Condensed Matter Physics

“Big Facility” Physics in Grenoble

Sub Heading ESRF: X-rays ILL: neutrons

Big Facility Physics 26th Jan 2004

Condensed Matter Physics “Big Facility” Physics near Zurich - Paul Scherrer Institut S

m

S: muons SLS: X-rays

Big Facility Physics

SINQ: neutrons

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

Einzel lens Trigger Detector Einzel lens Mirror Velocity Spin Einzel lens (LN cooled) Moderator Entry scintillator Spin Velocity Low Energy (keV) muon beam Surface muon beam (K.E. = 4 MeV)

the muons come in <= HERE with 4 MeV energy and are spin polarised

Original apparatus designed and constructed by E. Morenzoni at Paul Scherrer Institut

Conical lens Positron telescopes Gate Valve Field direction at sample position Sample Cryostat

Condensed Matter Physics

muons are implanted in the sample surface <= HERE at a tuneable energy of 1 - 30 keV

Big Facility Physics 26th Jan 2004

Condensed Matter Physics

WHY USE (+ve) MUONS ?

•the spin-polarised

muon arrives in the sample

•its spin precesses

in the local B-field

•it decays, giving an

e + in about 2

m

s

•the e

+ tends to be emitted along the muon spin direction

Big Facility Physics 26th Jan 2004

Condensed Matter Physics

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) After implanting a large number of muons... =>

Big Facility Physics 26th Jan 2004

Condensed Matter Physics

The frequency of precession measures the magnetic field AT the muon ...

... which has been implanted at a known depth - controlled by its energy...

Big Facility Physics 26th Jan 2004

Condensed Matter Physics

Field

T.J. Jackson et al. Phys. Rev. Lett. 84, 4958-4961 (2000) increasing temperature

Distance below surface of YBCO First ever measurement of field profile on a nm scale just inside a superconductor

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

a new muon moderation cryostat - developed in Birmingham - and a new x 10 intensity muon beamline being developed at PSI

Big Facility Physics •micro-structured

superconductors

26th Jan 2004

Condensed Matter Physics Magnetic Flux Lines in superconductors Each flux line

Current Flux lines Motion

Carries a flux of

F

0 = h/2e

Big Facility Physics Current Type-II superconductor 26th Jan 2004

Condensed Matter Physics

T H

H H c2

normal state vortex vortex liquid F c Meissner state Liquid Plastic Smectic Moving Bragg glass

T T c

D=3 F 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 EPSRC – funded 11 T cryomagnet pattern from a

D

Diffraction Flux Lattice in niobium

Big Facility Physics 26th Jan 2004

Condensed Matter Physics Results from YBCO => Phys Rev Lett, Feb 2004 Four stretched triangular lattices at low fields

Big Facility Physics

B = 1 T pattern

26th Jan 2004

Condensed Matter Physics Results from YBCO => Phys Rev Lett, Feb 2004 Square lattice of flux lines at high fields Due to fourfold symmetry of d-wave flux line cores

Big Facility Physics

B = 11 T pattern

26th Jan 2004

Condensed Matter Physics Calculations of flux lattice structure and energy

lowest energy

s-wave: but forced to be square

Big Facility Physics

d-wave observed orientation d-wave: orientation rotated 45 deg

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-T c 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 Sr 3 Ru 2 O 7

Big Facility Physics 26th Jan 2004

Condensed Matter Physics Future Developments in neutron scattering S pallation N eutron S ource, 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

Big Facility Physics 26th Jan 2004

Condensed Matter Physics

Big Facility Physics 26th Jan 2004