User Programs in DC Powered Magnets

1. User Programs in DC Powered Magnets Existing Facilities Science & Instrumentation Facility Improvements Presented by Bruce Brandt (NHMFL-Tallahassee)

2. In-house Scientists: Eric Palm (Low Temp. Physics) Xing Wei (Visible Optical Spectroscopy) Arneil Reyes (Condensed Matter NMR) Yong-Jie Wang (Far Infrared Spectroscopy) Stan Tozer (High Pressure) Scott Hannahs (Transport, Data Acquisition) Luis Balicas (Magnetic and Transport Measurements) Tim Murphy (Low Temp. Physics) Phil Kuhns (Condensed Matter NMR) Sergei Zvyagin (Sub/Millimeter Wave Spectroscopy) Alexei Souslov (Ultrasound Spectroscopy) Dmitri Smirnov (Far Infrared & Raman Spect.) Lloyd Engel (Microwave conductivity) NHMFL - DC Facility Superconducting, Resistive & Hybrid Magnets (32mm unless noted otherwise) 45T Hybrid with 30 mK Dil. Fridge Cell#10 Cell#4 Cell#6 Cell#8 Cell#14 Cell#2 Cell#12 mK Lab SCM1 18/20T DF SCM3 15T 10mK SCM2 18/20T 300mk-RT Large Cond. Test Cell 25T 52mm 12ppm 19.5T 195mm 30T 35T 33T 35T Low Temp. Dev. Lab. High Tc Wire Dev. *Ultrafast Pulse Optics *Sub/Millimeter Wave Spectroscopy *Dedicated Optics Cell *Lower Voltage Noise *New 3He Fridges Sweeper Mag Devpt Hybrid Cell#11 Cell#13 Cell#3 Cell#5 Cell#9 Cell#1 Cell#7 23T 50ppm 29T 50ppm 25T 50mm 32T 50mm Power Supp. Test Load 30T 35T 45T 48T Lasers Location Cryo Equp. 17T Optics

4. User Programs in DC Powered Magnets Existing Facilities Science & Instrumentation Facility Improvements Presented by Bruce Brandt (NHMFL-Tallahassee)

5. Science & Instrumentation: Angle-Dependent Magneto-Resistance Oscillations External User: Ardavan et al.; Oxford U. P. Goddard et al.; NHMFL - LANL The Angle Dependent Magnetoresistance Oscillations (AMRO) arising from the quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces of the layered organic superconductor (ET)2Cu(NCS)2 Review Paper Submitted

6. Science & Instrumentation: Magnetometry Figure 1 – Ni(tmdt)2 Torque Magnetometry Measurements of a Single-Component Molecular Metal to 33T External User: Tanaka et al. (AIST, Japan) Brooks et al. (NHMFL - FSU) A molecular metal1 was recently synthesized containing only Ni(tmdt)2 (see figure 1), where Tanaka, et al. had previously shown metallic character (rRT = 3 x 10-3 Wcm) with dR/dT > 0 to 0.6K. Using magnetic fields at the NHMFL DC facility and a microcantilever2, the de Haas van Alphen effect of this material was measured in temperatures as low as 0.5K. The sample stage consists of a piezoresistive-microcantilever (seenin figure 2) and a reference lever of nearly equal resistance. The dimensions of the cantilever (platform width ~ 50mm) and its high sensitivity make it ideally suited for small samples. Figure 3 clearly shows de Haas van Alphen quantum oscillations of Ni(tmdt)2 up to 32T, proving that this neutral molecular metal is indeed a metal with a Fermi surface. This is the first single component molecular material to unambiguously exhibit metallic character. The work is interesting in that it brings together the technology of nano-science (the AFM tip cantilever) with cutting edge molecular materials. 1H. Tanaka et al., Science 291, 285 (2001) 2E. Ohmichi et al., Rev. Sci. Instr. 73, 3022 (2002) 50 nN 100 mm dR/dF =0.5 W/mN Figure 3. The dHvA effect in Ni(tmdt)2 NSF-DMR -0203532 Figure 2 – Cantilever with sample mounted.

7. Science & Instrumentation: High Field/Frequency EMR Submillimeter Wave (140-700 GHz) Spectroscopy to 25T High-field magnetic excitations in the spin-Peierls material CuGe03+0.4%Si. ....from Dimerized to Incommensurate Phase S. Zvyagin and J. Krzystek (NHMFL), P. van Loosdrecht, A. Revcolevschi. Backward Wave Oscillator Typical ESR spectrum ESR frequency-field dependence and line-width behavior in CuGeO3+0.4%Si.

8. Science & Instrumentation: Ultrafast Optics Research External User: Kono; Rice Univ. Internal Users: Reitze; Univ. of Florida Stanton, Univ. of Florida Wei; NHMFL - FSU • Instrumentation at the NHMFL: • chirped pulse amplifier (CPA) • optical parametric amplifier (OPA) • Ti:sapphire laser • Capabilities • 150 fs time resolution, • time-resolved probing over 0.06–4.0eV energy scales • 4.2 – 300K, • up to 25T (50 mm wide-bore magnet) • Physics • magneto-exciton spectroscopy • “quantum optics” of excitons • quantum information science • spin relaxation characterization • novel coherent control methods in high fields

9. CW PL CPA PL Science & Instrumentation: Ultrafast Optics Research Observation of Bright-Dark Mixing of Magneto-Excitons - We have observed an anti-crossing behavior when a forbidden (“dark”) exciton state meets an allowed (“bright”) exciton state in undoped InGaAs quantum wells in high magnetic fields. The mixing between these states cannot be explained from valence band complexities. Rather, it is a manifestation of a new kind of Coulomb-interaction-induced mixed magneto-exciton states. Magneto-Photoluminescence from Highly Excited Quantum Wells - We have used the CPA and OPA for magneto-photoluminescence studies of undoped InGaAs quantum wells in high magnetic fields. Due to the extremely high intensities of the CPA and OPA, we are able to probe properties of highly energetic electron-hole pairs in quantizing magnetic fields. The figures to the right show both linear 632 nm (“CW PL”) and 775 nm fs-pumped (“CPA PL”) magneto-photoluminescence from undoped InGaAs quantum wells from 0 to 25T at the same average powers. The dramatic difference in the PL spectra and the appearance of multiple Landau levels in the CPA-pumped case may arise from the inability of hot carriers to relax and scatter during the pump pulse.

10. B Science & Instrumentation: Visible Optics Magneto-optics of single-walled carbon nanotubes to 45T S. Zaric, G. N. Ostojic, J. Kono, J. Shaver, V.C.Moore, M.S.Strano, R.H. Hauge, R. E. Smalley, X. Wei; Science 304:1129 (2004) Eg(0) ~ 1 eV DEAA ~ 45 meV at 45 T Linewidth ~ 30 meV kBT = 26 meV at 300 K Zeeman splitting ~ 5 meV at 45 T Polarizer D2O Monochromator / detector Lamp Probe Light SDS Quartz cell SWNT SDS (micelle) suspension

11. Science & Instrumentation: Visible Optics of SWNT Simulation Experiment • Peak positions calculated from Ajiki-Ando theory • Multiple Lorentzian peaks • Zeeman splitting with g = 2 included • ( 5.22 meV at 45 T) • Carrier population taken into account according to • Pi exp(-Ei/kT) (Boltzmann factor) • Incomplete magnetic alignment  angular distribution of nanotubes #1 #2 #1 • Magnetic alignment (induced large optical anisotropy) • 1st subband transitions show broadening and splitting • All PL peaks show significant redshifts with B • Simulation taking into account carrier population and angular distribution shows agreement  Evidence of AB phase 2pf/f0 in optical spectra of SWNTs

12. Science & Instrumentation: Ultrasound for DC & Pulse Fields Alexei Souslov, Al Migliori et al Pulse-echo transmission technique • Two ultrasonic techniques will allow one to study elastic properties of matter in magnetic fields near metamagnetic and phase transitions, for example. • These techniques provide information about the electron and magnetic systems of studied solids by revealing information about electron-phonon and magnon-phonon interactions • The combination of these ultrasonic techniques with other experimental methods will allow one to carry out acousto-optic or high hydrostatic pressure measurements in strong magnetic fields.

13. Development of ultrasonic pulse echo technique allows us to study angle dependencies of acoustomagnetic phenomena. For example, quantum oscillations in velocity of ultrasound, which are similar to de Haas - van Alphen effect. O. Svitelskiy, X. Zang, D. Shulyatev, A. Souslov

14. Magnetic field control of intersubband lifetime in MIR Quantum Cascade Lasers 27th International Conference on the Physics of Semiconductors O. Drachenko, J. Leotin, LNCMP, Toulouse D. Smirnov, A. Wade, NHMFL A. Vasanelli, C. Sirtori, Universite Paris VII & Thales 1 mm MIR QCL’s magneto-spectroscopy MIR QCLs @ strong magnetic field MIR QCLs @ NHMFL (in progress) ◊ AlGaAs , InGaAs l=8-11 mm, P<500mW (can be extended to 5-15 mm) ◊ QCL mount .. .. and probe Spectral measurements: first data taken with Bruker66 step-scan FTIR ◊ Intersubband magnetophonon resonance ◊ Pulsed current injection Dt ~ 1 ms, I < 3A ◊ Intersubband and phonon spectroscopy T=4-300K ◊ Measurements: ◊ Control of intersubband lifetime Voltage –Current vs B Light –Current vs B Spectroscopy – in progress

15. User Programs in DC Powered Magnets Existing Facilities Science & Instrumentation Facility Improvements Presented by Bruce Brandt (NHMFL-Tallahassee)

16. Facility Improvements: Some User Requests • NMR at highest fields of each magnet for more than an hour • A “second hybrid” to provide more running time at high fields • A dilution refrigerator in a 35 T magnet all the time and an NMR-friendly dilution refrigerator • Lower noise - measurements at the thermal noise limit should be our long term goal • Perennial Favorites: • More magnet time • Higher magnetic field • Larger sample space • Higher temperature furnaces • Lower temperature refrigerators • Ability to decide to extend a magnet run with no notice when everything is going well • More user support • Post Doc from user group stays at the NHMFL for long times - learns stuff, builds things • Collaborate on instrumentation development • Collaborate on measurement improvement • Collaborate on research

17. Facility Improvements: More Time at Highest Fields Transformer upgrade $1M Chiller upgrade $2.9M 45T 42T Repeat as budget allows 3hr 6hr 9hr 12hr 15hr 18hr 21hr 24hr Time • Crucial for experiments requiring long times at high field: • NMR of condensed matter systems, quadrupole nuclei • Heat capacity of heavy fermion systems • Phase transitions requiring temperature sweeps at fixed field • Materials processing • Required for optimal performance of the Series Connected Hybrid

18. Facility Improvements: Higher Fields & More Time Max. 7 hr Field 32 mm Bore FL Bitter Hybrid / SCH Elec. Power Cost Limit Imposed by Power Grid and Other NHMFL Loads 56MW / $6.3M 42T* 60T  / 44T 730 V, 20 kA ($0.3 M). All fields increase ~10% with NEW technology 48MW / $5.4M 38T 50+T / 42T 600 V, 20 kA ($1.9 M). Cooling capacity Increase ($3.1M) All fields increase 10% with existing technology “NMR” field increases by >18%. Run time at high field to ~8 hours. 40MW / $4.2M 35T 45T / 40T ~48T* 32MW / $3.6M 30T 41T / 34T New Technology *Repair outsert Transformers, Voltage increase Current Increase User Building 2006 2008 2010 2012 Year

19. Facility Improvements: Conceptual Schedule • Tasks completed to date: • Determine the limits to upgrading: • Existing power components • Existing cooling system • Options for higher power magnets • Costs of identified options • Scientific impact of identified options • Determine the path and schedule for upgrading November-December, 2004: Request proposals for transformers Request proposals for rectifier controls Design components needed to increase power supply voltage Request proposals for cooling system March through May 2006: Install new transformers, new control system, increased voltage Install expanded cooling system

20. Facility Improvements: Need for More Time

21. Options for Increased DC Powered Magnet Time With Existing Magnet Types Annual Cost $12.5M 15 hr / 7 day +$1.6 M/yr 22 hr / 7 day +$3.2 M/yr $9.3M $7.7M 15 hr / 5 days (now) Magnet Days per Week 4 8 12 16 20 24 28 32 36 With “10 MW” Hybrids And Improved Power Supplies $17.5M 22 hr / 7 day 4 Add SCH $12.7M 3 15 hr / 7 day 2 1 $9.6M $7.7M 15 hr / 5 days Magnet Days per Week 8 16 24 32 40 48 56 64 72

22. The DC User Program is doing very well • A strong group of user support scientists and technicians is studying a wide range of scientific problems, developing new measurements, and refining old ones. • Six to ten new user groups receive magnet time each year. • Continuing research groups are improving. • We have been given $7.5M by the State of Florida to provide new instrumentation and research space and to renew and improve the magnet power supplies and cooling systems.