Abstract

The concept of spin ladders originally appeared as a toy for theorists giving a simple model to study the interactions in the 2D Cu-O planes of high-T¬c superconductors. However due to some of the fascinating properties predicted by the theoretical work, and the fact that a growing number of materials showing a ladder structure have been synthesised, the study of ladder systems has evolved into a well established area of research in its own right. The possibility of finding novel superconducting phases in these compounds was predicted quite early on. However despite the discovery of superconductivity in the Sr0.4Ca13.6Cu24O41 system, and more recently in the AV6O15 family, relatively little experimental work has been done and the nature of the superconducting state remains a mystery. This lack of data is mainly due to experimental difficulties, as the superconducting phases appear only at high pressure, and the samples are extremely sensitive. I will present our results on the measurements of the upper critical field, and the phase diagram of the superconducting and anti-ferromagnetic phases, as well as some other recent experimental and theoretical studies, and discuss the implications for superconductivity. Clearly we are still a long way from understanding these systems and the next steps will require new experimental techniques. I will present a new experimental development which allows pressurizing larger samples in a liquid medium up to high enough pressures to study these systems, and should allow a new step forward.