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Vortex Dynamics in Vortex Dynamics in Type II Type II
SuperconductorsSuperconductors
Yuri V. ArtemovYuri V. ArtemovPh.D. Student in Physics
Mentor:
Brian B. SchwartzBrian B. SchwartzProfessor of Physics
CUNY Fall 1998
OverviewOverview
• Properties of superconductors
• Two types of superconductors
• Theories of superconductivity
• Vortices in type II superconductors
• Interaction between vortices
• Interaction with defects• Vortex dynamics• Proposed research• Vortices and computers• Summary
Perfect conductor
yrs10dtdI
I
0ρ
5
Properties of Properties of SuperconductorsSuperconductors
Meissner effect
cTT
0B
cTT Magnetic fielddestroys s/c
cHH cHH
0
Ic Bc
Electric currentdestroys s/c
Two Types of Two Types of SuperconductorsSuperconductors
Magnetization
Magnetic Field
Critical Field
-4M
HHc
-4M
HHc1 Hc2
H
B
Hc1 Hc2
H
B
Hc
Type IIType I
T
Hc
Tc
Superconductor
Normal Metal
T
Hc
Tc
Superconductor
Normal Metal
Mixed State
Theories of Theories of SuperconductivitySuperconductivity
• London Equation
field magneticofenergy
2
currentpermanent ofenergy kinetic
s2
0 rd8π
Hrdnmv
2
1FF
0HH0F 2
H λx
eH
• BCS Theory
• Ginzburg-Landau Theory
2/1c MT
•Electrons can attract via phonons
•Attraction leads to energy gap 1.76Tc
isotope effect
EF EF
2Normal Metal Superconductor
Amc
e4
m
eiB
4
cj
0Ac
e2
im2
1
T4H,
T
T
TTT
8
HA
c
e2i
m2
1
2FF
22
**s
2
2/12
c
2
c
c0
2242
n
II type21
I type21
parameter GL
Te24
mcT
Tm2T
2/1
2
2
2/12
H
r
Vortices in Type II Vortices in Type II SuperconductorsSuperconductors
quantumflux e2
hc,rzHH 020
2
rK
2H 02
0
r,er22
H
r,r
ln2
H
/r2
0
20
Magnetic Field
j
r
Current
r
Order Parameter
Interaction between Interaction between VorticesVortices
B
J
FL
Lorenz type force
Jc
F 0L
BB
FLJ
Repulsion
ss0
L vnh2
1J
cF
Triangular lattice
2102
012
12012
112221
2
12
212121
2
21
221202
rrK
2H,
4
HU
dHHdHH8
U
ddHHHH8
F
rHrHrH
rrrrzHH
Interaction with Interaction with DefectsDefects
B
J
FL
Jc
F 0L
Flux Creep
Activation energy behavior
Pinning
• Vacancies, voids, inhomogeneities, where superconductivity is weak
• Pinning decreases energy losses caused by flux creep
Vortex DynamicsVortex Dynamics
• Collective behavior– Vortices interact strongly
• Effects of disorder– Interaction with pinning centers
• Many degrees of freedom– 1012 vortices in a sample
• Threshold dynamics– Can be driven to marginally
stable state
Proposed ResearchProposed Research
Study the dynamics of vortices in type II superconductors
Given a superconductor with a certain pinning landscape, how do vortices move inside it?
How do microscopic pinning parameters affect measured macroscopic quantities?
How do vortices start moving when slowly driven towards the threshold of instability?
How to characterize dynamical instabilities in a superconductor?
Vortices and Vortices and ComputersComputers
Vortices can be studied using computer simulations– A powerful theoretical tool to
answer questions raised above– Allows to study phenomena hard to
observe experimentally Vortices can be effectively
visualized using modern 3D design software– Making them more understandable
to non-physics audience Tools to be used
– Powerful workstations at the CUNY New Media Lab
– Softimage 3D software– DirectX technology with Visual C++
and Visual Basic– Matlab, Mathematica– Java & WWW
SummarySummary
General properties of superconductors
Type I and type II superconductors
Theories of superconductivity
Vortices in type II superconductors
Vortex interactions and dynamics
Proposed research Using computers to
study and visualize vortices