1. External synchronization Josephson oscillations in intrinsic stack of junctions under microwave irradiation and c-axis magnetic field I.F. Schegolev Memorial Conference (Chernogolovka 2009) Collaborators: K. Hirata, S. Ooi, T. Mochiku, National Institute for Materials Science, Superconducting Materials Center, Japan Yu.I. Latyshev, Institute of Radio-Engineering and Electronics, Russian Academy of Sciences, Russia Marat B. Gaifullin Department of Physics, Loughborough University, Loughborough, UK

2. OUTLINE 1.Introduction 2.Shapiro step observation in intrinsic stack of Josephson junctions 3.Damping regions of the vortex phase diagram in Bi 2 Sr 2 CaCu 2 O 8+  4. Shapiro steps observation in stack of up to 2500 junctions 5.Mechanism of the synchronization by c-axis magnetic field 6. Conclusion 2

3.  (0)/h  6.5THz,  c  1Å<<s=12Å and  c <<  ab, d=3Å <  =15Å Debye screening length,  = c / ab  100-1500, R.Kleiner, et.al., PRL 68, 2394 (1992) Oya G. et al. Japan. J. Appl. Phys. 31 L829 (1992) SIS junctions are strongly underdamped Josephson junction superlattice in Bi 2 Sr 2 CaCu 2 O 8+  Mc Cumber  approaches to 2000 3

4. Hysteretic I-V in zero field 20 x 8.8  m 2, N=670, T c =79.8K, J c =910A/cm 2 Stacked JJ are strongly underdamped in zero magnetic field. 4

5. Shapiro steps in zero magnetic field In intrinsic stack of Bi 2 Sr 2 CaCu 2 O 8+  N about 10% of all stack R.Kleiner, et.al., PRL 68, 2394 (1992)  m/w <  p 5

6. Experiments in damped resistively shunted stack in Bi 2 Sr 2 CaCu 2 O 8+  Wang H.B. et al. Physica C 362, 108 (2001) Shapiro step for only single junction of the stack was observed N =1, order of step  m/w <  p 6

7. Experiments at  m/w >>  p in zero magnetic field in hysteretic state in Bi 2 Sr 2 CaCu 2 O 8+  Without DC magnetic field Wang H.B. et al. PRL 87, 107002 (2001); Supercond. Sci. Technol. 15, 90 (2002) Shapiro steps were observed in strong hysteretic state on return current branch (one by one switching ) N – number junction in stack 7

8. Collective Shapiro steps on flux flow branch In strong 2.0T magnetic field parallel to ab-plane (B>  0 /  s 2 ) Yu.I.Latyshev, M.B.Gaifullin et al. PRL87, 247007 (2001) 8

9. Simple model for Resistively and Capacitively Shunted Junctions (RCSJ) where - period of Josephson oscillation at Mc Cumber-Stewart parameter is 9

10. Very hysteretic I-V in zero field I-V without hysteresis in field I-V measurements and H-T phase diagram 10

11. I-V hysteresis for underdoped sample in c -axis field 20 x 8.8  m 2, N=670, T c =79.8K, J c =910A/cm 2   chances abruptly crossing melting line in the region  p anomaly 11

12. Characterization of vortex phase diagram by Josephson plasma resonance Abrupt changes of crossing the phase transition lines M.B.Gaifullin, Y.Matsuda, et al., PRL 84, 2945 (2000) Y.Matsuda, M.B.Gaifullin, et al., PRL 75, 4512 (1995) underdoped sample 12

13. On chip characterization of vortex phase diagram by I-V measurements S.Ooi, T.Mochiku, K.Hirata Physica C 378-381, 523 (2002) 13

14. From Vortex Liquid to Bragg Glass by H scan at 55K Trajectory on phase diagram V st approaches to voltage of full stack sinchronization in BG phase 14

15. From Vortex Liquid to Vortex Glass by T scan at 0.4T V st approaches to voltage of full stack sinchronization in VG phase I-V hysteresis disappeared approaching VG phase Trajectory on phase diagram 15

16. From Vortex Glass to Bragg Glass by H scan at 35K Slightly overdoped sample 10.5 x 7.8  m 2, N=1270, T c = 90.5K, J c =1100A/cm 2 16

17. Collective Shapiro steps in c-axis magnetic field, N=460 Strongly underdoped sample, where  o - quantum flux; n – order of step; N – number junction in stack N is 100% junctions in stack 17

18. Collective Shapiro step in c-axis magnetic field, Bessel-like m/w power dependence Underdoped sample 20 x 8.8  m 2, N=670, T c = 79.5K, J c =910A/cm 2 18

19. Collective Shapiro step in c-axis magnetic field, Bessel-like m/w power dependence where C is the spatial layer to layer coherence factor 19

20. Collective Shapiro step in c-axis magnetic field with N=1270 Slightly overdoped sample 10.5 x 7.8  m 2, N=1270, T c = 90.5K, J c =1100A/cm 2 N = (100 +/- 1.2)% junctions in stack 20

21. Collective Shapiro step in c-axis magnetic field with N=2500 In overdoped sample 16 x 9.1 x 3.8  m 3, T c =85.5K, J c (0)=2130A/cm 2 N = (100 +/- 1.1)% junctions in stack. Overheating limited order of step to n=1 M.B.Gaifullin et.al., Physica C 468 (2008) 21

22. Wandering of the pancakes and field dependence McCumber parameter L.I.Glazman,A.E.Koshelev, PRB 43, 2835 (1991) L.N.Bulaevskii et al., PRL 74, 801 (1995) A. E. Koshelev, Phys. Rev. Lett. 77, 3901 (1996) In the vortex liquid state 22

23. Sample preparation and characterization Samples: Overdoped - cut from bulk of single crystal; Strongly underdoped – whickers Doping was confirmed from R(T), R(H) measurements; Size: from 1.2x2mkm^2 to 38x4.5mkm^2 ( L  J  to L>> J  ) N=60 to 2500, counted from sample thickness and branching on I-V Yu.I. Latyshev, S.-J. Kim, Yamashita, IEEE T. Appl. Supercond., 9, 4312 (1999) Structure was made by FIB two side processing method 23

24. BWO with frequency range 74 –136GHz; Max radiated m/w power 30mW. Josephson junction stack mounted on finline antenna in WR-10 waveguide, TE 01 mode Microwave setup 24

25. Summary 1. Intrinsic stacked Josephson junctions are significantly damped in c- axis magnetic field in the vortex liquid state and in the vortex glass state. 2.Synchronization of Josephson oscillations in intrinsic stack of junctions can be achieved for total number of junctions under external microwave irradiation in c-axis magnetic field. 3. Microscopically, wandering of pancakes is the main factor of the damping enhance and synchronization in the vortex liquid state Effectively, pancakes works as a shunts in every layer of Bi 2 Sr 2 CaCu 2 O 8+  25