Spin Gaps and Bilayer Coupling in YBa$_2$Cu$_3$O$_{7-δ}$ and YBa$_2$Cu$_4$O$_8$

A. J. Millis; H. Monien

doi:10.1103/PhysRevB.50.16606

paper

Spin Gaps and Bilayer Coupling in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ and YBa $_{2}$ Cu $_{4}$ O $_{8}$

arXiv:cond-mat/9311035 · doi:10.1103/PhysRevB.50.16606

Abstract

We investigate the relevance to the physics of underdoped YBa $_{2}$ Cu $_{3}$ O $_{6 + x}$ and YBa $_{2}$ Cu $_{4}$ O $_{8}$ of the quantum critical point which occurs in a model of two antiferromagnetically coupled planes of antiferromagnetically correlated spins. We use a Schwinger boson mean field theory and a scaling analysis to obtain the phase diagram of the model and the temperature and frequency dependence of various susceptibilities and relaxation rates. We distinguish between a low $ω, T$ coupled-planes regime in which the optic spin excitations are frozen out and a high $ω, T$ decoupled-planes regime in which the two planes fluctuate independently. In the coupled-planes regime the yttrium nuclear relaxation rate at low temperatures is larger relative to the copper and oxygen rates than would be naively expected in a model of uncorrelated planes. Available data suggest that in YBa $_{2}$ Cu $_{4}$ O $_{8}$ the crossover from the coupled to the decoupled planes regime occurs at $T 700 K$ or $T \sim 200 K$ . The predicted correlation length is of order 6 lattice constants at $T = 200 K$ . Experimental data related to the antiferromagnetic susceptibility of YBa $_{2}$ Cu $_{4}$ O $_{8}$ may be made consistent with the theory, but available data for the uniform susceptibility are inconsistent with the theory.

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Spin Gaps and Bilayer Coupling in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ and YBa $_{2}$ Cu $_{4}$ O $_{8}$

Abstract

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Spin Gaps and Bilayer Coupling in YBa2​Cu3​O7−δ​ and YBa2​Cu4​O8​

Abstract

References in corpus (8)

Cited by in corpus (30)

Spin Gaps and Bilayer Coupling in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ and YBa $_{2}$ Cu $_{4}$ O $_{8}$