Dynamical behavior of Josephson vortices

1
"Symposium on Neural Networks and Cellular
Automata from superconducting junctions to
biology"., 4-5 Feb. 2008, Loghborough
University, UK
Dynamical behavior of Josephson vortices in
Bi2Sr2CaCu2O8dpossibility of using for neural
network Kazuto HIRATA National Institute for
Materials Science, Tsukuba, Japan
Collaborators
Feodor V. Kusmartsev Sergey Savelev Dmitry R.
Gulevich
Shuuichi Ooi Takashi Mochiku
Franco Nori
Marat Gaifullin
2
OUTLINE

• Experiments on Jpsephson-vortex motion.
• -----
  moving in high velocity
• Josephson vortices in intrinsic Josephson
  junctions (IJJs) of HTSCs (Bi-2212) vortex
  motion for neural network (fluxtronics)
• ----- ratchet effect, vortex cloning,
  MQT,
• 
  vortex tunneling.
• Simple device with IJJs
• Rectification effect of Josephson vortices.
• Summary.

3
synapse
Neural network in brain
dendrite
synapse
soma
axon
Model-II
Model-I
4
Josephson vortices in high Tc superconductors
Observation with scanning SQUID Kirtley, et
al.,PRL81(1998)2140.
large g (lc/lab)
strong anisotropy
g s
.... without normal core
Josephson vortex
... Dilute Case
5
Soliton in Josephson- transport line
A. Masuda T. KawakamiPRL51(1983)694. H. Akoh,
S. Sakai, A. Yagi H. Hayakawa, IEEE Trans.
Magn. 21(1985)737. A. Fujimaki, K. Nakajima Y.
Sawada, J. Appl. Phys. 61(1987)5471.
A. Fujimaki, K. Nakajima Y. Sawada, PRL
59(1987)2895.
Schematic block diagram of the circuit
After collision, decaying with breather mode
Schematic drawing of the sample
6
Crystal structure of Bi2Sr2CaCu2O8d(Bi-2212)
Supercon-ducting layer
Non-super-conducting layer
1.5nm
Josephson vortices
H//ab
Supercon-ducting layer
7
Periodic Oscillations in JV Flow Resistance
(PRL89(2002)247002)
Focused Ion Beam fabrication into a
micron-size Junction
Hp DH0/2
Increment of the field
Hp 406 Oe
DH0 f0/ws 784Oe
Bi-2212 Single Crystal
Typical size 17.6x14.0x1.60mm3
8
Assuming the triangular Josephson Vortex Lattice
Bottom of the oscillations
To clarify the dynamical behaviors of Josephson
vortices, numerical calculations were made by
Machida (PRL90(2003)037001),
Koshelev(PRB66(2002)224514).
9
Flow resistance of JV (smaller width)
DH0 f0/ws
2594 Oe
2Hp 2864 Oe 2Hp gt DH0
Existence of the effective width wew2lj (lj
Josephson penetration depth. 0.25 mm)
DH0 f0/ws
2863 Oe
Extrapolating the bottom position, it coincides
to the origin
Measurement of Absolute Value of magnetic field
Hb n x Hp
10
Measurement of magnetic field from flow
resistance of JV
Supercond. Sci. Technol., 17(2004)S432.
The largest slope 1.2974 ohm/Oe at 25.1 kOe
The current along the c-axis 0.1 mA
The flow voltage 0.12974 mV/Oe
The resolution of voltage measurement is less
than pV range mOe range is possible to measure.
Precise measurement of magnetic field
11
Control of vortex motion for the next generation
devices
Vortex pumping effect Lens Wambaough, et
al PRL 83(1999)5106
theoretical proposal
(by Franco Nori, RIKEN)
vortex pumping Grigorenko, et al Nature
414(2001)728.
Cole, et al Nat. Mater., 5(2006)305
experiments
12
Control of vortex motion for the next generation
devices
experiments
J.E. Villegas, et al, Science 302(2003)1188. J.
van de Vondel, et al, PRL 94(2005)057003 Silva,
et al Nature 440(2006)651
theoretical proposal
Reversible diodes for moving quanta S. Savelev,
F. Nori Nature Matter. 1(2003)179, F. Nori
Nature Physics. 2(2006)227
13
Controlled multiple reversals of a ratchet
effect Silva, et al Nature 440(2006)651
Positive and negativeVdc
Silva, et al Nature 440(2006)651.
Rachet effect for an a.c. bias
Schematic drawing of the sample
AFM image
1.5 mm
Symmetric in vortex motion Vdc0
H-T dynamical phase diagram
14
Ratchet without spatial asymmetry for controlling
the motion of magnetic flux quanta using
time-asymmetric drives
Cole, et al Nature Materials 5(2006)305.
15
Rectification in spatially-asymmetric rachets (by
Franco Nori, RIKEN)
InputOutput signals
V-I
Vortex motion
Single harmonic
two harmonics
16
D.R. Gulevich F.V. Kusmartsev PRL97(2006)017004
VORTEX CLONING
Stored energy in Additional JTL
Critical velocity on the ratioo of width W/W0
Critical driving current g j/jc
gc vs W/W0
17
Josephson Vortex-Antivortex Bound State
D.R. Gulevich F.V. Kusmartsev(preprint)
Critical initial velocity for trapping the pair
Evolution of the energy of a fluxon-antifluxon
pair
Trapped fluxon-antifluxon pair forms a breather.
fluxon-antifluxon pair annihilation may
cause microwave emmision.
18
Macroscopic Quantum tunnelling through IJJ
(Inomata, et al PRL 95 (2005) 107005.)
c-axis currrent for controlling the motion of
vortices
Macroscopic Quantum Tunneling
Quantum Tunneling of Single Flux
19
Tilting the magnetic field H? to H//
Koshelev, et al PRL 83(1999)187.
Grigorenko, et al Nature 414(2001)728.
20
Rectification of Josephson-vortex motion
S. Ooi, et al., PRL99(2007)207003
SIM image of the sample
Junction size 14.8x24.5x0.6mm3
Lorentz force
10mm
21
Pancake vortices in liquid state
pancake vortices
Bi-2212
Josephson vortices
(17/22)
22
Pancake vortices in glass(pinned) state
pancake vortices
Bi-2212
Josephson vortices
(18/22)
23
Simulations for the dynamics of JVs with PVs
by Sergey Savelev
Differential equations
pancake vortices
Bi-2212
Josephson vortices
(19/22)
24
Rectification in spatially-asymmetric ratchets
InputOutput signals
V-I
Vortex motion
Single harmonic
two harmonics
25
Rectification of Josephson-vortex motion
S. Ooi, et al., PRL99(2007)207003
Enhancement ofV with PV
Dc current 100mA
Rectified dc voltage Vdc(n1,n2) normalized by
V Vdc(n1,n22n1) (n2100Hz, I01mA, 10K)
Rectified dc voltage VVdc(n1,n2,j0)) (n22n120
0Hz, I01mA, 10K)
The measured peaks are perfectly reproduced
Simulated rectified dc voltage Vdc(n1,n2,j0)
26

• Summary
• Introduction on Experiments on Jpsephson-vortex
  motion.
• Josephson vortices in intrinsic Josephson
  junctions (IJJs) of HTSCs (Bi-2212) vortex
  motion for neural network (fluxtronics)
• ----- ratchet effect, vortex cloning, MQT,
  vortex tunneling.
• Simple device with IJJs
• Rectification of Josephson-vortex motion with
  pancake vortices.

27
Rectification of pancake-vortex motion in
Bi-2212 anti-dots array
S.Ooi, et al PRL99(2007)207004
Voltage-current characteristics with -5Oe at H2
Dia. 300nm 1mm space
Matching field H1 25Oe
Tc 87.8K(R0)
Idrive(n1, n2, j) I0cos(n1t)cos(n2tj)
Rectified dc voltage V/V (VVdc(H1, j0))
(n22n120Hz, I010mA,86.8K)
H2
DC voltage can be controlled by changing j from
positive to negative value continuously.
H1
28
Previous Experiments on JV Flow-Resistance
Ooi, et al PRL89(2002)247002
Flow-resistance shows periodic oscillations upto
close to Tc and in high magnetic fields
SIM-Image
Bi-2212
Schematic drawing of the sample
29
Magnetic Phase Diagram of JV in Bi-2212
Hirata, et al Physica C 437-438(2006)100-103
The upper boundary of 3D-ordered state Hu and
the lower boundary Hl show a shift to higher
magnetic field with doping
Hu
Sample A
Sample B
Good tendency towards weakly anisotropic HTSC
3D-Long Range Ordering
Corresponding to the melting line
No explicit experimental evidence of the first
order transition
Magnetic Field kOe
Triangular Lattice Phase
Hl
Sample TC Hl g A
78.2 K 8.4 kOe 170 B 82.0 K 6.2 kOe
240
Reduced Temperature T/Tc