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Quasi One-Dimensional Vortex Flow Driven Through Mesoscopic Channels

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.

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Quasi One-Dimensional Vortex Flow Driven Through Mesoscopic Channels

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  1. 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

  2. E J Driving force for vortices E Electric field due to vortex motion velocity Jｃ hv = F J Driving force Dissipations in normal core(~px2) Vortex flow Pinning force for vortices Fp = Jc B H Baarle et al APL 2003

  3. b BS Formula for 1D chain 1D Bardeen Stephen(BS) Formula Vortex density B: BS Formula for flux flow resistivity b a l Flow

  4. 1D Vortex Flow in Twin Boundaries A. Gurevich PRL, PRB 2002 b a Abrikosov Josephson vortex

  5. IV Curves in Twin Boundaries

  6. 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

  7. Mesoscopic Vortex Flow Channels 0.2 – 1mm Strong pinning NbN layer J H Weak pinning a-NbGe layer J w < l SEM picture (w=650nm)

  8. 2.0 w=230 nm ) ~c (B) 3 66 N/m 1.0 6 (10 p F experimental data 0 a 0 0.4 1.2 0.8 Matching condition m0H (T) Mismatch condition b Matching Effects The shear modulus of vortex lattice c66 w f J

  9. v a Simplified picture I= Idc + Irfsin(2pft ) Velocity fint = p f vML ML occurs : (vML = p a f) Force Mode Locking Experiments : Model • Coherent flow, average velocity ‘v’ in pinning potential fint = v/a Lattice Mode : Flow direction a: particle spacing // v

  10. p=3 Large Irf p=2 Irf=0 p=1 weff f=6MHz a b Mode Locking Experiments: Result w=230nm T<<Tc(NbGe)

  11. Field Evolution of n and Fc Vortex density Oscillation in Fc is closely related with the flow configurations in channels PRL 88,247004 (2002)

  12. Quasi 1D flow properties NbN A decoration image in channels in a field of 50mT taken by N. Saha, Field History in Channels NbN Field down (FD) mode H is ramped down after applying a large field (>Hc2 of NbGe) • Field up (FU) mode • H is ramped up after ZFC • Field Focusing in channels Conventional 2D FF behavior

  13. H* Field History of Ic & IV Curves

  14. Low I Flow Resistance High I a = 0.5 H < H* 1D like vortex flow

  15. n = 5 n = 3 f (MHz) (= v/a) Dynamic Change in Flow Structure f = fint = v/aat p=1 DC A kink anomaly mark a dynamic change in flow configuration

  16. H < H* constant n Quasi 1D flow properties H > H* H* Conventional (2D) Flux Flow H* Quasi 1D flow Properties n = 5 High RFB n = 4 Low RFB Lower R.F. branch : n Higher R.F. branch: n+2 H* : 1D - 2D flow transition

  17. FD FU Mobile Mobile Field profile in a channel

  18. 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

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