A-B Phase Conversion and Coexistence of Superfluid He in Aerogel

• Published in: Journal of low temperature physics 2008-02, Vol.150 (3-4), p.472-475
• Main Authors: Kado, R, Nakagawa, H, Obara, K, Yano, H, Ishikawa, O, Hata, T
• Format: Article
• Language: English
• ISSN: 0022-2291
• DOI: 10.1007/s10909-007-9582-8

We have studied phase transition of superfluid He at 2.4 MPa in cylindrical aerogel by NMR method. When the liquid is cooled down from the normal state, the A-like phase appears below superfluid transition temperature T c which is suppressed in comparison with the transition temperature of the bulk liquid. With further cooling below the certain temperature T ab,c , the A-like phase is converted into the B-like phase gradually. Both phases stably coexist within about 90 muK. When you keep the temperature constant in which both phases coexist, the A-B phase conversion stops. With furthermore cooling, the whole liquid becomes the B-like phase. The cwNMR spectra at the coexistence state suggest that the B-like phase is not uniformly distributed in the A-like phase like a large number of small bubbles in a liquid, but separated as a whole from the A-like phase. By applying a field gradient which changes as a function of square of radius, we found that the A-like phase is in the edge part with a cylindrical shape and the B-like phase is in the central part with a columnar shape.