Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2104.08042

Multiple Energy Scales and Anisotropic Energy Gap in the Charge-Density-Wave Phase of Kagome Superconductor CsV3Sb5

Kosuke Nakayama·Yongkai Li·Takemi Kato·Min Liu·Zhiwei Wang·Takashi Takahashi·Yugui Yao·Takafumi Sato
View original source ↗Read source document ↗Export metadata ↓

Abstract

Kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit superconductivity at 0.9-2.5 K and charge-density wave (CDW) at 78-103 K. Key electronic states associated with the CDW and superconductivity remain elusive. Here, we investigate low-energy excitations of CsV3Sb5 by angle-resolved photoemission spectroscopy. We found an energy gap of 70-100 meV at the Dirac-crossing points of linearly dispersive bands, pointing to an importance of spin-orbit coupling. We also found a signature of strongly Fermi-surface and momentum-dependent CDW gap characterized by the larger energy gap of maximally 70 meV for a band forming a saddle point around the M point, the smaller (0-18 meV) gap for a band forming massive Dirac cones, and a zero gap at the Gamma-centered electron pocket. The observed highly anisotropic CDW gap which is enhanced around the M point signifies an importance of scattering channel connecting the saddle points, laying foundation for understanding the nature of CDW and superconductivity in AV3Sb5.

Explore related subjects

cond-mat.supr-concond-mat.mes-hall

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Kosuke Nakayama, Yongkai Li, Takemi Kato, Min Liu, Zhiwei Wang, Takashi Takahashi, Yugui Yao, Takafumi Sato. 2021-10-07. Multiple Energy Scales and Anisotropic Energy Gap in the Charge-Density-Wave Phase of Kagome Superconductor CsV3Sb5. https://doi.org/10.1103/physrevb.104.l161112

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Theoretical Prediction of Optimal $T_c$ and Fermi Pockets in Nickelate Superconductors

High-pressure bilayer $La_{3-x}Sm_{x}Ni_{2}O_{7-δ}$ (LSNO) reaches a record $T_c=96 K$, triggering wide discussion on the $T_c$ ceiling of nickelate superconductors. We show monoclinic and tetragonal LSNO share the same octahedral quantum-well motif governing $T_c$ with $YBa_{2}Cu_{3}O_{7-δ}$ (YBCO). Using the Planckian quantum-well scaling $T_c = Λ/ξ^{2}$ ($ξ$: lattice-modulated quantum-well depth), we obtain $T_c=93.4 K$ and $97.1 K$ for monoclinic and tetragonal LSNO, matching experimental values $92 K$ and $96 K$. Despite distinct stoichiometry and global symmetry ($P2_1/m$ for LSNO, $Pmmm$ for orthorhombic YBCO), both systems have nearly identical $ξ$ ($3.6629$ angstrom vs. $3.6720$ angstrom) and consistent $T_c$ responses. Further calculations yield a universal $T_c$ limit $\sim100 K$ for rare-earth nickelates, irrespective of stacking sequences. We examine four nickelate multilayer stacking variants: 2222 (pure bilayer), 1212 (alternating single-bilayer), 2323 (bilayer-trilayer), and 1313 (single-trilayer). Mirror symmetry breaking of coupled twin quantum wells, unique to bilayer nickelates, dictates $γ$ Fermi pocket formation and ambient-pressure superconductivity. We further prove Fermi surfaces constitute a hologram of quantum-well electrons, establishing intrinsic links between quantum-well symmetry breaking, Fermi pocket structural evolution, and superconducting properties.

cond-mat.supr-con↗
arXiv2026

Enhanced superconductivity in palladium hydrides by non-perturbative electron-phonon effects

Palladium hydrides exhibit the largest isotope-effect anomaly in superconductivity: replacing hydrogen with heavier isotopes increases the superconducting critical temperature. Although this behavior is commonly attributed to strong anharmonic hydrogen vibrations, \textit{ab initio} treatments have so far incorporated anharmonic effects only through phonon renormalization, neglecting non-linear contributions to the electron-phonon interaction vertices. While such approaches reproduce the anomalous isotope trend, they severely underestimate the critical temperatures. Here, we show that non-linear electron-phonon coupling is essential in palladium hydrides. A straightforward inclusion of higher-order perturbative terms leads to a qualitative breakdown: the critical temperature is overestimated and the isotope anomaly is lost. We therefore adopt a non-perturbative framework based on an explicit evaluation of the ion-mediated electron-electron interaction, enabling anharmonic effects to be treated consistently in both the phonon spectra and the interaction vertices. Applied to PdH and PdD, it restores the anomalous isotope effect and brings calculated critical temperatures into significantly improved agreement with experiments.

cond-mat.supr-con↗
arXiv2026

Optical manifestations of loop currents in Haldane's model and in time-reversal-breaking superconductors

We present a theoretical study of optical manifestations of loop currents in Haldane's model and in time-reversal-breaking superconductors. For Haldane's model, we calculate the expectation value of loop currents in terms of model parameters and relate it with the integrated optical spectral weight for the frequency-dependent ac Hall conductivity. Thus, experimental measurements of the latter can provide information about the presence and magnitude of steady loop currents in the system. Then we elaborate on loop currents in a chiral superconductor on the honeycomb lattice, studied earlier by Brydon et al. (2019). We demonstrate that a sharp optical absorption peak in the ac Hall conductivity originates from excitations between the lower and upper Dirac bands, activated by the time-reversal-breaking superconductivity. The frequency of the peak is twice the energy difference between the Fermi level and the Dirac point. The optical spectral weight of the peak is directly related to the magnitude of loop currents induced in the unit cells by the chiral superconducting pairing, in similarity to Haldane's model.

cond-mat.supr-con↗