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Register a new userDevelopment of spin fluctuations under the presence of $d$-wave bond order in cuprate superconductors
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In cuprate superconductors, superconductivity appears below the CDW transition temperature $T_{CDW}$. However, many-body electronic states under the CDW order are still far from understood. Here, we study the development of the spin fluctuations under the presence of $d$-wave bond order (BO) with wavevector $q=(pi/2,0),(0,pi/2)$, which is derived from the paramagnon interference mechanism in recent theoretical studies. Based on the $4 times 1$ and $4 times 4$ cluster Hubbard models, the feedback effects between spin susceptibility and self-energy are calculated self-consistently by using the fluctuation-exchange (FLEX) approximation. It is found that the $d$-wave BO leads to a sizable suppression of the nuclear magnetic relaxation rate $1/T_1$. In contrast, the reduction in $T_c$ is small, since the static susceptibility $chi^s(Q_s)$ is affected by the BO just slightly. It is verified that the $d$-wave BO scenario is consistent with the experimental electronic properties below $T_{CDW}$.
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We show that, at weak to intermediate coupling, antiferromagnetic fluctuations enhance d-wave pairing correlations until, as one moves closer to half-filling, the antiferromagnetically-induced pseudogap begins to suppress the tendency to superconductivity. The accuracy of our approach is gauged by detailed comparisons with Quantum Monte Carlo simulations. The negative pressure dependence of Tc and the existence of photoemission hot spots in electron-doped cuprate superconductors find their natural explanation within this approach.
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We reveal the full energy-momentum structure of the pseudogap of underdoped high-Tc cuprate superconductors. Our combined theoretical and experimental analysis explains the spectral-weight suppression observed in the B2g Raman response at finite energies in terms of a pseudogap appearing in the single-electron excitation spectra above the Fermi level in the nodal direction of momentum space. This result suggests an s-wave pseudogap (which never closes in the energy-momentum space), distinct from the d-wave superconducting gap. Recent tunneling and photoemission experiments on underdoped cuprates also find a natural explanation within the s-wave-pseudogap scenario.
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