Spin dynamics in a doped-Mott-insulator superconductor

Abstract

We present a systematic study of spin dynamics in a superconducting ground state, which itself is a doped-Mott-insulator and can correctly reduce to an antiferromagnetic (AF) state at half-filling with an AF long-range order (AFLRO). Such a doped Mott insulator is described by a mean-field theory based on the phase string formulation of the t-J model. We show that the spin wave excitation in the AFLRO state at half-filling evolves into a resonancelike peak at a finite energy in the superconducting state, which is located around the AF wave vectors. The width of such a resonancelike peak in momentum space decides a spin correlation length scale which is inversely proportional to the square root of doping concentration, while the energy of the resonancelike peak scales linearly with the doping concentration at low doping. An important prediction of the theory is that, while the total spin sum rule is satisfied at different doping concentrations, the weight of the resonancelike peak does not vanish, but is continuously saturated to the weight of the AFLRO at zero-doping limit. Besides the low-energy resonancelike peak, we also show that the high-energy excitations still track the spin wave dispersion in momentum space, contributing to a significant portion of the total spin sum rule. The fluctuational effect beyond the mean-field theory is also examined, which is related to the broadening of the resonancelike peak in energy space. In particular, we discuss the incommensurability of the spin dynamics by pointing out that its visibility is strongly tied to the low-energy fluctuations below the resonancelike peak. We finally investigate the interlayer coupling effect on the spin dynamics as a function of doping, by considering a bilayer system.

24 pages, 17 figures, revised version to appear in Phys. Rev. B

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• Evidence for decay of spin-waves above the pseudogap in underdoped YBa2Cu3O6.35
• Lower Pseudogap Phase: A Spin/Vortex Liquid State
• Spin-roton excitations in the cuprate superconductors
• Mutual Chern-Simons Theory of Spontaneous Vortex Phase
• Bosonic resonating valence bond wave function for doped Mott insulators
• Crossover from Fermi Arc to Full Fermi Surface
• Microscopic origin of local moments in a zinc-doped high-$T_c$ superconductor
• Charge dynamics in the phase string model for high-Tc superconductors
• Thermal Hall Effect and Neutral Spinons in a Doped Mott Insulator
• Excitons in QED3 and spin response in a phase-fluctuating d-wave superconductor
• Electric transport in doped Mott insulators dictated by a non-Ioffe-Larkin composition rule and spinons
• Intrinsic phase fluctuation and superfluid density in doped Mott insulators
• Effect of phase string on single-hole dynamics in the two-leg Hubbard ladder