Investigation of possible supersolid behaviour in a 4He crystal
Superfluidity and Superconductivity are phenomena of central importance in physics, and form the subject of ten Nobel prizes. Helium is the only material to remain liquid down to the absolute zero of temperature. Below 2.17K liquid 4He becomes a superfluid, and is able to flow with no apparent resistance. This phenomenon has its origin in Bose Einstein Condensation (BEC) of the 4He atoms (which are bosons!) More recently BEC has been observed in metastable dilute alkali gases of bosonic atoms. This state exhibits macroscopic quantum coherence; the entire system is described by a single macroscopic wavefunction, with the consequence that its flow properties are subject to the laws of quantum mechanics.
It was proposed as long ago as 1970 by Anthony Leggett (Nobel Laureate 2003) that solid 4He might also exhibit non-classical flow properties – referred to as supersolid behavior . Recent experiments by Kim and Chan claim to observe this supersolid behaviour . These are striking results and if confirmed of great significance [3,4]. This project will involve the use of torsional oscillator techniques to investigate the possible new supersolid phase, its dependence on crystal quality, geometry and pressure. In addition we plan to investigate the role of 3He impurities on the transition by nuclear magnetic resonance techniques.
This project offers the opportunity to work on experimental fundamental condensed matter physics in an exciting area. The group has good links with several theoretical and experimental groups in Europe and the USA, providing opportunities for further research training.
 A J Leggett, Phys. Rev. Lett. 25, 1543 (1970)
 E Kim and M H W Chan, Nature, 225 (2004) and submitted to Science
For further information contact Professor Brian Cowan.