1. Experiments with semifluxon generator Edward Goldobin University of Tübingen, Germany M. Paramonov, M. Fominsky, V. Koshelets IRE RAS, Moscow [Logo of МОН 1.5 here]

2. Where is Tübingen? Tübingen Tübingen: small university town on r. Neckar population ~80000 30 km south from Stuttgart -- a capital of Baden-Württemberg University: students ~28000 university is 530 years old !!! two faculties of theology ;-) strong medicine phys., chem., math are small Our Group (~30 people): 2 Profs: R. Kleiner, D. Koelle 1 Assistant Prof. 4 Post Docs ~12 PhD students ~10 Diploma students

3. Josephson junction Conventional JJ. ( 0 -junction) Unconventional JJ (  -junction) SISSIS SISSIS I I +other terms j c =1–5000 A/cm 2, (Nb-AlO x -Nb)

4. Long Josephson 0-  junction 0  x 1D model

5. YBCO-Nb ramp zigzags  H.-J. Smilde at al. PRL 88, 57004 (2002) LTSEM image of supercurrent E. Goldobin, R. Straub, D. Dönitz, D. Koelle, R. Kleiner, H. Hilgenkamp (2003).

6. SFS/SIFS junctions  V. Ryazanov et al. PRL 86, 2427 (2001)  T. Kontos et al. PRL 89, 137007 (2002)

7. sine-Gordon equation for 0-  LJJ Phase discontinuity points!  Goldobin et al., PRB 66, 100508 (2002) — dimensionless damping — the first critical field — dimensionless field

8. Semifluxon=vortex carrying    Pinned, two degenerate states  and   Goldobin et al., PRB 66, 100508 (2002)  Xu et al., PRB 51, 11958 (1995)

9. Mechanical analog:pendula chain (x)(x) (x)(x)

10. Semifluxons observation SQUID microscopy on YBCO-Nb ramp zigzag LJJs  H. Hilgenkamp et al. Nature 422, 50 (2003).

11. Artificial 0-  junctions  Goldobin et al., Phys. Rev. Lett. 92, 057005 (2002) A. Ustinov, Appl. Phys. Lett. 80, 3153 (2000).

12. Nb LJJ with two injectors J  30  m (j c  100 A/cm 2 )

13. Calibration of injectors NumericalExperimental Goldobin et al., PRL 92, 057005 (2004)

14. Switching on the current...  at zero bias we have a static pinned semifluxon.  bias current pulls semifluxons, just like fluxons.  but semifluxons are pinned --> deformation  at bias=  I c  0.64 I c switching to the R-state  Goldobin et al., PRB 67, 224515 (2003).

15. I c (H) of long 0-  JJ  N. Lazarides, PRB 69, 212501 (2004).

16. magnetic field Overcritical bias:oscillator èFrequency depends on: èbias current, damping, length ètwo outputs shifted by 180° èmore stable than flux-flow due to semifluxon pinning voltage  N. Lazarides, PRB 69, 212501 (2004).

17. Semifluxon -- half-integer ZFS  Finite length --> image technique:  1 real semifluxon + 2 anti-semifluxons (images)  Bias current  Force  SF hopping. Goldobin et al., Phys. Rev. B 67, 224515 (2003).

18. Half integer ZFS (full IVC) Goldobin et al., PRL 92, 057005 (2004)

19. Half integer ZFS Goldobin et al., PRL 92, 057005 (2004)

20. Experiments last week in IRE

21. Layout L = 16..32  m dx=dw=1, 1.5, 2  m

22. Calibration: I c (I CL ) & I c (I inj )

23. I-V characteristic of generator

24. SIS detector

25. Emission lines Different bias points along the semifluxon step Autonomous linewidth ~1.2 … 10 MHz

26. And now with PLL ;-) with PLL the spectral ratio is up to 97%

27. Summary & Problems Summary  many samples work (both generator and detector)  we observe expected operation:  a semifluxon step, SIS pumping  we have measured autonomous linewidth ..and linewidth with PLL Outlook (problems & todos):  maximum I c in I c (H) and I c (I inj ) are not equal  in high freq. setup strange shunt resistance of ~3 Ohm  in high freq. setup strange dep. of voltale on I inj.  Repeat again with remaining 2 samples and try to make new ones.  Compare linewidth with inj with the one with CL.  Compare with ZFS  not all LO freq were good