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+{\delta} 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 root2 * root2 periodicity emerges. These results shed important new lights on the intricate interplay between the intertwined orders and the superconducting phase of cuprates.
Highlights
A key characteristic of the cuprate high-temperature superconductors is the strong tendency for the charge carriers to form symmetry-breaking ordered states [1]
Our systematic scanning tunneling microscopy (STM) studies on Bi-2201 cover a broad range of phase diagrams from the optimally doped to overdoped non-SC regimes [Fig. 5(a)], which is much less explored compared to the underdoped regime
The quantitative analysis of the overall dI=dV line shape enables us to extract the characteristic features that are selectively sensitive to local superconductivity, and the correlation analysis between various spatial patterns reveals the relationship between the intertwined orders
Summary
A key characteristic of the cuprate high-temperature superconductors is the strong tendency for the charge carriers to form symmetry-breaking ordered states [1]. It remains unknown when and how the checkerboard order eventually vanishes in the strongly overdoped regime Another important recent progress is the observation that the charge order is closely related to the pair density wave (PDW) order [24,25,26,27,28,29], i.e., a periodic modulation of the Cooper pairing amplitude. The unidirectional stripelike internal structure of the charge puddle pervades the entire superconducting (SC) phase and exhibit clear PDW features as revealed by the spatial variations of the SC coherence peak and gap depth Both the charge puddles and the intrapuddle structure vanish completely in the strongly overdoped nonSpCffiffi regpimffiffi e, when another type of short-range order with 2 × 2 periodicity emerges. The STM topography is taken in the constant current mode with an electrochemically etched tungsten tip calibrated on a clean Au(111) surface [35], and dI=dV spectra are collected by using a standard lock-in technique with a modulation bias voltage with frequency f 1⁄4 423 Hz and 3 mV rms amplitude
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