High B/T Facility: Breakout Neil Sullivan 2014 Users Committee Meeting Tallahassee, FL October 10-11, 2014

High B/T Facility Unique High Field-Low Temperature Capabilities  Provide Users access to high fields and ultra-low temperatures, simultaneously in an ultra-quiet environment  Three stations for users 1990 Bay 2: B=8T, T min ~ 0.07 mK, homog. ~ /cm (open to NHMFL Users 2007) 1998 Bay 3: B=15/16.5T, T min ~ 0.4 mK, homogeneity 1.6x10 -5 /cm, 8 nW cooling power, t > 6 1 mK 2004 Annex: 10 T/40 mK -- fast turnaround test samples & cell design  Capabilities ultrasound, transport, heat capacity, NMR/NQR to 1100MHz, magnetic susceptibility, resistivity, dielectric susceptibility  Users work with staff for optimum design and automated data acq

Priorities, New Directions 1. Reduce length of queue for magnet time --- currently approx. 9 months 2. Improve staff support --- cell design and instrumentation requires close work with local staff 3. Expand parameter space --- increase B > 16.5 T Plan for HTS magnet (needs new location) 4. Advanced Low T instrumentation --- exploit low physical temperature

HIGH B/T OPERATIONS MICROKELVIN LAB. & WILLIAMSON ANNEX < 2007: Bay 3 only added Bay 2 (part-time) > 2015 plan to add HTS magnet

High B/T Physics AMRIS 700 m Remote Site (New Physics Building) High Bay Area Need additional staff and instrumentation High B/T site New Physics Building

Top View Physics High Bay HTS Magnet Example 3 ft

Facility Stats Overview Facility Statistics  18 users: 8 users on-site for experiment, 10 present only for set-up 6% of on site users were students or postdocs 94% were senior personnel Research area all condensed matter physics  834 magnet days available to users -- 95% to external users  133% subscription rate 25% of proposals declined/deferred Operation Mode  1-2 user groups on-site each week  Superconducting magnets run 24/7 for 35 weeks /year set-up ~ 10 weeks per year maintenance ~ 7 weeks per year

Research Areas High B/T Facility Growth: Typical experiment: 1 PI, 2.5 Co-PIs 1 local collaborator, 1 sample maker 1 sample characterization 0.5 postdoctoral fellow, 0.5 graduate student. Fabrication of sample mount Lasts 6-18 months (varies widely) Uses liters liq. He Origin PIs Helium costs ($1k) Funding ($10k) No. Users Publications Opened Bay 2 + Annex

High B/T User Science Science Driver: Condensed Matter: FQHE: 2DES Quantum Hall Effect in Second Landau Level Recent progress in fabrication of high-quality low-density samples allows one to probe exotic quantum Hall states such as the =5/2 and 7/2 states a new regime where the electron-electron interactions are strong. New Low Temperature Results First observation of anisotropic transport for = 7/2 in a high-quality dilute (n=5x10 10 cm -2 ) 2D electron system. New behavior attributed to a large Landau level mixing effect that perturbs the pairing stability of composite limit. upturn in the energy gap seen for n < 5x10 10 cm -2, spin unpolarized ground state Competing quantum Hall phases: Second Landau Level of 2D Electron Systems W. Pan (Sandia), D. C. Tsui, K. W. Baldwin, K. W. West, L. N. Pfeiffer (Princeton Univ.) A. Serafin, L. Yin, J. S. Xia ( Univ. Florida) Phys. Rev. B 89, (R) (2014). Competing quantum Hall phases in the second Landau level in the low-density limit

Search for quantum Wigner solid and phase transition to liquid state in a dilute 2D hole GaAs quantum well. Plots of magnetoresistivity at 4mK. Density p in units of /cm 2. The dash line illustrates the evolution/melting of 2D Wigner solid while increasing the density p. Results: observe an isotropic incipient Wigner solid in the liquid state! Support: NSF/DMR High B/T User Science Ultra-low Temperature Transport studies of Low Density Two-dimensional Hole System Xuan Gao (Case Western Reserve University), G. Boebinger, (NHMFL, Florida State University) A. Serafin, J. S. Xia, Liang Yin (Univ. of Florida) -- submitted to Nature Proposed phase diagram Science Driver: Condensed Matter: 2D electron systems

Bose Glass in Doped Quantum Magnet Results: New state: Bose glass for 12<B<17.5T & T < 250mK Nature 489,379 (2012) Novel equilibrium Bose fluid realized for quantum organic magnets in high B Disorder intro. in controlled manner (Br doping – stretch bond) High precision susceptibility measurements ( mK) allowed detection of critical exponents T. Roscilde (Lyon), A. Padhuan-Filho (Sao Paulo), R. Yu (Univ. Houston), S. Haas (Univ. So. Cal.), A. Steppke (Max Planck Inst., Dresden), V. Zapf (LANL), L. Yin et al. (Florida) High B/T User Science Science Driver: Condensed Matter: BEC/Bose glass Bose glass and Mott glass of quasiparticles in a doped quantum magnet Ni(Cl 1–x Br x ) 2 ·4SC(NH 2 ) 2

AC magnetic susceptibility measurements new phases at low temperatures I.Quantum spin ice, T<140 mK II.Quantum kagome lattice T< 50 mK, H: 0.08 – 0.7 T Quantum Spin Ice: Pyrochlore Quantum Magnet Tb 2 Ti 2 O 7 New User Group Phys. Rev. Lett. 110, (2013). Supported by National Natural Science Foundation of China High B/T User Science Science Driver: Condensed Matter: frustrated magnetism Q. J. Li, X. F. Sun (Hefei National Lab., China), L. Yin, J. S. Xia, Y. Takano et al. (Univ. of Florida) Low-Temperature Low-Field Phases of the Pyrochlore Quantum Magnet Tb 2 Ti 2 O 7 Needed high sensitivity, low T susceptibility cell

High B/T Facility 0.05 mK + 8T vector magnet Weaknesses Long wait time in queue for magnet time after proposal acceptance --- cannot respond rapidly for users competing in “hot” areas Limited staff -- two supported by NHMFL, two by UF --- insufficient to operate robust user facility Competition Rapid growth of High B/T at Laboratory for Extreme Conditions (China) (considerable resources) Also Inst. Solid State Physics, (Vienna Univ. of Technology) Aging infrastructure (Tallahassee has helped in emergencies)

Strategic Goal: B> 30 T at sub-mK Expand Parameter Space Extend available B at ultra-low temperatures to T, would allow users to conduct experiments currently not possible elsewhere Examples of Need: 1. Determine critical behavior at BEC transitions 2. High-density high-quality fqHall samples (resolve questions exotic Hall states (5/2, 7/2) 3. A transitions in superfluid 3 He B> 15 T. Probes underlying physics of pairing symmetries relevant to HTS 4. High-field phase diagram nuclear spin ordering in solid 3 He Samulon et al. (2010) Ba 3 Mn 2 O 8 Nijmegen (2014) need LT data ? Remeijer et al. (1998)

High B/T Physics AMRIS 700 m Remote Site (New Physics Building) High Bay Area Need additional staff and instrumentation High B/T site New Physics Building

Ultrahigh Vacuum, Ultra Low Temperature and High Magnetic Field Scanning Probe Microscope Unisoku, 400mK with 9T/2T/2T vector magnets, in situ cleavage/deposition 2. International Center for Quantum Materials (Peking University) Xi Lin (Dan Tsui Laboratory) 1.Key Laboratory for Extreme Conditions (Chinese Academy of Science) Li Lu Nuclear Demagnetization Stage: 0.5 mK in 11T Electron temperatures In 2DES Competition: High Field/ Low Temperature Research Facilities

Research Experience for Undergraduates Robert Cumby (Bowdoin College): Super- regenerative Detectors for NQR detection, (Sullivan) Mathew W. Calkins (University of Florida): Implementation of a Differential Hall Element Magnetometer, (Meisel ). Maxwell Leonard (Illinois Wesleyan University): Magnetism of a Spin-1/2 Triangular-Lattice Heisenberg Antiferromagnet, (Takano) Science Quest UF rising 10 th graders live on campus for one week, perform science experiments, attend lectures Enhance Science Content Knowledge for K-8 Teachers: PROMiSE Program ( ) UFUTuRES Program ( ) (Hershfield and Meisel) Outreach Activities: Tours, Undergraduate Research, Local Schools