Spatial Correlations in the Vortex Matter Systems
The study of vortices in superconductors, so-called vortex matter physics, has made important
contributions to aspects of statistical physics, classical correlations, order-disorder transitions andrelated phenomena, and has connections to other fields such as polymer and colloidal physics. In thecuprate superconductors the combination of high superconducting anisotropy, extreme type-IImaterials parameters (high " and low " ) and high temperatures gives rise to a whole zoo of exotic
vortex phases including vortex solids, vortex liquids and vortex glasses [1]. Many years ago we usedthe µSR technique [2] combined with small-angle neutron scattering [3] to probe local variations in
the order associated with vortex lattice melting and also with a disorder-induced transition to a vortex!
! behaviour was also later observed in the highly anisotropic
glass (VG) phase.
Similarsuperconducting organic BEDT charge transfer salts [4].
In recent years I have revisited this topic following the realisation that higher moments of the field
distributions derived from µSR experiments gives information on higher order spatial correlations of
the disordered vortex system [5]. In disordered systems scattering experiments reveal the structure
factor S(q) , related to pair-pair density correlations, but do not contain information on three bodycorrelations. From this perspective the vortex system becomes an interesting system in which to study
classical correlations, where three-body correlations are in general not easily accessible in the bulk ofsystem, although studies on colloids provide information at surfaces via real space observations. The! initial experiments were carried out the cuprate LSCO, chosen as an archetypical example of a systemof high but not extreme superconducting anisotropy. Here we showed that the vortex glass (VG) phase
could be shown to exhibit non-trivial three-body correlations that, under certain conditions of twobody disorder, give a unique signature of a negative third moment of the field distribution [5].
We have recently extended this analysis to a comprehensive study of the phase diagram of the highly
anisotropic cuprate BSCCO, and also BSCCO subject to irradiated with heavy ions to producerandomly distributed defects intended to disrupt spatial correlations. Earlier studies on irradiatedsamples had focussed only on two-body correlations [6,7], but here we make a complete survey ofquantities related two both two-body and three-body correlations in both the pristine and irradiatedmaterials. These results show some unexpected surprises, including changes in glassy order within theVG phase of the pristine material.
In the talk I will present a brief background to the topic of vortex matter, followed by a discussion oflargely unpublished new results on the local correlations of the vortex system in disordered phases asa function of field and temperature.
[1] G. Blatter et al., Rev. Mod. Phys. 66 1125 (1995).
[2] S.L. Lee, et al., Phys. Rev. Lett. 71 3862-3865 (1993).
[3] R. Cubitt et al., Nature 365 407-411 (1993).
[4] S.L. Lee, et al., Phys. Rev. Lett. 79 1563 (1997).
[5] R. Gilardi , et al., Phy. Rev. Lett. 88 217003 (2002).
[6] S.L. Lee, et al., Phys. Rev. Lett. 81 5209 (1998).
[7] F.Y. Ogrin et al., Physica B 289-290 355-359 (2000).

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