condensed matter physics big facility physics26th jan 2004 sub heading “big facility” physics in...
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Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Sub Heading
“Big Facility” Physics in Grenoble
ESRF: X-raysILL: neutrons
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
“Big Facility” Physics near Zurich
- Paul Scherrer InstitutSS: muons
SINQ: neutronsSLS: X-rays
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Low energy muons for investigation of:
Magnetic fields in thin films and surfaces
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
The apparatus for producing
a beam of low energy muons
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
muons are implanted in the sample surface<= HERE at a tuneable energy of 1 - 30 keV
the muons come in <= HERE with 4 MeVenergy and are spin-polarisedOriginal apparatus designed
and constructed by E. Morenzoni at Paul Scherrer Institut
F ie ld d irection at sam ple position
Sam ple C ryostat
Positronte lescopes
C onica llens
G ate Valve
TriggerD etector
E inzel lens Low Energy (keV)m uon beam
Spin
Surface m uon beam(K .E . = 4 M eV)
M oderator
M irror
E inzel lens(LN cooled)2
Einzel lens
Velocity
Spin
Velocity
Entry scin tilla tor
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
WHY USE (+ve) MUONS ?
•its spin precessesin the local B-field
•the e+ tends to be emitted along the
muon spin direction
•the spin-polarised muon arrives in the sample
•it decays, giving an e+ in about 2 s
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
After implanting a large number of muons... =>
The muon spin sweeps around like a lighthouse- the probability of an e+ arriving
at a fixed detector =>
oscillates (and decays) with time (after implantation)
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
... which has been implanted at a known depth - - controlled by its energy...
The frequency of precession measures the magnetic field AT the muon ...
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
First ever measurement of field profile on a nm scale just inside a superconductor
Field
Distance below surface of YBCO
T.J. Jackson et al. Phys. Rev. Lett. 84, 4958-4961 (2000)
increasing temperature
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Current Developments
new samples:
•low Tc super-conducting films
•ferromagnetic-normal and ferro-superconducting multilayers
•CMR+HighTc films
•micro-structured superconductors
- and a new x 10 intensity muon beamline being developed at PSI
a new muon moderation cryostat - developed in Birmingham
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Magnetic Flux Lines in superconductorsEach flux line
Carries a flux of 0 = h/2e
Flux lines
Current
Current
Type-II superconducto
r
Motion
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
F
T
H
Fc
Liquid
Moving Bragg glass
Smectic
PlasticVortex Glass
Bragg glass
D=3
Vortex Matter H -T Phase DiagramVortex Matter Dynamical Phase Diagram
H
T
normal state
vortex solid
vortex liquid
Hc2
Tc
Meissner state
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Detected by small-angle neutron diffraction SANS
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Diffraction pattern from
a Flux Lattice in
niobium
EPSRC – funded 11 T cryomagnet
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Results from YBCO => Phys Rev Lett, Feb 2004
B = 1 T pattern
Four stretche
d triangul
ar lattices
at low fields
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Results from YBCO => Phys Rev Lett, Feb 2004
B = 11 T pattern
Square lattice of flux lines at
high fields
Due to fourfold symmetry of d-
wave flux line cores
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Calculations of flux lattice structure and energy
s-wave: but forced to be square
d-wave: orientation rotated 45
deg
d-wave observed orientatio
n
lowest energy
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Future Work – mainly on “Vortex Matter”• flux lattice structures and pairing mechanisms in
unconventional superconductors
• flux lattice melting in low-Tc superconductors
• X-ray observation of flux line cores
• flux line motion and motion-induced ordering
• flux-line-like molecular structures
• Other neutron scattering, including inelastic neutron
scattering studies of fluctuations near QCP in Sr3Ru2O7
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
Future Developments in neutron scattering
Spallation Neutron Source, Oak Ridge USA
Big Facility Physics 26th Jan 2004
Condensed Matter Physics
European Spallation Source?
Probably in the UK
ILL will be competitive
for the next 10 years