Testing electron–phonon coupling for the superconductivity in kagome metal CsV3Sb5

Abstract

In crystalline materials, electron-phonon coupling (EPC) is a ubiquitous many-body interaction that drives conventional Bardeen-Cooper-Schrieffer superconductivity. Recently, in a new kagome metal CsV3Sb5, superconductivity that possibly intertwines with time-reversal and spatial symmetry-breaking orders is observed. Density functional theory calculations predicted weak EPC strength, λ, supporting an unconventional pairing mechanism in CsV3Sb5. However, experimental determination of λ is still missing, hindering a microscopic understanding of the intertwined ground state of CsV3Sb5. Here, using 7-eV laser-based angle-resolved photoemission spectroscopy and Eliashberg function analysis, we determine an intermediate λ=0.45–0.6 at T = 6 K for both Sb 5p and V 3d electronic bands, which can support a conventional superconducting transition temperature on the same magnitude of experimental value in CsV3Sb5. Remarkably, the EPC on the V 3d-band enhances to λ~0.75 as the superconducting transition temperature elevated to 4.4 K in Cs(V0.93Nb0.07)3Sb5. Our results provide an important clue to understand the pairing mechanism in the kagome superconductor CsV3Sb5.

Crossover between electron-electron and electron-phonon mediated pairing on the kagome lattice

“…Especially, for the mul-014517-4 tiorbital AV 3 Sb 5 , where two p-type VHSs and one m-type VHS appear near the Fermi level [25,26], our work has implications for its pairing symmetry. First, it is noted that the pairing eigenvalue λ s without correlations (U = V = 0) is of the order of the values reported in first-principle calculations [42,47,58,59], confirming that our choice of phonon parameters is realistic for AV 3 Sb 5 . As nematicity emerges in the CDW order with the lattice rotational symmetry broken, the corresponding twofold pairing states may be split.…”

“…Moreover, μSR measurements [40] reveal a transition from a nodal to nodeless gap with increasing pressure, and they suggest that the nodeless pairing breaks time-reversal symmetry when the CDW order is suppressed by pressure. Recent angle-resolved photoemission spectroscopy measurements identified clear kinks in both Sb p-orbital and V d-orbital bands from which an intermediate electron-phonon coupling (EPC) strength was determined [42]. Thus, both electronic interactions (EIs) and EPC are believed to play crucial roles in promoting the exotic orders of AV 3 Sb 5 [43][44][45][46][47][48][49][50][51][52].…”

Unveiling the charge density wave mechanism in vanadium-based Bi-layered kagome metals

“…5(e) to mitigate the matrix element effect. In the vicinity of the Fermi level, a dispersion anomaly is observed at a binding energy of 35 meV within the hole-like band, reminiscent of kink behavior observed in AV 3Sb5 13,14 . Figure 5(f) displays the enlarged spectra of this band for ScV 6Sn6 with the incident photon energy of 75 eV, 84 eV, and 11 eV.…”

“…In particular, its charge density wave (CDW) state was reported to be a unique chiral flux phase with the timereversal symmetry breaking, which was regarded to be closely linked with unconventional superconductivity and intrinsic nematic order [5][6][7][8][9] , and consequently kindled a wave of intense studies on the CDW in AV 3Sb5. Nevertheless, despite significant progress on the origin of CDW in in AV 3Sb5, the fundamental controversy between the phonon softening and electronic susceptibility instability still persists [10][11][12][13][14] .…”

DNA as a perfect quantum computer based on the quantum physics principles

“…The lattice vibrations will decrease with the temperature reduction because entropy, representing disorder, also declines 98 . The resistance of some materials suddenly drops to zero below a specific temperature, called the critical Temperature 95 , 99 . They become superconducting, meaning they can conduct currents without energy loss.…”