Twofold van Hove singularity and origin of charge order in topological kagome superconductor CsV3Sb5

Kang, Mingu; Fang, Shiang; Kim, Jeong‐Kyu; Ortiz, Brenden R.; Ryu, Sae Hee; Kim, Jimin; Yoo, Jonggyu; Sangiovanni, Giorgio; Sante, Domenico Di; Park, Byeong‐Gyu; Bostwick, Aaron; Rotenberg, Eli; Kaxiras, Efthimios; Wilson, Stephen D.; Park, Jaehoon; Comin, Riccardo

doi:10.48550/arxiv.2105.01689

Cited by 23 publications

(33 citation statements)

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“…We note that for the vanadium metals, the TvHS arises due to different d-orbitals within the kagome layer [52]; our toy model is not intended to capture the microscopic origin of the TvHS in these materials.…”

Section: A Tvhs Toy Modelmentioning

confidence: 99%

“…x − √ 3k x k y ) although it has been suggested that ARPES data on the vanadium metals are better fit by a quartic saddle-point for the hole-like Fermi surface denoted as 'ptype' [52]. Accounting for the quartic saddle-point would introduce a stronger divergence in the density of states at the p-type patches, but a weakening of the nesting effect as the p-type Fermi contour is distorted from the hexagonal shape.…”

Section: B Two-flavour Patch Modelmentioning

confidence: 99%

“…Systems with hexagonal Fermi surfaces, corresponding to saddle points in the electronic dispersion, have been predicted to give rise to chiral superconductivity and competing density wave order, due to the effects of Fermi surface nesting [57]. However, ARPES and DFT results reveal that the hexagonal Fermi surfaces in the vanadium metals exhibit an unusual feature-two-fold van Hove singularities (TvHS), for which the saddle points at each Fermi surface possess opposite concavity, resulting in one electron-like Fermi surface and one hole-like Fermi surface [52].…”

Section: Introductionmentioning

confidence: 99%

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Chiral excitonic order from twofold van Hove singularities in kagome metals

Scammell¹,

Ingham²,

Li³

et al. 2022

Preprint

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Recent experiments on kagome metals AV3Sb5 (A=K,Rb,Cs) [M. Kang et al., arXiv:2105.01689 (2021] identify twofold van Hove singularities (TvHS) with opposite concavity near the Fermi energy, generating two approximately hexagonal Fermi surfaces-one electron-like and the other hole-like.Here we propose that the TvHS are responsible for the novel charge and superconducting order observed in kagome metals. We introduce a model of a quasi-two dimensional system hosting a TvHS, and investigate the interaction induced many-body instabilities via the perturbative renormalisation group technique. The TvHS generates a topological d-wave excitonic condensate, arising due to bound pairs of electrons and holes located at opposite concavity vHS. Varying the chemical potential, detuning from the TvHS, and tuning the bare interaction strength, we construct a phase diagram which features the excitonic condensate alongside d-wave superconductivity and spin density wave order. The chiral excitonic state supports a Chern band giving rise to a quantum anomalous Hall conductance, providing an appealing interpretation of the observed anomalous Hall effect in kagome metals. Possible alternative realisations of the TvHS mechanism in bilayer materials are also discussed. We suggest that TvHS open up interesting possibilities for correlated phases, enriching the set of competing ground states to include excitonic order.

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Section: A Tvhs Toy Modelmentioning

confidence: 99%

Section: B Two-flavour Patch Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Chiral excitonic order from twofold van Hove singularities in kagome metals

Scammell¹,

Ingham²,

Li³

et al. 2022

Preprint

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“…The recently discovered kagome metals AV 3 Sb 5 (A = K, Rb, or Cs) [11,12] offer a new platform to study the interplay of these phenomena. These compounds have Fermi levels close to Dirac points or van Hove singularities [12][13][14], leading to a plethora of possible intriguing ground states. Indeed, charge-density waves and superconductivity have been discovered [12,15,16], with ample evidence showing that both types of orders are exotic.…”

Section: Introductionmentioning

confidence: 99%

Observation of anomalous amplitude modes in the kagome metal CsV$_3$Sb$_5$

Liu,

Ma,

et al. 2022

Preprint

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We report Raman scattering spectroscopy of the kagome metal CsV3Sb5 to investigate its chargedensity wave (CDW) phase. Temperature-dependent measurements reveal a multitude of CDWinduced modes, in agreement with density-functional theory calculations assuming the inverse Star of David lattice distortion. They are shown to be strongly hybridized amplitude modes and zonefolded modes, different from those in other known CDW materials. These CDW modes show negligible magnetic-field dependence and a signature of c-axis CDW modulation. Reducing the thickness to tens of nanometers dramatically enhances the change in the lattice phonon parameters across the CDW transition and strengthens its first-order character, indicating sizable electronphonon coupling. Further thickness reduction leads to destruction of the crystal lattice. Our results provide essential structural information to unravel the CDW mechanism in CsV3Sb5.

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“…While the exact nature of the high-temperature anomaly is still under debate, the robust nature of this transition under external magnetic fields suggests chargedensity wave (CDW) as the plausible origin. Indeed, band saddle points (van Hove singularities) observed in AV 3 Sb 5 in the vicinity of the Fermi level [11][12][13] should lead to a CDW instability of a kagome metal [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Optical study of RbV$_3$Sb$_5$: Multiple density-wave gaps and phonon anomalies

Wenzel,

Ortiz,

Wilson

et al. 2021

Preprint

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Temperature-dependent reflectivity studies on the non-magnetic kagome metal RbV3Sb5 in a broad energy range (50 cm −1 -20000 cm −1 ; 6 meV -2.5 eV) down to 10 K are reported. Below TCDW=102 K, the optical spectra demonstrate a prominent spectral-weight transfer from low to higher energies as the fingerprint of the charge-density wave (CDW) formation with the opening of a partial gap. A detailed analysis reveals two energy scales of, respectively, ∼ 100 meV and 45 meV, the latter appearing only below 50 K. Additionally, two modes at, respectively, 160 cm −1 and 430 cm −1 can be traced over the whole measured temperature range. Strong anomalies are observed for both of these modes already above TCDW with a further renormalization across TCDW, suggesting the importance of the electron-phonon coupling in RbV3Sb5 in both normal and CDW states. While the 160 cm −1 mode can be attributed to the E1u phonon, the 430 cm −1 mode could not be reproduced in our phonon calculations. The antiresonance nature of this mode gives hints for a nontrivial electron-phonon coupling in RbV3Sb5.

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Twofold van Hove singularity and origin of charge order in topological kagome superconductor CsV3Sb5

Cited by 23 publications

References 0 publications

Chiral excitonic order from twofold van Hove singularities in kagome metals

Chiral excitonic order from twofold van Hove singularities in kagome metals

Observation of anomalous amplitude modes in the kagome metal CsV$_3$Sb$_5$

Optical study of RbV$_3$Sb$_5$: Multiple density-wave gaps and phonon anomalies

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