Doping evolution of superconductivity, charge order and band topology in hole-doped topological kagome superconductors Cs(V$_{1-x}$Ti$_x$)$_3$Sb$_5$

Liu, Yixuan; Wang, Yuan; Cai, Yongqing; Hao, Zhanyang; Ma, Xiaoming; Wang, Le; Liu, Cai; Chen, Jian; Zhou, Liang; Wang, Jinhua; Wang, Shanming; He, Hongtao; Liu, Yi; Cui, Shengtao; Wang, Jianfeng; Huang, Bing; Chen, Chao‐Yu; Mei, Jia‐Wei

doi:10.48550/arxiv.2110.12651

Cited by 10 publications

(15 citation statements)

References 43 publications

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“…Previous high-pressure measurements on this kagome metal system AV 3 Sb 5 show that superconductivity coexists with CDW order under ambient pressure, however superconducting T c increases while T CDW decreases with increasing pressure, suggesting a competition between CDW order and superconductivity [9,25,34,35]. Evidence for such competition is also provided by holedoping studies [34,36,37], systematic studies of finite crystal thickness [34,38], and measurements under uniaxial strain [39]. In contrast, our x-ray results on the ambient pressure CDW state in CsV 3 Sb 5 show it to be robust and to co-exist well with its superconducting instability below T c = 2.9 K, at least as low as T = 2 K.…”

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confidence: 57%

Charge density wave order and fluctuations above T$_{CDW}$ and below superconducting T$_c$ in the kagome metal CsV$_{3}$Sb$_{5}$

Chen,

Schnelle

et al. 2022

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The phase diagram of the kagome metal family AV 3 Sb 5 (A = K, Rb, Cs) features both superconductivity and charge density wave (CDW) instabilities, which have generated tremendous recent attention. Nonetheless, significant questions remain. In particular, the temperature evolution and demise of the CDW state has not been extensively studied, and little is known about the co-existence of the CDW with superconductivity at low temperatures. We report an x-ray scattering study of CsV 3 Sb 5 over a broad range of temperatures from 300 K to ∼ 2 K, below the onset of its superconductivity at Tc ∼ 2.9 K. Order parameter measurements of the 2 × 2 × 2 CDW structure show an unusual and extended linear temperature dependence onsetting at T * ∼ 160 K, much higher than the susceptibility anomaly associated with CDW order at TCDW = 94 K. This implies strong CDW fluctuations exist to ∼ 1.7 × TCDW. The CDW order parameter is observed to be constant from T = 16 K to 2 K, implying that the CDW and superconducting order co-exist below Tc, and, at ambient pressure, any possible competition between the two order parameters is manifested at temperatures well below Tc, if at all. Anomalies in the temperature dependence in the lattice parameters coincide with TCDW for c(T ) and with T * for a(T ).

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confidence: 57%

Charge density wave order and fluctuations above T$_{CDW}$ and below superconducting T$_c$ in the kagome metal CsV$_{3}$Sb$_{5}$

Chen,

Schnelle

et al. 2022

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“…These results establish a solid foundation to study the interplay between the primary and secondary CDW order parameters in kagome metal system. They guide to identify the primary and secondary order parameters as well as their interplay, when these CDW order parameters are tuned by carrier doping [26][27][28], external pressure [24,25], or strain [66]. We choose êi and ês to be X, Y , R, and L, where X = (1 0 0), Y = (0 1 0), R = 1/ √ 2 (1 i 0), and L = 1/ √ 2 (1 − i 0).…”

Section: Discussionmentioning

confidence: 99%

“…in AV 3 Sb 5 , as T c increases when the CDW order is suppressed by hydrostatic pressure [24,25], or by the hole doping [26][27][28], or by thickness reduction [28,29]. Furthermore, the CDW state shows a large extrinsic anomalous Hall effect [30,31] in the absence of magnetic ordering [32].…”

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confidence: 99%

Charge density wave order in kagome metal AV$_3$Sb$_5$ (A= Cs, Rb, K)

Wu,

Ortiz,

Tan

et al. 2022

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We employ polarization-resolved electronic Raman spectroscopy and density functional theory to study the primary and secondary order parameters, as well as their interplay, in the charge density wave (CDW) state of the kagome metal AV3Sb5. Previous x-ray diffraction data at 15 K established that the CDW order in CsV3Sb5 comprises of a 2 × 2 × 4 structure: one layer of inverse-starof-David and three consecutive layers of star-of-David pattern. We analyze the lattice distortions based the 2 × 2 × 4 structure at 15 K, and find that U1 lattice distortion is the primary-like (leading) order parameter while M + 1 and L − 2 distortions are secondary-like order parameters for Vanadium displacements. This conclusion is confirmed by the calculation of bare susceptibility χ 0 (q) that shows a broad peak at around qz = 0.25 along the hexagonal Brillouin zone face central line (Uline). We also identify several phonon modes emerging in the CDW state, which are lattice vibration modes related to V and Sb atoms as well as alkali atoms. The detailed temperature evolution of these modes' frequencies, half-width-at-half-maximums, and integrated intensities support a phase diagram with two successive structural phase transitions in CsV3Sb5: the first one with a primarylike order parameter appearing at TS = 94 K and the second isostructural one appearing at around T * = 70 K. Furthermore, the T -dependence of the integrated intensity for these modes show two types of behavior below TS: the low-energy modes show a plateau-like behavior below T * while the high-energy modes monotonically increase below TS. These two behaviors are captured by Landau free energy model incorporating the interplay between the primary-like and the secondarylike order parameters via trilinear coupling. Especially, the sign of the trilinear term that couples order parameters with different wave-vectors determines whether the primary-like and secondarylike order parameters cooperate or compete with each other, thus determining the shape of the T -dependence of the intensities of Bragg peak in x-ray data and the amplitude modes in Raman data below TS. These results provide an accurate basis for studying the interplay between multiple CDW order parameters in kagome metal systems. I. INTRODUCTIONKagome lattice is a model system to study the electronic and magnetic properties [1,2]. The corner shared triangle network of the kagome lattice enables three sublattice interference, which give rise to a variety of exotic physics, for example, flat bands, van Hove singularities, Dirac-dispersions in its electronic structure, frustrated magnetism, to name a few. Various electronic orders such as charge/spin density wave order, charge bond order, chiral flux order, nematic order, and superconductivity are under rigorous investigations [3][4][5][6][7][8][9][10][11][12][13][14][15][16].Recently, a three-dimensional charge density wave (CDW) order, which coexists with superconductivity (SC) at low temperatures, was discovered in AV 3 Sb 5 (A= Cs, Rb, K) kagome metals [Fig. 1 ...

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“…First principles calculations could relate our phase diagram to these experiments by determining δ, µ and couplings as a function of pressure. Variation of doping and pressure indicates the presence of two distinct superconducting phases [46][47][48]; it is possible that the TvHS dominates the physics in one doping regime, while other interaction physics could be important elsewhere in the phase diagram [82][83][84][85][86][87]-e.g. it has been shown that sublattice interference near the K-points can result in higher-order topological multigap s-or p-wave states [11,86,87].…”

Section: Discussionmentioning

confidence: 99%

Chiral excitonic order from twofold van Hove singularities in kagome metals

Scammell¹,

Ingham²,

Li³

et al. 2022

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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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Doping evolution of superconductivity, charge order and band topology in hole-doped topological kagome superconductors Cs(V$_{1-x}$Ti$_x$)$_3$Sb$_5$

Cited by 10 publications

References 43 publications

Charge density wave order and fluctuations above T$_{CDW}$ and below superconducting T$_c$ in the kagome metal CsV$_{3}$Sb$_{5}$

Charge density wave order and fluctuations above T$_{CDW}$ and below superconducting T$_c$ in the kagome metal CsV$_{3}$Sb$_{5}$

Charge density wave order in kagome metal AV$_3$Sb$_5$ (A= Cs, Rb, K)

Chiral excitonic order from twofold van Hove singularities in kagome metals

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