Evolution of Charge and Pair Density Modulations in Overdoped Bi2Sr2CuO6+δ

Abstract

One of the central issues concerning the mechanism of high temperature superconductivity in cuprates is the nature of the ubiquitous charge order and its implications to superconductivity.Here we use scanning tunneling microscopy to investigate the evolution of charge order from the optimally doped to strongly overdoped Bi2Sr2CuO6+δ cuprates. We find that with increasing hole concentration, the long-range checkerboard order gradually evolves into short-range glassy patterns consisting of diluted charge puddles. Each charge puddle has a unidirectional nematic internal structure, and exhibits clear pair density modulations as revealed by the spatial variations of superconducting coherence peak and gap depth. Both the charge puddles and the nematicity vanish completely in the strongly overdoped non-superconducting regime, when another type of short-range order with √2 × √2 periodicity emerges. These results shed important new lights on the intricate interplay between the intertwined orders and the superconducting phase of cuprates.

Charge Order at High Temperature in Cuprate Superconductors

“…3(c)). CDF are therefore present also in proximity of the putative quantum critical point at p ≈ 0.19 connected to the pseudogap and in the overdoped regime, disappearing only -as confirmed by recent STM and Xray scattering experiments [51,67] -in extremely overdoped, non superconducting, samples. Ultimately, the low temperature charge density waves confined to relatively small regions of the cuprate phase diagram appear as atolls in the sea of ultra-short range charge modulations.…”

Cuprate superconductors as viewed through a striped lens

“…49 The observation of periodically-modulated Josephson tunneling demonstrates that the pairing correlations are spatially-modulated and in-phase with the CDW order [408]. Complementary work on Bi2201 shows that the coherence peaks in the superconducting state are modulated at the same period as the CDW in Bi2201 [409,410]. At minimum, these results indicate that the CDW order does not compete with pairing.…”

Compartmentalizing the cuprate strange metal

“…On a fundamental level, limiting low-T T -linear resistivity can only arise from scattering off bosonic fluctuations with a characteristic frequency Ω that is lower than the temperature scale [37]. While charge fluctuations and spin fluctuations have been extensively reported in overdoped cuprates [38][39][40][41][42][43], there is as yet no evidence that Ω Ñ 0 or that the correlation length of the associated order parameter diverges, neither at p ˚nor across the entire strange metal regime. This lack of an identifiable quasi-static bosonic mode has compelled theorists to look beyond conventional many-body approaches [44][45][46] and experimentalists to look beyond the zerofield resistivity [11,12,[47][48][49] for additional clues to the origin of strange metallic behavior.…”