Electronic nature of chiral charge order in the kagome superconductor CsV3Sb5

Abstract

Kagome superconductors with T C up to 7 K have been discovered for over 40 y. Recently, unconventional chiral charge order has been reported in kagome superconductor KV 3 Sb 5 , with an ordering temperature of one order of magnitude higher than the T C . However, the chirality of the charge order has not been reported in the cousin kagome superconductor CsV 3 Sb 5 , and the electronic nature of the chirality remains elusive. In this paper, we report the observation of electronic chiral charge order in CsV 3 Sb 5 via scanning tunneling microscopy (STM). We observe a 2 × 2 charge modulation and a 1 × 4 superlattice in both topographic data and tunneling spectroscopy. 2 × 2 charge modulation is highly anticipated as a charge order by fundamental kagome lattice models at van Hove filling, and is shown to exhibit intrinsic chirality. We find that the 1 × 4 superlattices form various small domain walls, and can be a surface effect as supported by our first-principles calculations. Crucially, we find that the amplitude of the energy gap opened by the charge order exhibits real-space modulations, and features 2 × 2 wave vectors with chirality, highlighting the electronic nature of the chiral charge order. STM study at 0.4 K reveals a superconducting energy gap with a gap size 2 = 0.85 meV, which estimates a moderate superconductivity coupling strength with 2 /k B T C = 3.9. When further applying a c-axis magnetic field, vortex core bound states are observed within this gap, indicative of clean-limit superconductivity.

Tunable nodal kagome superconductivity in charge ordered RbV3Sb5

“…Due to their inherent geometric frustration and unique band structure, kagome materials [1] represent an excellent platform for discovering, classifying and under-standing correlated electronic phases of quantum matter [2][3][4][5][6]. The novel family of kagome metals AV 3 Sb 5 (A = K, Rb, Cs) [7][8][9][10][11] exhibit an array of interesting effects such as giant anomalous Hall conductivity [12,13], charge order [11,[14][15][16][17][18][19][20][21][22], orbital order [23], and possible unconventional superconductivity [7,8,10]. An important feature of the charge order, which onsets at temperatures T co ∼ 100 K at ambient pressure, is the breaking of time-reversal symmetry, as reported by scanning tunneling microscopy (STM) measurements [11,14,15,17] in (K,Rb,Cs)V 3 Sb 5 , by muon spin relaxation (µSR) in KV 3 Sb 5 [24] and CsV 3 Sb 5 [25], and by Kerr effect measurements in CsV 3 Sb 5 [26].…”

Large kagome family candidates with topological superconductivity and charge density waves

“…The exotic CDW states without electron-phonon coupling (EPC) mechanism [9] display many unconventional characteristics. The CDWs in these three compounds exhibit chiral anisotropy [11][12][13] and reduce the density of electronic states near the Fermi level [11,[14][15][16]. Various evidence including giant anomalous Hall response even without magnetic field [17,18], the chirality of CDW that can be tuned by a magnetic field [11][12][13], edge supercurrent [19] and spontaneous internal magnetic field [20] indicates that the charge order may break the time-reversal symmetry, which has also been verified theoretically [11,21,22].…”

“…The CDWs in these three compounds exhibit chiral anisotropy [11][12][13] and reduce the density of electronic states near the Fermi level [11,[14][15][16]. Various evidence including giant anomalous Hall response even without magnetic field [17,18], the chirality of CDW that can be tuned by a magnetic field [11][12][13], edge supercurrent [19] and spontaneous internal magnetic field [20] indicates that the charge order may break the time-reversal symmetry, which has also been verified theoretically [11,21,22]. Moreover, it has been found that CsV 3 Sb 5 samples have the roton pair density wave [7], which is analogous to the one in unconventional high-T c cuprate superconductors [23].…”

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

“…One of the key features of the AV 3 Sb 5 family is the formation of a density-wave state accompanied by a superstructure [9]. While there is a consensus on the 2 × 2 in-plane modulation [22,[41][42][43][44][45], both two-fold and fourfold modulations along the c axis have been proposed [23,44,46,47]. This superstructure formation is concomitant with the reduction in the density of states at the Fermi level.…”