Bilayer spin dynamics in underdoped YBa2Cu3O6+x

The bilayer structure of YBa2Cu3O6+x supports spin excitations that are eit her even or odd under a symmetry operation that exchanges two directly adja cent CuO2 layers. Both types of excitation have been observed in underdoped YBa2Cu3O6+x by inelastic neutron scattering. Even and odd response functio ns are split in energy. The temperature evolution in the normal state is pa rallel in both channels, but different behavior is observed in the supercon ducting state where a resonant enhancement is observed only in the odd chan nel. The measurements shed new light on the nature of interlayer interactio ns in the cuprates. (C) 1998 Elsevier Science Ltd. All rights reserved.