key: cord-0651168-2wjvgsff
authors: Li, Haoxiang; Fabbris, G.; Said, A. H.; Pai, Y. Y.; Yin, Q. W.; Gong, C. S.; Tu, Z. J.; Lei, H. C.; Sun, J. P.; Cheng, J.-G.; Wang, Ziqiang; Yan, Binghai; Thomale, R.; Lee, H. N.; Miao, H.
title: Conjoined Charge Density Waves in the Kagome Superconductor CsV3Sb5
date: 2022-02-28
journal: nan
DOI: nan
sha: ed7d91c995f5d1c7415bbb97d11719499e79c999
doc_id: 651168
cord_uid: 2wjvgsff

The intricate interplay between novel lattice geometry and spontaneous symmetry-breaking states is at the forefront of contemporary research on quantum materials. Recently, the observation of unconventional charge and pairing density waves in a kagome metal CsV3Sb5 brings out a new showcase for intertwined orders. While electronic instabilities in CsV3Sb5 are widely believed to originate from the V 3d-electrons residing on the 2-dimensional kagome sublattice, the pivotal role of Sb 5p-electrons for 3-dimensional orders is yet to be understood. Here, using resonant tender x-ray scattering and high-pressure X-ray scattering, we report a rare realization of conjoined charge density waves (CDW) in CsV3Sb5. At ambient pressure, we discover a resonant enhancement at Sb L1-edge (2s-5p) at the 2$times$2$times$2 CDW wavevectors. The resonance, however, is absent at the 2$times$2 CDW wavevectors. Applying hydrostatic pressure, we find the CDW transition temperatures to separate, where the 2$times$2$times$2 CDW emerges 4 K above the 2$times$2 CDW at 1GPa. Our results establish the coexistence of the 2$times$2 CDW and the 5p-electron assisted 2$times$2$times$2 CDW in CsV3Sb5. The evolution of the conjoined CDWs under pressure suggests the joint importance of electronic and phononic fluctuations for the double dome superconductivity.

transcend the phenomenology that could be derived from a sole V kagome sublattice near van Hove filling, and hence provides key information to understand the enlarged complexity of novel symmetry-breaking phases in CsV3Sb5.

We start by proving the different electronic origin of the 2´2 and 2´2´2 CDWs using resonant elastic x-ray scattering (REXS). As depicted in Fig. 2a , by tuning the photon energy to atomic absorption edges, orbital-resolved valence electrons that are involved in the CDW will be enhanced 3 . In the cuprate high-Tc superconductors, CDW intensity resonates at both O K-edge (1s ® 2p) 27 and Cu L3-edge (2p ® 3d) 28 Fig. 3a . Figure 3b shows the integrated CDW intensity at P=0. 5 (SoD) or inverse-SoD patterns 16, 30, 31 . First principles calculations showed that the inverse-SoD is energetically favored at zero temperature but nearly degenerate with the SoD pattern at high temperature 32, 33 . In the presence of Sb sublattices, both the kinetic energy (pz-pz bonding) and

Coulomb repulsion between 5p-electrons are sensitive to the lattice distortions. Figure 

Single crystals of CsV3Sb5 were grown from Cs ingot (purity 99.9 %), V powder (purity 99.9 %) and Sb grains (purity 99.999 %) using the self-flux method 34 . The mixture was put into an alumina crucible and sealed in a quartz ampoule under partial argon atmosphere. The sealed quartz ampoule was heated to 1273 K for 12 h and soaked there for 24 h. Then it was cooled down to 1173 K at 50 K/h and further to 923 K at a slowly rate. Finally, the ampoule was taken out from the furnace and decanted with a centrifuge to separate CsV3Sb5 single crystals from the flux. The obtained crystals have a typical size of 2´2´0.1 mm 3 . CDW transition is clearly observed in specific heat measurement as shown in the inset of Fig. 1d .

Resonant single crystal X-ray diffraction was performed at the 4-ID-D beamline of the Advanced Photon Source (APS), Argonne National Laboratory (ANL). The X-rays higher harmonics were suppressed using a Si mirror and by detuning the Si (111) monochromator. Diffraction was measured using a vertical scattering plane geometry and horizontally polarized (s) X-rays. The incident intensity was monitored by a He filled ion chamber, while diffraction was collected using a Si-drift energy dispersive detector with approximately 200 eV energy resolution. The probed absorption edges are close in energy (4.1-5.5 keV); thus, the use of this detector is key to reject the fluorescence background. The sample temperature was controlled using a He closed cycle cryostat and oriented such that X-rays scattered from the (001) surface.

High-pressure single crystal x-ray diffraction was also measured at the 4-ID-D beamline of the APS, ANL.

High pressure was generated using a modified Merrill-Bassett-type diamond anvil cell 35 fitted with a pair of Boehler-Almax anvils of 800 µm culet diameter. A stainless-steel gasket was indented to 70 µm and a sample chamber of 400 µm diameter was laser cut. 4:1 methanol:ethanol was used as pressure media.

Diffraction was measured in the transmission geometry in which X-rays penetrate through both diamond anvils and sample. The sample was cut into approximately 80´80´40 µm 3 and oriented such that the c-axis is parallel to the X-ray direction when q = 0 degree. Temperature was controlled using a He closed cycle cryostat. Pressure was calibrated as a function of temperature using the Au lattice constant 36 and controlled in-situ using a He gas membrane. X-ray energy of 20 keV was used to minimize the diamond anvil attenuation. The incident intensity was measured using a N2 filled ion chamber, and diffraction was collected using a NaI scintillator.

High-precision X-ray scattering measurements shown in Fig. 1c ,d was taken at 30-ID-C (HERIX), where the highly monochromatic X-ray beam of incident energy Ei = 23.7 keV (l= 0.5226 Å) was focused on the sample with a beam cross section of 35´15 µm 2 (horizontal´vertical). The total energy resolution of the monochromatic X-ray beam and analyzer crystals was DE~1.5 meV (full width at half maximum). The measurements were performed in transmission geometry. 

Colloquium: Theory of Intertwined Orders in High Temperature Superconductors

Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

Resonant X-Ray Scattering Studies of Charge Order in Cuprates

Charge order and broken rotational symmetry in magic-angle twisted bilayer graphene

Subllatice interference in the kagome Hubbard model

Comoeting electronic orders on kagome lattices at van Hove filing

Unconventional Fermi Surface Instabilities in the Kagome Hubbard Model

Chiral flux phase in the kagome superconductor AV3Sb5

Analysis of Charge Order in the Kagome Metal AV3Sb5 (A=K, Rb, Cs)

Complex charge density waves at van Hove singularity on hexagonal lattices: Haldane-model phase diagram and potential realization in kagome metals AV3Sb5

Electronic instabilities of kagome metals: Saddle points and Landau theory

Theory of the charge density wave in AV3Sb5 kagome metals

New kagome prototype materials: Discovery of KV3Sb5, RbV3Sb5, CsV3Sb5

CsV3Sb5: A Z2 Topological Kagome Metal with a Superconducting Ground State

Giant, unconventional anomalous Hall effect in the metallic frustrated mag-net candidate

Unconventional chiral charge order in kagome superconductor KV3Sb5

Three-Dimensional Charge Density Wave and Surface-Dependent Vortex-Core States in a Kagome Superconductor CsV3Sb5

Observation of Unconventional Charge Density Wave without Acoustic Phonon Anomaly in Kagome Superconductors AV3Sb5

Double Superconducting Dome and Triple Enhancement of Tc in the Kagome Superconductor CsV3Sb5 under High Pressure

Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal

Pressure-induced reemergence of superconductivity in the topological kagome metal CsV3Sb5

Cascade of correlated electron states in the kagome superconductor CsV3Sb5

Roton pair density wave in a strong-coupling kagome. superconductor

Time-reversal symmetry-breaking charge order in a kagome superconductor

Charge-Density-Wave-driven electronic nematicity in a kagome superconductor

Role of Sb in the superconducting kagome metal CsV3Sb5 revealed by its anisotropic compression

Spatially Modulated "Mottness" in La2-xBaxCuO4

Long-Range Incommensurate Charge Fluctuations in (Y, Nd)Ba2Cu3O6+x

High-Temperature Charge Density Wave Correlations in La1.875Ba0.125CuO4 without Spin-Charge Locking

Geometry of the charge density wave in the kagome metal AV3Sb5

Fermi Surface Mapping and the Nature of Charge-Density-Wave Order in the Kagome Superconductor CsV3Sb5

Charge Density Waves and Electronic Properties of Superconducting Kagome Metals

Coherent phonon spectroscopy and interlayer modulation of charge density wave order in the kagome metal CsV3Sb5

Superconductivity and normal-state properties of kagome metal RbV3Sb5 single crystals

Miniature diamond anvil pressure cell for single crystal X-ray diffraction studies

Equations of State for Cu, Ag, and Au for Wide Ranges in Temperature and Pressure up to 500 GPa and Above

S-Wave Superconductivity in Kagome Metal CsV3Sb5 Revealed by 121/123 Sb NQR and 51 V NMR Measurements