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NHMFL High B/T Facility Gainesville, FL.
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NHMFL High B/T Facility Gainesville, FL.

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  1. NHMFL High B/T FacilityGainesville, FL. • ADVANCEMENTS 2009—2010 • I. INCREASED USER capacity • (a) Fast turnaround: 10 T, 10 mK capability (b) Initiated Use of BAY 2 (UF Microkelvin Lab.) • II. NEW INSTRUMENTATION • (a) Low temperature preamplifier • (b) High sensitivity dielectric gauge • In Progress: 20+ T MAGNET for Bay 3 • … under tests (Cryomagnetics Inc.) • NSF ARIR2 Award: Rebuild UF liquefier & recovery system • serves High B/T, AMRIS, Phys., Chem., Mat. Sci.

  2. HIGH B/T OPERATIONS MICROKELVIN LAB. & WILLIAMSON ANNEX < 2008: Bay 3 only 2009 --- added Bay 2 (part-time) > 2012 propose open Bay 1 to NHMFL users

  3. NHMFL High B/T FacilityFUTURE DIRECTIONS • I. Development of New Technologies (2011-12) • (a) High Pressure at Very Low T • ….. Extend parameter space for • (QPT, magnetization etc.) • ….. would be unique • (b) High Sensitivity Magnetometry • …… nano-engineered devices • (heavy fermions, half-metals, frustrated magnets…) • II. Upgrade Bay 2 (advance to full-time user use) • Add 16 T Magnet from Bay 3 (after commissioning 20 T – bay 3) • re-engineer dewar dil. fridge geometry) • III. Open Bay 1 to NHMFL use (2012-14)

  4. sample rotator heat exchanger High B/T: Unique Capabilities  Dedicated to high-B experiments requiring T< 20 mK & ultra-quiet environment &/or long coolingtime. B = 15.3/16.5 T ( upgrade to 20 T) Inhomogeneity 1.6x10-5 , 25 mm DSV experimental space.  Ultra-Low Temperature Tmin < 0.4 mK, 8 nW cooling power, t > 6 weeks @ 1 mK Ultra-low T Rotator angle dependence of FQHE High Sensitivity Pulsed NMR Low Temperature Preamplifier Crossed coil at T  0.1 K Sample finger at T  5 mK

  5. NMR Studies of Dilute 3He in Solid 4He at Very Low temperatures: Supersolid State D. Candela (Univ. of Massachusetts), S. S. Kim, C. Huan, L. Yin, J. S.Xia and N. Sullivan, University of Florida and NHMFL. Science Highlight 1 First experiment to probe microscopic dynamics of proposed supersolid helium NMR relaxation times measure atom-atom exchange rates: sensitive to changes in ground state and transition to supersolid Dramatic change in T1 for low 3He at supersolid transition: mimics change in elastic modulus low 3He conc. high 3He conc. Developed low temp. amplifier for enhanced NMR sensitivity S. S. Kim et al., J. Low Temp. Phys. 158, 584 (2010) Bay 3 Microkelvin Lab. Support: NHMFL UCGRP

  6. Science Highlight 2 Metal Monophosphonates M{(2‑C5H4NO)CH2PO3}(H2O)2 (M = Co, Ni, Mn, Cd): Synthesis, Structure, and Magnetism T .-H. Yang & L.-M. Zheng (Nanjing University) S. Gao (Peking University), M.W. Meisel et al. (Univ. of Florida) Conjecture: new series of spin ladders with tunable S spanning Quantum to Classical limits? Wm Hall Annex Co Ni Mn Result: weakly interacting dimer systems! Support: NSF/DMR Publication: T.-H Yang et al., Inorg. Chem. 49, 8474-8480 (2010)

  7. Anisotropic Disorder in Superfluid 3He: Effects of High Porosity Aerogel on the Superfluid Phases of 3He Yoonseok Lee, B.H. Moon, N. Masuhara, P. Bhupathi, M. Gonzalez, and M.W. Meisel,(UF); N. Mulders (U. of Delaware) Science Highlight 3 Bay 2 Microkelvin Lab. Direct propagation of ultrasound through aerogel/3He 1. P-T-B phase diagram of A-B transition 2. Investigating the spectrum of impurity states => analogous to tunneling in SC. PRB 82, 0605501(R) (2010) Editor’s Suggestion Solid lines: 3He in aerogel Broken lines: bulk behavior PRB 81, 134526 (2010) Conclusions: (i) aerogel presents random orbital field  similar effect as H. (ii) Impurity scattering reduces strong coupling effect. (iii) non-trivial spectrum of impurity states probably from the finite size of impurity (aerogel strands)

  8. Science Highlight 4 Charge Carrier Density Variation and Effects on 5/2 Fractional Quantum Hall Effect W. Pan (Sandia National Laboratories), D. Tsui (Princeton Univ.) N. Masuhara (University of Florida and NHMFL). Hetero-junction insulated gate field-effect transistor (HIGFET) ----- 2DEG density up to 4 X 1011 cm -2 , controlled by gate voltage Energy gap measurements over wide range of density of 2D electron gas ---- determine if n = 5/2 FQHE state is spin polarized or unpolarized ---- thermally activated 5/2 state observed for first time Bay 2 Microkelvin Lab. Temperature dependence and energy gap Magnetic field dependence Support: and Sandia National Laboratories & NHMFL. Sample supplied by L.N. Pfeiffer, K.W. Baldwin, and K.W. West.

  9. Dielectric Constant of Solid 4He: Supersolid Transition M.W. H. Chan (Penn. State Univ.); L. Yin, J.S Xia, C. Huan et al. (Univ. of Florida) Science Highlight 5 Dielectric Constant of Solid 4He: Supersolid Transition M.W. H. Chan (Penn. State Univ.); L. Yin, J.S Xia, C. Huan. (Univ. of Florida) Science Highlight 5 New high sensitivity gauge --- determine effect of transition on polarizability of solid 4He Results: Stiffening of lattice due to pinning of dislocations integral to supersolid behavior Wm Hall Annex Support: NSF/DMR Proceed. Qu. Fluids & Solids 2010

  10. Recent Experiments: 1. BEC and Quantum Phase Transitions in S=1 Antiferromagnet. V. Zapf (LANL) , A. Padhuan-Filho (Sao Paulo), Y. Lin (UF) et al. 2. Crossover from non-universal to universal scaling regime in quantum Hall plateau transition. W. Pan (Sandia Nat. Lab.) W. Li & D. Tsui (Princeton Univ.), J.S Xia (UF) et al. 3. Magnetic Interactions of Novel Materials at Low T/High B (2D quantum magnets). M.W. Meisel (UF), A. Feher et al. (Šafárik Univ., Košice, Slovakia).) 4. Dynamics of 3He Impurities in “Supersolid” 4He: NMR Studies D. Candela (Univ. Mass.), C. Huan (UF) et al. 5. Gapless anisotropic superfluids (3He in aerogel). Y. Lee et al. (U.F.) 6. Low temperature Magnetism Spin ladders: Metal monophosphates. T.-H Yang, L.-M. Zheng (Nanjing Univ.), S. Gao (Peking Univ.) , M. Meisel (UF) et al. 7. de Haas-van Alphen oscillations in CeCoIn5. S. R. Julian ( U. Toronto), A. McCollam (Nijmegen) 8. High sensitivity dielectric studies of supersolid 4He. M.W.H. Chan (Penn State U.), L. Yin, J.S. Xia (UF) 9. Search for Bose Glass States: Br doped DTN. V. Zapf (LANL) , A. Padhuan-Filho (Sao Paulo), Y. Lin (UF) et al.

  11. HIGHB/T CAPABILITIES: NMR Cell HIGH B/T Instruments: NMR Cell NMR up to 16 T : Studies of quantum diffusion of 3He in superfluid 4He for high nuclear spin polarization. Re-entrant cavity with walls at relatively high temperature and sample in cold finger inside cavity

  12. NEW CAPABILITIY: LOW TEMPERATURE AMPLIFIER HIGH B/T Instruments: NMR Cell Uses HEMT transistor (simple source follower) can operate to ~ 0.3 K T Noise ≤ 1 K

  13. Crossed-Coil NMR Probe: low frequency, low gamma S. S. Kim, C. Huan et al. unpublished Pulse B1, create transverse Magnetization in receiving coil

  14. sample rotator heat exchanger HIGH B/T CAPABILITIES: Ultra-Low T ROTATOR