3/21/2011
NHMFL HIGH B/T FACILITY
Part of the Microkelvin Research Lab
MicroKelvin Research Laboratory
 Scientific Mission
Dedicated to high-B experiments requiring T< 20 mK
Experiments generally require ultra-quiet environment
8 T Nuclear-Demagnetization Magnet
• Three compensated field regions for the heat switch and
thermometers. A fourth compensated region minimizes eddycurrent heating in the silver thermal link to the high-field region,
when the field is ramped down to cool the nuclear refrigerants.
Exterior of the building. The magnets and the main parts of
the cryostats are located below the ground level.
15 T/17 T High-Field Magnet
• Wide homogeneous-field region accommodates a 3He meltingcurve thermometer and allows more than one experiment to be
set up at a time. It also minimizes eddy-current heating due to
the motion of the magnet relative to the experiments.
• Field decay rate of 4 ppm/hr in the persistent mode. This slow
decay rate is essential for operation of the nucleardemagnetization cooling stage.
BAY 3:
Present magnet system
Dedicated 100% to NHMFL users.
Maximum magnetic fields: 15 T/17 T. Minimum
temperature: 0.5 mK.
 Three stations for users
Bay 3: B=15/16.5T, Tmin ~ 0.4 mK,
homogeneity 1.6x10-5 /cm,
8 nW cooling power, t > 6 wks @ 1 mK
20+ Tesla Magnet Upgrade for Bay 3
Experiments are controlled via an optical link from
outside the shielded room which houses the cryostat and
the magnet. The shielded room protects the experiments
from electromagnetic interferences (TV and radio waves,
emissions from computer monitors, fluorescent lights,
motors, etc.) , which can dump as much as 100 pW of
heat. No cell phones are allowed in the building.
Bay 2: B=8T, Tmin ~ 0.04 mK, homog. ~ 10-4 /cm
cm
140
130
H eat Switch
120
Zero Field Space
110
Top Load Access
Annex: 10 T/10 mK -- fast turnaround, test samples & cell design
New 8 T Nuclear Demagnetization Magnet
100
90
80
sampl
e
PrNi5
8 T Magnet
• Re-designed compensation windings to cope with the fringe
fields from the new 18 T/20+ high-field magnet.
70
60
50
rot
ato
r
heat exchanger
Therm al Link
40
3He,
Experiments are immersed in liquid
which is cooled
by demagnetization of the PrNi5-copper combo nuclear
stage. Cooling samples to 1 mK and below requires
technical expertise, meticulous attention to details, and
patience.
Pending the NSF funding renewal, this
bay will be offered 100% to NHMFL users to
reduce the ever growing waiting list for a magnet
time. Maximum magnetic field: 8 T. Minimum
temperature: 42 μK.
10
0
NMR/NQR to 1100MHz, ultrasound, transport, heat capacity
magnetic susceptibility, resistivity, dielectric susceptibility
Key Features of the New 18 T/20+ T Magnet
30
20
BAY 2:
 Capabilities
18/20 T M agnet
-10
-20
-30
New magnet system funded by
the State of Florida
• Higher magnetic field will facilitate studies of new physical
phenomena: highly polarized Fermi liquids, Bose-Einstein
condensation of nuclear-spin magnons in solid 3He, etc.
• Field decay rate of 0.4 ppm/hr in the persistent mode. This
improved rate will allow the magnet to be disconnected from the
power supply for up to one week, reducing electromagnetic
interferences and associated heat leak to the experiments.
 Users work with staff for optimum design and automated data acq.
Physics Low Temp Complex
MICROKELVIN LAB. & WILLIAMSON ANNEX
NHMFL High B/T
Main Cryostat
High B/T: Unique Capabilities
What’s New?
 Dedicated to high‐B experiments requiring T< 20 mK
& ultra‐quiet environment &/or long cooling time.
I. Development of New Technologies (2011‐12)
B = 15.3/16.5 T ( upgrade to 20 T)
Inhomogeneity 1.6x10‐5 , 25 mm DSV experimental space.
(a) High Pressure at Very Low T
….. Extend parameter space for
(QPT, magnetization etc.)
….. would be unique
 Ultra‐Low Temperature
Tmin < 0.4 mK, 8 nW cooling power, t > 6 weeks @ 1 mK
(b) High Sensitivity Magnetometry
…… nano‐engineered devices
(heavy fermions, half‐metals, frustrated magnets…)
II. Upgrade Bay 2 (advance to full‐time user use)
Ultra‐low T
Rotator
sample
angle dependence Low
Temperature
of FQHE
Preamplifier
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)
High Sensitivity
Pulsed NMR
heat
exchanger
rotator
Crossed coil
at T  0.1 K
Sample finger
at T  5 mK
1
3/21/2011
NMR Studies of Dilute 3He in Solid 4He
at Very Low temperatures: Supersolid State
Metal Monophosphonates M{(2‐C5H4NO)CH2PO3}(H2O)2
(M = Co, Ni, Mn, Cd): Synthesis, Structure, and Magnetism
D. Candela (Univ. of Massachusetts), S. S. Kim, C. Huan,
L. Yin, J. S.Xia and N. Sullivan, University of Florida and NHMFL.
T .‐H. Yang & L.‐M. Zheng (Nanjing University)
S. Gao (Peking University), M.W. Meisel et al. (Univ. of Florida)
low 3He conc.
NMR relaxation times measure atom‐atom
exchange rates: sensitive to changes in ground state
and transition to supersolid
Conjecture: new series of spin
ladders with tunable S spanning
Quantum to Classical limits?
0.4
6
0.3
Wm Hall
Annex
6
0.3
4
4
0.2
0.1
0.0
2
(1)
0.1
0
10
20
30
40
2
0
50
 (emu/mol)
0.0
Dramatic change in T1 for low 3He at supersolid
transition: mimics change in elastic modulus
high 3He conc.
0
3
0.2
3
2
0.2
2
0.1
0.1
1
(2)
0.0
0
10
1
20
30
40
0
50
0.0
Ni
0
0.6
8
0.6
Developed low temp.
amplifier for enhanced
NMR sensitivity
Co
0.4
0.2
T (emu K/mol)
First experiment to probe microscopic dynamics of
proposed supersolid helium
0.4
8
4
0.2
0.2
0.0
(3)
50
0
100
10
4
2
20
30
40
0
50
0.0
0
Mn
6
6
0.4
Result: weakly interacting dimer systems!
150
200
250
2
0
300
T (K)
S. S. Kim et al., J. Low Temp.
Phys. 158, 584 (2010)
Bay 3
Microkelvin Lab.
Publication: T.‐H Yang et al.,
Inorg. Chem. 49, 8474‐8480 (2010)
Support: NHMFL UCGRP
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)
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 sp[in polarized or unpolarized
‐‐‐‐ thermally activated 5/2 state observed for first time
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)
Support: NSF/DMR
Editor’s Suggestion
Temperature dependence and energy gap
Bay 2
Microkelvin Lab.
Bay 2
Microkelvin
Lab.
Magnetic field dependence
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)
Constant Constant
of Solid 4He: of Solid 4He:
Science Highlight 5Dielectric
Dielectric
Supersolid Transition
Supersolid Transition
M.W. H. Chan (Penn. State Univ.);
J.S Xia,
C. HuanState
et al. (Univ.
of Florida)
M.W.L.H.Yin,Chan
(Penn.
Univ.);
L. Yin, J.S Xia, C. Huan. (Univ. of Florida)
New high sensitivity gauge
Support: and Sandia National Laboratories & NHMFL.
Sample supplied by L.N. Pfeiffer, K.W. Baldwin, and K.W. West.
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).)
‐‐‐ determine effect of transition
on polarizability of solid 4He
4. Dynamics of 3He Impurities in “Supersolid” 4He: NMR Studies
D. Candela (Univ. Mass.), C. Huan (UF) et al.
Results: Stiffening of lattice due to pinning
of dislocations integral to supersolid behavior
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)
Wm Hall
Annex
8. High sensitivity dielectric studies of supersolid 4He.
M.W.H. Chan (Penn State U.), L. Yin, J.S. Xia (UF)
Support: NSF/DMR
Proceed. Qu. Fluids & Solids 2010
9. Search for Bose Glass States: Br doped DTN.
V. Zapf (LANL) , A. Padhuan‐Filho (Sao Paulo), Y. Lin (UF) et al.
2
3/21/2011
In what year was the Microkelvin
Lab Begun?
A.
B.
C.
D.
E.
1976
1981
1986
1995
2000
3