Abstract
We present time-of-fight inelastic neutron scattering measurements of La1:965Ba0:035CuO4
(LBCO), a lightly doped member of the high temperature superconducting La-based cuprate family.
By using time-of-flight neutron instrumentation coupled with single crystal sample rotation we
obtain a four-dimensional data set (three Q and one energy) that is both comprehensive and spans a
large region of reciprocal space. Our measurements identify rich structure in the energy dependence
of the highly dispersive spin excitations, which are centered at equivalent ( 1/2 ; 1/2 ;L) wave-vectors. These structures correlate strongly with several crossings of the spin excitations with the lightly dispersive phonons found in this system. These e ects are signi cant and account for on the order of 25% of the total inelastic scattering for energies between 5 and 40meV at low jQj. Interestingly, this scattering also presents little or no L-dependence. As the phonons and dispersive spin excitations centred at equivalent ( 1/2 ; 1/2 ;L) wave-vectors are common to all members of La-based 214 copper oxides, we conclude such strong quasi-two dimensional scattering enhancements are likely to occur in all such 214 families of materials, including those concentrations corresponding to superconducting ground states. Such a phenomenon appears to be a fundamental characteristic of these materials and is potentially related to superconducting pairing.
