Direct observation of charge order in underdoped and optimally doped Bi2(Sr,La)2CuO6+δ

Abstract

Charge order in underdoped and optimally doped high-Tc superconductors Bi2Sr2−xLaxCuO 6+δ (Bi2201) is investigated by Cu L3 edge resonant inelastic x-ray scattering (RIXS). We have directly observed charge density modulation in the optimally doped Bi2201 at momentum transfer Q 0.23 rlu, with smaller intensity and correlation length with respect to the underdoped sample. This demonstrates the short-range charge order in Bi2201 persists up to optimal doping, as in other hole-doped cuprates. We explored the nodal (diagonal) direction and found no charge order peak, confirming that charge order modulates only along the Cu-O bond directions. We measured the out-of-plane dependence of charge order, finding a flat response and no maxima at half integer L values. This suggests there is no out-of-plane phase correlation in single layer Bi2201, at variance from YBa2Cu3O6+x and La2−x(Ba,Sr)xCuO4. Combining our results with data from the literature we assess that charge order in Bi2201 exists in a large doping range across the phase diagram, i.e. 0.07 p 0.16, demonstrating thereby that it is intimately entangled with the antiferromagnetic background, the pseudogap and superconductivity.

Density Wave Probes Cuprate Quantum Phase Transition

“…3 a-c to d-f reveals that the dFF DW exhibits distinct evolutions for small and large spectral gap regions. From 16 meV to 48 meV, Q DW increases from 0.15 to 0.23 r.l.u., matching the change in wavevector that has been measured by resonant x-ray techniques from p ≈ 0.20 to near-optimal doping [22,26,27] and consistent with an evolving incommensurate wavevector. However from ∆ ≈ 50 meV to ∆ ≈ 85 meV, no significant increase is observed (Fig.…”

“…With increasing p at low temperature, the appearance of sharp antinodal quasiparticles (insets), indicative of a large normal state Fermi surface, occurs just below optimal doping (dashed line [21]), while the spectral gap persists into overdoped compounds (blue shading, with boundary marking the closing of the gap, as measured by ARPES [24] and NMR [25]). The data points mark existing sample-average measurements of the charge modulation wavevector,QDW, in Bi2201 from x-ray scattering (green [22], blue [26] and black [27] open symbols) and STM (blue [26], orange [28] and purple [30] filled symbols). Red triangles and circles are the sample-average measurements of the d-form factor charge modulations in the x and y directions, respectively, from this work, with p determined from Ando's conversion [31], as described in the Supplemental Material.…”

Emergent superconductivity upon disordering a charge density wave ground state

“…One common feature of nearly all unconventional superconductors is that the superconductivity coexists and competes with other symmetry broken states in a wide range of parameter space. These include the charge orders [1][2][3][4][5][6] and antiferromagnetism [7][8][9] in cuprtate superconductors, spin density waves in pnictides [10][11][12][13], orbital order in Ruthenates [14][15][16], among others. Often, the symmetry unbroken state is accessed via these competing ordered states upon destruction of superconductivity.…”

Dual structure in the charge excitation spectrum of electron-doped cuprates

“…The origin of the charge order (CO), originally observed in underdoped hole-doped cuprates (h-cuprates) [1][2][3][4][5][6][7][8][9][10][11][12][13][14] , is an active topic in condensed matter physics. The recent xray experiments for electron-doped cuprates (e-cuprates) 15,16 push the field even further.…”