SOLID STATE PHYSICS

internalchildlikeInternet and Web Development

Nov 12, 2013 (3 years and 7 months ago)

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SOLID STATE PHYSICS

C. Vettier Institut Laue Langevin

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SOLID STATE PHYSICS

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SOLID STATE PHYSICS


Understanding of bulk properties


Ground states


Susceptibilities


Simplifying but consistent patterns


Characterisation of phase diagrams


Structures


Relevant external fields


Measure of fluctuations


Time and Space

²
Dynamical susceptibilty



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FRONTIERS IN SOLID STATE PHYSICS

Physics moves towards complexity


coupled degrees of freedom

low dimensionality

H. Ronnow et al., 2002

Electron charge, spin, orbit,
Lattice

Soliton modes in CuGeO
3

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FRONTIERS IN SOLID STATE PHYSICS

Biggest unsolved problems ?

plenty !

Self
-
organised complexity

Exotic superconductivity

Inhomogeneity

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FRONTIERS IN PHYSICS OF SOLIDS

Superconductivity

Discovery in 1911


in Leiden

Successful model in 1957
-

BCS

1986 Discovery of High T
c

systems

Cuprates materials

Bednorz & Müller



36 K, 90K and 130 K

Before mid
-
80’s

T
c

restricted to below 23 K

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FRONTIERS IN PHYSICS OF SOLIDS

Superconductivity

Challenge :

Nature of couplings remains puzzling

despite an extraordinary activity

Applications

magnetic resonance imaging

power transport

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SUPERCONDUCTIVITY

model : glue
-
ing of electrons

attraction through lattice modes BCS

k

m

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SUPERCONDUCTIVITY

exotic couplings


magnetism

Phonon wave

Magnetic

Exciton wave

electron

s
-
wave

pairs

d
-
wave

pairs

electron

P. Coleman, 2001

No consensus on a global model


despite tremendous efforts

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SUPERCONDUCTIVITY

Neutrons : unique and necessary tool

Use all possible methods

Structures and motions of particles

Separation of lattice and magnetic effects

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BCS superconductivity

MgB
2

T
c

~ 39 K

J. Nagamatsu et al., 2001

Mg

B

B

Resistivity

Temperature (K)

0 20 40 60 80 100

T
c

0 10 20 30 40 50 60

Temperature (K)

Susceptibility

T
c

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BCS superconductivity

Inelastic neutron scattering

R. Osborn et al., 2001

0 20 40 60 80 100

Energy (meV)

Phonon density of states

B
-

bond stretching modes

Mg

B layer


-
orbitals


-
orbitals

MgB
2


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BCS superconductivity

Aluminium doping destroys
superconductivity

Electron doping

Temperature

(K)

Susceptibility


Mg
1
-
x
Al
x
B
2

J.S. Slusky et al., 2001

Z
Mg

= 12

At. Weight
Mg

= 24.3

Z
AL

= 13

At. Weight
Al

= 27.0

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0 25 50 75 100 125 150

ENERGY (meV)

20


15


10


5


0

Phonon density of states

BCS superconductivity

B. Renker et al., 2002

Renormalisation of

phonon modes

Neutrons identify

key phonon modes

MgB
2

AlB
2

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BCS superconductivity

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BCS superconductivity

Vortex lattices


penetration depth


anisotropy

Small angle neutron scattering

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Ch. Dewhurst, B. Cubitt, 2002

SANS from Vortex Lattices
in MgB
2

Isotropic penetration depth

BCS superconductivity

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BCS superconductivity

Neutrons have unravelled the binding


mechanism in MgB
2

More neutrons are needed to discover


couplings in exotic superconductors

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Exotic superconductivity


Fluctuations

coupling of quasi
-

particles


Neutron scattering


effects of lattice,



electron spins and charges


Neutron polarisation


Dynamics is essential

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Superconducting
YBa
2
Cu
3
O
7


Non
-
superconducting
YBa
2
Cu
3
O
6

Exotic superconductivity

Cuprate oxides

Charge reservoir

Neutron diffraction

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Phase diagram

anomalous metal

doping

metal

temperature

HT
c

superconductors


cuprate oxides

FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

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Q
AF

FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Antiferromagnetic phase

Normal excitations : spin waves

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Antiferromagnetic phase

Superconducting phase

Doping

Q
AF

Q
AF

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

x=0.5
x=0.52
x=0.83
x=0.92
x=1
YBa
2
Cu
3
O
6+x

X=0.5

X=0.52

X=0.83

X=0.92

X=1.00

T = 2 K

Energy (meV)

0 10 20 30 40

Imaginary part of susceptibility (

)

Magnetic response at Q
AF

slice in Q space

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Observation of resonance peak


YBCO
6.85

J. Rossat
-
Mignod et al., 1991

Energy (meV)

Intensity

Q
AF

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Extraction of magnetic response

Where is the interesting range
in Q and energy?

Broad dynamical range

YBCO
6.6

P. Dai et al., 1999

Q
AF

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YBCO
6.85

L.P. Regnault et al., 2002

Energy (meV)


Q = Q
-

Q
AF

in reciprocal lattice units

Q
AF

resonance

FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Polarisation analysis

Unusual dispersion

Close look at resonance

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Obtaining more data is required

Broad range in frequency

from 1 neV to 100 meV




and Q space

Coupling to all degrees of freedom

polarisation analysis

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Phonon dispersion in YBa
2

Cu
3

O
7
-
x


Egami et al., (2002)

Phonon energy (meV)

Q in reciprocal lattice units

Neutrons will be needed

to unravel the relevant couplings

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW

Many examples in other fields

Mapping a wide time and space domain

Quantum spin chains

M. Enderle et al., 2001

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FLUCTUATIONS IN SOLIDS :




THE GLOBAL VIEW



ESS offers unprecedented capabilities :



flux



coverage of (t,r) space



neutron polarisation analysis



ESS will allow to reach new scientific

frontiers

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BCS superconductivity

MgB
2

T
c

~ 39 K

Isotopic effects

Temperature (K)

Magnetisation

Mg
10
B
2

Mg
11
B
2

S.L. Bud’ko et al., 2001

Marginal shift with Mg isotope change

Mg

B

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Ch. Dewhurst ,B. Cubitt, 2002

Temperature (K)

Conventional BCS

No node in the gap

(Intensity)
1/2

Vortex Lattice in MgB
2

Isotropic penetration depth

BCS superconductivity