1. Nature of Pure and Dirty Liquid 3 He - 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 3 He 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 3 He. We investigate this effect in 98% porosity silica aerogel using a high frequency sound of 9.5 MHz. We found that the sound attenuation shows drastically different behavior from the pure superfluid, e.g. substantially large zero temperature attenuation, non- exponential T-dependence, and absence of the order parameter collective modes, which suggest gapless superfluidity in this system. An ultrasound pulse is generated by a transmitter (speaker) and detected by a receiver (microphone) which are 3 mm apart. This plot shows the response of the microphone in time after a sound pulse is generated. At high temperatures, only the sound pulse made the trip from the speaker to the microphone is strong enough to be heard (showing only one peak). In superfluid (below 2 mK), the attenuation is getting low enough to detect consecutive echoes (multiple peaks). From the width in time and relative peak height between the successive echoes, the velocity and the absolute attenuation can be determined.

2. EDUCATION: Currently 3 graduate (Ph.D.) students are involved in this research, H.C. Choi, P. Bhupathi, and B. Moon. In the PI’s group, one graduate student and one undergraduate student conduct research as a team on a common project. Total 9 undergraduate students are/have been involved in this research effort. Among them, 3 students participated through the REU program and three students (A. Gray, E. Calleja, and S. Korenblit) graduated and are continuing their Ph.D work in Physics at UIUC, U. of Colorado, and U. of Michigan, respectively. Simcha Korenblit presented his work at professional meetings, APS March meeting and SESAPS meeting. Nature of Pure and Dirty Liquid 3 He-Fundamental Investigations and Educational Activities Yoonseok Lee (University of Florida) DMR-0239483 OUTREACH: PI hosts several laboratory tours of PI’s own Lab and the Microkelvin Laboratory of University of Florida as the Director of the facility (e.g. through the Science Quest Program at UF). PI also gave 3 lectures and science demos for three 6 th grade classes at the Kanapaha Middle School, Gainesville (Oct. 31, 2005) and participated in local high school science fairs as a judge (Lincoln Middle School and Hawthorne High School). UNDERGRADUATE RESEARCH (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 (2005 Spring) 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, 26 faculty members were invited for 9 ROFU meetings. UF SPS hosted Zone 4, 5, 6, 8, and 10 joint meeting in Nov. 2005. About 60 students and advisors came from 12 institutions. Students are performing a science demo jointly..