quasi one-dimensional vortex flow driven through mesoscopic channels
DESCRIPTION
Quasi One-Dimensional Vortex Flow Driven Through Mesoscopic Channels. Nobuhito Kokubo. Institute of Materials Science, University of Tsukuba. R. Besseling, T. Sorop, P. H. Kes Kamerlingh Onnes Laboratory, Leiden University. E. J. Driving force for vortices. E. - PowerPoint PPT PresentationTRANSCRIPT
Quasi One-Dimensional Vortex Flow Driven Through Mesoscopic Channels
R. Besseling, T. Sorop,
P. H. KesKamerlingh Onnes Laboratory, Leiden University
Nobuhito Kokubo
Institute of Materials Science, University of Tsukuba
Pinning force for vortices
Fp = Jc B
J cJ
E
Driving force
velo
cit
y
Electric field due to vortex motion
vBE
E
Vortex flow
Baarle et al APL 2003
BJF
Driving force for vorticesJ
H
Dissipations in normal core
v = F
BS Formula for 1D chain
BaldB
ldbRc
nfDf
1
2
01
l
1D Bardeen Stephen(BS) Formula
BabB
B
cn
f
1
2
0
0
Vortex density B:
Bab 0
BS Formula for flux flow resistivity
a
b
b
Flow
1D Vortex Flow in Twin Boundaries
A. Gurevich PRL, PRB 2002
a
HR f
b
Abrikosov Josephson vortex
IV Curves in Twin Boundaries
Outline of This Talk
Vortex flow channel device
A short summary of previous results
New results•A kink anomaly in IV characteristics•ML experiments
Summary of this talk
J
JH
Weak pinning a-NbGe layer
Strong pinning NbN layer
Mesoscopic Vortex Flow Channels
SEM picture (w=650nm)
0.2 – 1m
w <
Matching Effects
w=230 nm
0 0.4 0.8 1.20
1.0
2.0
~c66(B)
F p (
106 N
/m3 )
0H (T)
experimentaldata
/w 66cFp
J
w
The shear modulus of vortex lattice c66
f
Mismatch conditionMatching condition
b
a
Mode Locking Experiments : Model
Coherent flow, average velocity ‘v’ in pinning potential
a: particle spacing // vv
aSimplified picture
Force
vMLVe
loc
ity
Lattice Mode : fint = v/a
I= Idc + Irf sin(2ft )
ML occurs : fint = p f(vML = p a f)
Flow direction
Mode Locking Experiments: Result
BvE
avff /int
abB /0
weff
b
a
b
wn eff
fnV pc 01
f=6MHz
Irf=0
Large Irf
p=1
p=2
p=3
T<<Tc(NbGe)
w=230nm
PRL 88,247004 (2002)
Vortex density
Oscillation in Fc is closely related with the flow configurations in channels
Field Evolution of n and Fc
Field History in Channels
Field up (FU) modeH is ramped up after ZFC• Field Focusing in channels
A decoration image in channels in a field of 50mT taken by N. Saha,
NbN
Quasi 1D flow properties
Field down (FD) modeH is ramped down after applying a large field (>Hc2 of NbGe)
Conventional 2D FF behavior
NbN
Field History of Ic & IV Curves
H*
Flow Resistance
HRd
H < H* 1D like vortex flow
Low I
High I
f (MHz) (= v/a)
A kink anomaly mark a dynamic change in flow configuration
DC
n = 3
n = 5
Dynamic Change in Flow Structure
f = fint = v/a at p=1
H*
Lower R.F. branch : n Higher R.F. branch: n+2
Quasi 1D flow Properties
constant n
HRd H < H*
Quasi 1D flow propertiesn = 4
n = 5 High RFB
Low RFB
H*
H > H*
Conventional (2D) Flux Flow
HRd
H* : 1D - 2D flow transition
Field profile in a channel
FD
Mobile
FU
Mobile
Summary
• Mesoscopic channel system provides very rich physical properties
• Field history changes the vortex dynamics in channels
• Quasi-1D motion (square root dependence on field with constant flow configurations)
• Dynamic change in flow configurations
• Transition from quasi1D to 2D flow properties