Transcript 101 Years of Superconductivity - fz

PAUL SCHERRER INSTITUT
101 years of superconductivity
Kazimierz Conder
Laboratory for Developments and
Methods, Paul Scherrer Institute,
5232 Villigen PSI, Switzerland
[email protected]
Resistivity
Electrical resistivity at low temperatures
Kelvin: Electrons will be frozen
– resistivity grows till .
Kelvin (1902)
Matthiessen (1864)
Dewar (1904)
Temperature
Dewar: the lattice will be
frozen – the electrons will not
be scattered. Resistivity wiil
decrese till 0.
Matthiesen: Residual resistivity
because of contamination and
lattice defects.
One of the scientific challenge at the end of 19th
and beginning of the 20th century: How to reach
temperatures close to 0 K?
Hydrogen was liquefied (boiling point 20.28 K)
for the first time by James Dewar in 1898
2
Superconductivity- discovery I
1895 William Ramsay in England
discovered helium on the earth
1908 H. Kamerlingh Onnes liquefied
helium (boiling point 4.22 K)
Resistivity at low temperatures- pure
mercury (could repeatedly distilled
producing very pure samples).
•Repeated resistivity measurements indicated zero resistance at the liquid-helium
temperatures. Short circuit was assumed!
•During one repetitive experimental run, a young technician fall asleep. The helium
pressure (kept below atmospheric one) slowly rose and, therefore, the boiling
temperature. As it passed above 4.2 K, suddenly resistance appeared.
Hg TC=4.2K
From: Rudolf de Bruyn Ouboter, “Heike Kamerlingh Onnes’s
Discovery of Superconductivity”, Scientific American March 1997
Superconductivity- discovery II
•Liquid Helium (4K)
(1908). Boiling point
4.22K.
•Superconductivity in
Hg TC=4.2K (1911)
„Mercury has passed into a new state,
which on account of its extraordinary
electrical properties may be called the
superconducting state“
H. Kamerlingh Onnes 1913 (Nobel preis 1913)
Resistivity R=0 below TC;
(R<10-23 cm, 1018 times
smaller than for Cu)
4
Further discoveries
1911-1986: “Low temperature
superconductors” Highest TC=23K
for Nb3Ge
1986 (January): High Temperature
Superconductivity (LaBa)2 CuO4
TC=35K
K.A. Müller und G. Bednorz (IBM
Rüschlikon) (Nobel preis 1987)
1987 (January): YBa2Cu3O7-x TC=93K
1987 (December): Bi-Sr-Ca-Cu-O TC=110K,
1988 (January): Tl-Ba-Ca-Cu-O TC=125K
1993: Hg-Ba-Ca-Cu-O TC=133K
(A. Schilling, H. Ott, ETH Zürich)
5
140
HgBa2Ca2Cu3O8
Tl2Sr2Ca2Cu3O10
120
Bi2Sr2Ca2Cu3O10
TC [K]
100
YBa2Cu3O7
Liquid nitrogen
80
60
La2-xSrxCuO4
40
NbN
20
Hg
Pb
Nb
Nb3Sn
Nb3Ge
NaxWO3
NbO
MgB2
Cs2RbC60
Ba1-xKxBiO3
BaPb1-xBixO3
LHe
0
1920
1940
1960
Year
1980
2000
6
Zero resistivity
Low temperatures:
LN2 -1960C (77K)
The current can flow 100 000
years!!
7
Meissner-Ochsenfeld-effect
A superconductor is a perfect
diamagnet. Superconducting
material expels magnetic flux from
the interior.
W. Meissner, R. Ochsenfeld (1933)
On the surface of a superconductor
(T<TC) superconducting current will
be induced. This creates a magnetic
field compensating the outside one.
Screening (shielding ) currents
Magnetic levitation
8
Superconducting elements
•Ferromagnetic elements are not superconducting
•The best conductors (Ag, Cu, Au..) are not superconducting
•Nb has the highest TC = 9.2K from all the elements
9
Classical model of superconductivity
1957 John Bardeen, Leon Cooper, and John Robert Schrieffer
An electron on the way through the lattice interacts with lattice
sites (cations). The electron produces phonon.
During one phonon
oscillation an electron can
cover a distance of ~104Å.
The second electron will
be attracted without
experiencing the repulsing
electrostatic force .
The lattice
deformation
creates a region
of relative
positive charge
which can attract
another electron.
10
Nobel Prize in Physics
1972
"for their jointly developed
theory of superconductivity,
called the BCS-theory”
John Bardeen, Leon Neil Cooper, John Robert Schrieffer
eCoherence
length 
Phonon
Cooper pair model
e-
Fermie und Bose-Statistic
Energy
Energy
Density of states
•Fermions- elemental particles
with 1/2 spin (e.g. electrons,
protons, neutrons..)
•Pauli-Principle –every energy
level can be occupied with
maximum two electrons with
opposite spins.
Density of states
Cooper-Pairs are created with
electrons with opposite spins.
•Total spin of C-P is zero. C-P are
bosons. Pauli-Principle doesn’t
obey.
•All C-P can have the same
quantum state with the same
energy.
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Creation of a C-Pairs diminishes
energy of electrons. Breaking a
pair (e.g. through interaction
with impurity site) means
increase of the energy.
A movement of the C-P when a
supercurrent is flowing, is
considered as a movement of a
centre of the mass of two
electrons creating C-P.
eAll the C-P are in the same quantum
state with the same energy. A
scattering by a lattice imperfection
(impurity) can not change quantum
state of all C-P at the same time
(collektive behaviour).
Phonon
e-
BCS Theory: some consequences
Good electrical conductors
are showing no
superconductivity
In case of good conductors is the
interaction of carriers with the
lattice very week. This is, however,
important for superconductivity.
Isotope effect
The Cooper-Pairs are created
(“glued”) by the electron-phonon
interaction. Energy of the phonons
(lattice vibrations) depends on the
mass of the lattice site .
Superconductivity (Tc) should
depend on the mass of the ions
(atoms) creating the lattice.
TC~M-
For most of the lowtemperature
superconductors =0.5
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What destroys superconductivity?
A current: produces magnetic field which in turn
destroys superconductivity.
Current density
Temperature
Magnetic field
Magnetic field: the spins of the C-P
will be directed parallel.
High temperatures:
strong thermal vibration
of the lattice predominate
over the electron-phonon
coupling.
(should be antiparallel in C-P)
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Coherence length 
Concentration C-P
Superconductor
SL
SC
(Xi)
I
SC
SL
x< GL
Coherence length is the
largest insulating distance
which can be tunneled by
Cooper-Pairs.
GL
Coherence length is the distance
between the carriers creating a
Cooper-Pair.
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Nobel Prize in Physics 1973
"for his theoretical predictions of the properties of a
supercurrent through a tunnel barrier, in particular
those phenomena which are generally known as the
Josephson effects".
Brian David Josephson
The superconducting tunnel Josephson)
junction (superconductor–insulator–
superconductor tunnel junction (SIS) —
is an electronic device consisting of two
superconductors separated by a very thin
layer of insulating material
Josephson discovered in
1963 tunnelling effect being
23-years old PhD student
SL
SC
I
x<
SL
SC
GL
Superconductor
Eindringtiefe

depth
Penetration
Penetration depth
(T)=0*(1-(T/TC) )
4 -0.5
0
 depicts the distance where
B(x) is e-time smaller than on the
surface
TC
Temperatur
Temperature
18
Ginzburg-Landau Parameter =/GL
<1/2=0.71 Superconductor Type I
Al
Sn
Pb
Tc
 [nm] [nm]

1.2
3.7
7.2
16
34
37
0.01
0.16
0.4
1600
230
83
>0.71 Superconductor Type II
Nb
Nb3Sn
YBa2Cu3O7
Rb3C60
Bi2Sr2Ca2Cu3O10
Tc
 [nm] [nm]

9.3
18
93
30
110
39
80
150
247
200
1
27
100
124
143
19
38
3
1.5
2.0
1.4
Superconductor type I (/GL<0.71) in a magnetic field
Bi=Ba+0M
Outside field
Inside field Bi
Magnetization –μ0M
The field inside the
superconductor
Outside field Ba
Superconductor
Bi=0
The field created on the
surface of the superconductor
compensating the outside field
Negative units !
Outside field Ba
Normal
conductor Bi=Ba
20
Superconductor type II in a magnetic field
Meissner
phase
Mixed
phase
Outside field Ba
Normal
conductor
Average inside field Bi
Magnetization –μ0M
Bi=Ba+0M
Outside field Ba
Vortex-lattice in
superconductor type II.
Magnetic flux of a vortex is
quantized:
0=h/2e2.07·10-15Tm2
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Magnetic induction B
Superconductor type II. B-T-Diagram
Normal state
Mixed phase
Meissner
phase
Temperature T
STM (Scanning Tunneling
Microscopy). Abrikosov-lattice
in NbSe2
H. Hess, R.B. Robinson, and J.V. Waszczak,
Physica B 169 (1991) 422
22
Nobel Prize in Physics
2003
"for pioneering
contributions to the theory
of superconductors and
superfluids".
Alexei A. Abrikosov, Vitaly L. Ginzburg, Anthony J. Leggett
Type I
Type II
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Perovskite ABX3
X
B
A
X=O2-, F-, Cl-)
A=alkali, alkali-earth and rareearth metals,
B=transition metals (also Si, Al,
Ge, Ga, Bi, Pb…)
Perovskite is named for a Russian
mineralogist, Count Lev Aleksevich
von Perovski. The mineral (CaTiO3)
was discovered and named by Gustav
Rose in 1839 from samples found in
the Ural Mountains.
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High Temperature Superconductor. La2-xSrxCuO4
(LaBa)2 CuO4 TC=35K K.A. Müller und G.
Bednorz (IBM Rüschlikon 1986 )
Cu
TC
Metal
TN
Insulator
100
Antiferromagnet
La, Sr
Temperature [K]
O
La2-xSrxCuO4
Superconductor
10
0.0
0.1
0.2
0.3
Sr-content x, (holes per CuO2-layer)
2SrO  2Sr‘La + 2OxO + VO
VO+ 0.5O2 OxO+ 2h
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High Temperature Superconductor: YBa2Cu3O7-x
BaO
CuO2 –layer
Y
5-fold Cu
coordination
CuO-chain
4-fold Cu
coordination
Perovskite
“YBa2Cu3O9”
27
Oxygen doping in YBa2Cu3O7-x
TC
YBa2Cu3O7-
80
60
40
Superconductor
20
6.2
6.4
6.6
6.8
Oxygen content (7-)
Oxygen content depends
on temperature and
oxygen partial pressure
7.0
Thermogavimetry
7.0
100.0
YBa2Cu3O6.985
6.8
99.5
6.6
99.0
98.5
200
400
600
800
6.4
1000
o
Temperature [ C]
28
Oxygen index
0
6.0
Weight [%]
Temperature [K]
100
Layered structure of YBa2Cu3O7-x
CuO
BaO
CuO2
Y
Conducting CuO2 layers
Charge reservoir
Conducting CuO2 layers
holes
electrons
holes
2Cu2+ + 0.5O2  2Cu3+ +O22CuxCu + V O +0.5O2  2CuCu + OxO
2CuCu  2CuxCu + 2h
29
Layered structure of YBa2Cu3O7-x. Anisotropy
Unit cell
Cooper-pairs can not tunnel through
the charge reservoir!
3.4Å
YBa2Cu3O7
ab [Å]
8.3Å
1500
c [Å]
6000
TC=93
ab [Å]
c [Å]
15
4
Bi2Sr2Ca2 Cu3O10 TC=110
ab [Å]
2000
c [Å]
10 000
ab [Å]
c [Å]
13
2
For YBa2Cu3O7 single crystals at 4.2K
jc(ab)~107A/cm2, jc(c)~105A/cm2
30
Bi-Sr-Ca-Cu-O
Ca
Ca
BiO
BiO
SrO
CuO2
Ca
Ca
Ca
Ca
Ca
Bi2Sr2CuO6 2201
TC=20K
Bi2Sr2CaCu2O8 2212
TC=95K
Bi2Sr2Ca2Cu3O10 2223
TC=110K
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HgBa2Can-1CunO2n+2 “Hg-12(n-1)n”
CuO2-layers
World record 133K !!!
ETH Zürich - A.Schilling, M.Cantoni, J.D.
Guo, H.R.Ott, Nature, 362(1993)226
TC für HgBa2Can-1CunO2n+2
Hg-12(n-1)n
Temperature [K]
140
130
120
110
100
90
1
2
3
4
5
6
7
Number of CuO2-layers in the unit
32 cell
Magnetic ion in the structure
Sm
TC=55K
April, 2008
33
Cs0.8(FeSe0.98)2
FeSe
Intercalation
K0.8(FeSe0.98)2
Cs0.8(FeSe0.98)2
Cs
Crystal growth in Cs (or K)- vapour in
quartz ampoules at 1050oC
New superconductor Lix(C5H5N)yFe2-zSe2
Synthesized via intercalation of dissolved alkaline metal (Li)
in anhydrous pyridine at room temperature.
C 5H5N
Synthesis of a new alkali metal-organic solvent intercalated
iron selenide superconductor with Tc≈45K
A. Krzton-Maziopa, E. V. Pomjakushina, V. Yu. Pomjakushin, F.
von Rohr, A. Schilling, K. Conder
arXiv:1206.7022
USO
USO
Unidentified Superconducting Object
36
Applications. Wires and bands.
Abfüllen in
Silberröhrchen
und Schweissen
Extrusion
Extrusion
c ab
Walzen und Erhitzen bei
800-900oC
37
American Superconductor
Applications. Wires and bands.
Cross section of HTC
band
American Superconductor
Corporation
HTC Cable
38
Application. Industry.
Magnetic bearing
A flywheel in a vacuum chamber – energy
accumulator.
MagLev – train
(magnetic levitation)
SMES: Superconducting
Magnetic Energy
Storage
Saves energy in form of
magnetic field produced
by a superconducting
coil.
39
Summary
•History of discovery and farther development
•How it works (still open problem for HTc)
•What are the materials
•Potential applications
A spin of a Cooper pair is:
1
1/2
2
0
Most of the HTc superconductors are:
Cuprates
Nickelates
Cobaltates
Manganates
Superconductors type II in comparison to type I:
have shorter coherence length
and longer penetration depth
have shorter coherence length
and shorter penetration depth
are cuprates (all other
superconductors are type I)
have longer coherence length
and shorter penetration depth
In the BCS theory it is assumed that the interaction between electrons in Cooper pairs is
mediated by:
photons
Coulomb force
phonons
magnetic interaction
Vortex phase is observed:
For all superconductors type I
Only in cuprates
For all superconductors above
Tc
For all superconductors type II
Isotope effect (Tc dependence on lattice mass) is:
a proof of BCS theory
(electron-phonon interaction)
a proof that superconductor is
of type II
only observed for hole doped
superconductors
not observed in
superconductors
In case of many High Temperature superconductors in order to achieve temperatures
below Tc one can use:
Ice+water
Liquid nitrogen
Dry ice (solid CO2sublimation at −78.5 C)
No cooling is necessary