Doug Osheroff

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Superfluid 3He A Unique Quantum System

Doug Osheroff
Les Houches
Stanford University NSF DMR 0305465
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Thanks go to many people Mike
Cross Peter Schiffer Hiroshi
Fukuyama Mike Hildreth (SLAC) Matt
OKeefe Yoonseok Lee Jim
Baumgardner Grace Mao Supported by
National Science Foundation DMR 9110423 and
9409590-004
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Superfluid B Phase Magnetic Susceptibility
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1950
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Homogeneous Nucleation Theory Consider
a sphere of stable phase within unstable phase
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Homogeneous Nucleation Theory Continued ? Put
in the numbers for 0.7TC ? AB 9.2?10-6
ergs/cm2 (FA FB) 0.13 ergs/cm2
Thus RC 1.45?m (compared to 40
Angstroms for water-ice) N 1010 atoms ?FMAX
3.4?106 kBT Nucleation Rate ?oe-3,400,000
B Phase should never
nucleate!
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Leggetts Baked Alaska Model (1984)

• Cosmic ray muon creates secondary electrons as it
  passes through superfluid.
• Electrons dump most heat per unit length just
  before they stop.
• Volume is warmed well above Tc.
• d) Near Tc the quasiparticles move
  ballistically, and form a hot expanding shell.
  Region inside shell cools rapidly to below Tc.
  This region must decide very quickly if it should
  be A or B phase.

If phase inside shell is B phase and survives
until its volume exceeds the critical volume, it
will continue to expand and fill the cell with
the low temperature phase, even after shell drops
below Tc.
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Detection of A-B Transition Time and Temperature

• A Temperature stable,
• bring in 60Co source.
• B Long tube nucleates
• in thermal equilibrium.
• C. Short tube nucleates in
• thermal equilibrium.

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Supercooled A Phase Lifetimes vs Temperature
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Comparison with Baked Alaska Model (BAM)
Within the BAM
Our data fits this form well, but not uniquely.
For example, a power of T would work as well as
Rcn. The best fit to the 60Co data is
Here Ro 0.45?m and
Here Heff (?A/?B)1/2 since the nucleation must
occur as constant M
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Magnetic Field Test of BAM
A severe test of the BAM can be made by
increasing the magnetic field. This will
increase Rc, and hence ?(T), in a manner which
should be accounted for by our equations.
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Superfluid 3He in Low Density Silica Aerogels To
study the effects of impurities on a clean
unconventional BCS state.
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NMR Frequency Shifts in Bulk Superfluid Phases
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Aerogel Structure
Aerogel, 98.2 Porous
Random, 98.2 Porous
350 nm
Courtesy Jeevak Parpia/Cornell
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Localized Spins

• Second layer ferromagnetic
• A 750 m2/g
• M M0 / (T q)
• Interferes with NMR
• Background
• Frequency Shifts
• Magnetic Scattering?
• Preplate with 4He!

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A-like Phase NMR-cooling
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A-like Phase NMR-cooling
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A-like Phase NMR-cooling
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A-like Phase NMR-cooling
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A-like Phase NMR-cooling
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A-like Phase NMR-cooling
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A-like Phase NMR-cooling
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Cooling Transition
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Cooling Transition
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Cooling Transition
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B-Phase NMR-warming
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B-Phase NMR-warming
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B-Phase NMR-warming
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B-Phase NMR-warming
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B-Phase NMR-warming
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B-Phase NMR-warming
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B-Phase NMR-warming
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Two Phases

• Similar to bulk
• Hysteresis between warming and cooling
• A-B transition on cooling
• A-B transition on warming?

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New Behavior
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New Behavior
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New Behavior

• B-phase on warming shows some A-like phase
  behavior
• Small negative frequency shift
• Excess magnetization, but still not the full
  A-phase value
• Part of sample is A-like phase?
• Warm into transition region, then cool to lower
  temperatures to investigate

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A Closer Look
Tc 2.381 mK
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A Closer Look
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A Closer Look
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A Closer Look
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A Closer Look
T 1.80 mK
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A Closer Look
T 1.80 mK
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A Closer Look
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A Closer Look
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A Closer Look

• Presence of A-like phase on warming
• Same A-like phase as on cooling
• A-B interface is strongly pinned, even near Tc
• B-phase NMR line looks bulk and sees
• the cell walls.
• Could not previously detect A-like phase
• What is the real transition temperature?

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The Equilibrium Transition

• Nuclear Dipole Interaction
• DwA (3gDg/5cAH) cos 2q
• DwB (3gDg/2cBH) sin2 f
• gD (ph2g2ltR2gt/2) y2
• Maximum Frequency Shift
• Assume A-like phase is ABM state
• Order Parameter Suppression
• DwmaxA,aero/DwmaxA,bulk (yA,aero/yA,bulk)2
• Is maximum meaningful?

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The Equilibrium Transition
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The Equilibrium Transition
99.4 Aerogel
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The Equilibrium Transition
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The Equilibrium Transition
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The Equilibrium Transition
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The Equilibrium Transition

• In Ginzburg-Landau Regime
• Ignoring sixth order terms in the order
  parameter
• F is proportional to y2
• Thus FB/FA 2/5 (DwBcB/DwAcA)
• B phase maximum NMR shift depends on
• magnetic field orientation only in terms of
  the
• textures produced. Always used a Pan-Am
  texture.

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The Equilibrium Transition
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The Equilibrium Transition
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The Equilibrium Transition
98.6 Porosity
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The Phase Diagram
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The Phase Diagram
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The Phase Diagram
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Conclusions

• 3He is a model BCS condensate
• Two phases, two symmetries
• New technique to probe phase diagram
• Pinning not an issue
• First phase diagram
• Different from the bulk
• New phase stabilized by aerogel

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The Planar State

• A Little Bit A
• Equal-Spin Pairing
• A Little Bit B
• J 0
• Decreases effect of scattering?
• Test by measuring WL

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