Nature of Pure and Dirty Liquid 3He - Fundamental Investigations and Educational Activities

Yoonseok Lee (University of Florida) DMR-0239483

The effect of disorder on a many particle system is one of the most important and ubiquitous problems in condensed matter physics. We study the effect of controlled disorder in otherwise the purest condensed matter system, liquid 3He by utilizing nanometer scale porous medium, silica aerogel. Especially in the low milikelvin range, we can study the influence of disorder on unconventional (p-wave) superfluid 3He. We investigated this effect using 98% porosity silica aerogel in the presence of strong magnetic fields (up to 15 T) and discovered the third phase which has not been observed in this system [1]. We also observed significant modification in the phase diagram of this system compared with the pure system and propose the importance of anisotropic scattering in the system [2].

[1] H.C. Choi et al., Physical Review Letters 93, 145302 (2004) and [2] C.L. Vicente et al., Physical Review B (in press 2005).

Figure: Using high frequency transverse sound, the A-B transition of superfluid 3He in 98% porosity aerogel is investigated in the absence of magnetic field. Surprisingly, a narrow window of coexistence of the A and B phases is observed as indicated by the blue and red shaded bands. We propose that the anisotropic scattering provided by the strand-like structure of aerogel could play an important role on the nature of the A-B transition in dirty superfluid.

EDUCATION: Currently 3 graduate (Ph.D.) students are involved in this research, H.C. Choi, P. Bhupathi, and B. Moon. Total 7 undergraduate students are directly or indirectly involved in this research effort. Among them, 3 students participated through the REU program and two students (A. Gray and E. Calleja) graduated and are continuing their Ph.D work at UIUC and U. of Colorado, respectively. E. Calleja has presented his work at several professional meetings such as APS March meeting and International Conference on Ultra Low Temperature Physics. He won the first place in oral presentation competition at the 12th Florida-Georgia Louis Stokes Alliance for Minority Participation in Science and Technology and Engineering & Mathematics (Jan. 27–30, 2005).

Nature of Pure and Dirty Liquid 3He-Fundamental Investigations and Educational Activities

Yoonseok Lee (University of Florida) DMR-0239483

OUTREACH: PI host several laboratory tours of PI’s own Lab and the Microkelvin Laboratory of University of Florida as the Director of the facility through JSEHS, BioTRAC, and Science Quest Program. PI also gave 3 lectures and science demos for three 6th grade classes at the Kanapaha Middle School, Gainesville (Nov. 11, 2004). A high school student (Reza Sultan) from Canterbury High School, Ft. Myers participated in research in the PI’s group from June 12 to July 30, 2005 through Student Science Training Program at UF.

Research Opportunity For Undergraduates (ROFU)This program was initiated by the PI in 2003 to encourage undergraduate student research. About twice per semester, two or three faculty members are invited to give presentations on their research program and to describe potential projects for undergraduates. These lectures are followed by discussion and laboratory tours. According to the recent survey conducted by Undergraduate Physics (UP) News (student run newsletter in our Department), 37% of undergraduate students in our Department are involved in research in various forms. Since 2003, 22 faculty members were invited for 7 ROFU meetings.

Photo: Prof. Hill is giving a presentation at a ROFU meeting.