [10], or electrostatic gating [11].…”

Section: Introductionmentioning

confidence: 99%

Excitonic and lattice contributions to the charge density wave in 1T−TiSe2 revealed by a phonon bottleneck

Hedayat

Sayers

Bugini

et al. 2019

Phys. Rev. Research

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Understanding collective electronic states such as superconductivity and charge density waves is pivotal for fundamental science and applications. The layered transition metal dichalcogenide 1T-TiSe2 hosts a unique charge density wave (CDW) phase transition whose origins are still not fully understood. Here, we present ultrafast time-and angleresolved photoemission spectroscopy (TR-ARPES) measurements complemented by time-resolved reflectivity (TRR) which allows us to establish the contribution of excitonic and electron-phonon interactions to the CDW. We monitor the energy shift of the valence band (VB) and coupling to coherent phonons as a function of laser fluence. The VB shift, directly related to the CDW gap closure, exhibits a markedly slower recovery dynamics at fluences above Fth = 60 J cm -2 . This observation coincides with a shift in the relative weight of coherently coupled phonons to higher frequency modes in time-resolved reflectivity (TRR), suggesting a phonon bottleneck. Using a rate equation model, the emergence of a high-fluence bottleneck is attributed to an abrupt reduction in coupled phonon damping and an increase in exciton dissociation rate linked to the loss of CDW superlattice phonons. Thus, our work establishes the important role of both excitonic and phononic interactions in the CDW phase transition and the advantage of combining complementary femtosecond techniques to understand the complex interactions in quantum materials. Corresponding authorCorrespondence to Enrico Da Como edc25@bath.ac.uk APPENDIX A: TIME-DEPENDENCE OF FREE CARRIER POPULATION AND LINEARITY WITH PUMP FLUENCEIn order to check the linearity of the laser pumping effect in our TR-ARPES experiment, we have analysed the total intensity above the Fermi level, EF, for all spectra, which provides an indication of the transient free carrier population induced by the pump pulse. For this, we used the normalised spectra in Fig. 6 at each pump-probe delay and integrated across the high energy tail to intensity ≤ 0.25 (just below the nodal point of all spectra in the normal phase) as shown

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Charge density waves in strongly correlated electron systems

Cited by 134 publications

References 114 publications

Possible lattice and charge order in Cu_xBi₂Te₂Se

Possible lattice and charge order in Cu_xBi₂Te₂Se

Misconceptions associated with the origin of charge density waves

Excitonic and lattice contributions to the charge density wave in 1T−TiSe2 revealed by a phonon bottleneck

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Charge density waves in strongly correlated electron systems

Cited by 134 publications

References 114 publications

Possible lattice and charge order in CuxBi2Te2Se

Possible lattice and charge order in CuxBi2Te2Se

Misconceptions associated with the origin of charge density waves

Excitonic and lattice contributions to the charge density wave in 1T−TiSe2 revealed by a phonon bottleneck

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Possible lattice and charge order in Cu_xBi₂Te₂Se

Possible lattice and charge order in Cu_xBi₂Te₂Se