Vortex matter in HTS Grain Boundary Josephson Junctions: Intrinsic and Extrinsic d-wave Effects

Transcription

1 Vortex matter in HTS Grain Boundary Josephson Junctions: Intrinsic and Extrinsic d-wave Effects Francesco Tafuri INFM Coherentia Seconda Università di Napoli In collaboration with: J. Kirtley and C. Tsuei, IBM T.J. Watson Research Center F. Lombardi and T. Bauch, Chalmers University A. Barone, F. Miletto, D. Stornaiuolo and U. Scotti, Napoli Federico II E.Ilichev, IPHT Jena G. Balestrino, P.G. Medaglia, P. Orgiani, Roma Tor Vergata

2 Vortex matter d-wave OP symmetry search for spontaneous currents in HTS and HTS JJ (π-ring) Novel devices exploiting d-wave OP (π-circuitry) and possibly truly quantum effects π-junctions Flux dynamics Pearl vortices Vortex quantum tunneling Phase transition Cosmological experiments Topological defects Background and motivation d-wave OP symmetry Quantum effects HTS JJ

3 Half flux quantum effect inyb 2 C 3 O 7-x B= 0 mg B= 3.7 mg C. Tsuei, J. Kirtley et al. PRL ( 94) J. Kirtley, C. Tsuei et al. Nature ( 97)

4 π I C = I Co sin (π ϕ) I C = I Co sin ϕ 0 Josephson Effect and π-phase shift L.N. Bulaevskii, V.V. Kuzii and A.A. Sobyanin, JETP Lett. 25, 290 (1977) V.B. Geshkenbein, A.I. Larkin and A. Barone, Phys. Rev. B 36, 235 (1987) M. Sigrist and T.M. Rice, J. Phys. Soc. Jpn. 61, 4283 (1992) + Φ Φ Φ Φ Φ Φ Φ = Φ Φ ϕ π π o o c o a o o L I L U 2 cos 2 ), ( 2 2 D.Van Harlingen. Rev. Mod. Phys. 67, 515( 95)

5 Spontaneous nucleation of topological defects in phase transition (normal-superconductor) Amorphous Mo 3 Si superconducting thin film Optical Microscope Scanning SQUID Microscope T c = 7.81 K; 50 nm thick; 30 µm Outer Diameter, 20 µm Inner Diameter, 60 µm spacing

6 Spontaneous (Φ=0) nucleation of topological defects in Mo 3 Si rings Dependence on the cooling rate 2.1x10-4 K/sec 9.2x10-3 K/sec 21 K/sec

7 Probability of Mo 3 Si rings having a final fluxoid +1 as a function of the cooling rate Zero field cooling

8 Cosmological experiments in condensed matter systems Kibble-Zurek mechanism Keywords: Topological defects; Superfluids; Symmetry breaking dynamics; Vortex lines; Cosmological phase transitions Second order phase transition -equilibrium correlation length diverges; True correlation length ξ cannote be infinite -reaches maximum value ξ Correlated domains of diameter ξ Vortices where these domains meet T. Kibble, J. Phys. A 9, 1387 (1976). W. Zurek, Nature 317, 505 (1985); Physics Reports 276, 177 (1996)

9 Quantum computation L.B. Ioffe, V.B. Geshkenbein, M.V. Feigel'man, A.L. Fauchere, and G. Blatter. Nature 398, 679 (1999) Pre-requisites -tunnel junctions-low dissipation -doubly degenerate states -tunability of π-component -macroscopic quantum effects qubit condenses most of aspects related to unconventional order parameter symmetry and quantum effects Andreev bound states Time reversal symmetry breaking Imaginary component of OP,... Gap... A. Zagoskin, Cond. Mat (1999)

10 d-wave effects in JJ: the extreme case of 45 asymmetric configuration (θ( L =0 θ R =90 ): second harmonic and Andreev bound states D N S A1 e h A h e Relatively easy access to second harmonic a price to pay for instance: C.R. Hu, Phys. Rev. Lett. 72, 1626 (1994 ); T.Lowfander, V.S. Shumeiko and G. Wendin, Supercon. Sci. Technol. 14, R53 (2000); G. Blatter, V. B. Geshkenbein and L. B. IoffePhys. Rev. B 63, (2001)

11 d-wave effects in JJ: for instance π-loops and faceting GB facets Macroscopic GB π J. Mannhart, H.Hilgenkamp, B. Mayer, Ch. Gerber, J.R. Kirtley, K.A. Moler and M. Sigrist,Phys. Rev. Lett. 77, 2782 (1996);

12 Grain boundary techniques H.Hilgenkamp and J. Mannhart, Rev. Mod. Phys. (2002)

13 BP MgO vs BP CeO 2 : 0 vs π tilt twist c c b a a (001) YBCO c tilt + tilt b (001) YBCO twist - tilt AGB twist + tilt (110) MgO c (103) YBCO c (103) YBCO F. Tafuri, F. Carillo, F. Lombardi,F. Miletto Granozio, F. Ricci, U. Scotti di Uccio, A. Barone, G. Testa, E. Sarnelli and J.R. Kirtley, Phys. Rev. B 62, (2000).

14 TEM: clean basal plane GB (45 tilt)

15 I(mA) Anisotropy MgO vs CeO 2 in the extreme cases of tilt and twist Twist Tilt (Ix10) Tilt-tilt V(mV) I (µa) twist α=90 tilt α= (001) V (mv) (103) θ Twist-tilt

16 Transport properties in presence of H 100 T= 4.2 K 2.0x10-6 BP twist 20 µm; T = 800 mk 1.5x10-6 I (µa) I C (A) 1.0x x x x H (G) V (mv) -1.5x x10-6 critical current retrapping current B (µt)

17 Anisotropy in CeO 2 :Jc vs θ... intrinsic d-wave effects in all HTS single junctions J C vs θ Tilt-tilt θ Twist-tilt (001) YBCO (001) YBCO film (100)/(010) Y (010)/(100) Y J C (A/cm 2 ) 5x10 2 3x10 2 2x10 2 T = 4.2 K Bp CeO 2 Bp MgO (103) YBCO (103) YBCO film c) π/4 π/2 1.6 Angle (rad)

18 Intrinsic d-wave effects: angular dependence of J C 1.0 MAX I C / I C BP 10µm BP 4µm d-wave S-R modified d-wave θ (degrees) B C D A

19 YES Spontaneous currents NO

20 Biepitaxial vs other GBs Modelling: : long junction Our data J. Kirtley, K. Moler and D. Scalapino, PRB (1997) H.Hilgenkamp and J. Mannhart, Rev. Mod. Phys. (2002) F. Tafuri,, J. Kirtley, F. Lombardi and F. Miletto Phys. Rev. B (2003)

21 Families of vortices in a biepitaxial sample including closed geometry θ

22 a b θ twist-tilt Half flux quantum Effect: manipulation along BP GBs JJ c d

23 Paramagnetic signal (RF) along a GB line and absence of spontaneous currents (SSM) C T T (K) µm x 400 µm 600 µm x 400 µm (001) (103) (103) Finite H Phase angle α between drive current I rf and tank voltage L eff effective inductance R eff effective resistance if R eff does not depend on H dc (001) Q quality factor k coupling tank coil sample χ m ac magnetci susceptibitity 200 µm x 200 µm H = 0 (103)

24 Paramagnetic signal (RF) and absence of spontaneous currents (SSM) : possible hint for Andreev bound states in biepitaxial JJ??!! GB facets Macroscopic GB π - + D N S + - A1 e h A2 Presence of a mechanism able to split the midgap states, to populate the midgaps states unequally ± k y h e Higashitani, J. Phys. Soc. Jap. 66, 2556 ( 97); C.R. Hu, Phys. Rev. Lett. 72, 1626 (1994 ); T.Lowfander, V.S. Shumeiko and G. Wendin, Supercon. Sci. Technol. 14, R53 (2000) ANDREEV BOUND STATES

25 Flavour of d-wave induced effects 1.0 I C / I C MAX θ (degrees) BP 4µm BP 10µm d-wave S-R modified d-wave junctions with intrinsic Half flux quantum effect d-wave induced effects without necessarily extrinsic effects (additional noise) Andreev bound states intrinsic Intrinsic and extrinsic extrinsic Jc

26 Hysteretic behavior-switching currents Bp twist 90 0 w=20 µm T = 4.2 K critical current retrapping current I (µa) I C (µa) B (µt) V (µv) J C (A/cm 2 ) 5x Bp CeO 2 Bp MgO 3x x10 2 T = 4.2 K π/4 π/2 1.6 T T = = 4.2 K Angle (rad) 10 3 F. Lombardi, T. Bauch et al. Unpublished (2003)

27 Doubly degenerate states and π loops L.B. Ioffe, V.B. Geshkenbein, M.V. Feigel'man, A.L. Fauchere, and G. Blatter. Nature 398, 679 (1999); G. Blatter, V. B. Geshkenbein and L. B. IoffePhys. Rev. B 63, (2001) 2 1 I (µa) 0-1 twist, T = 25 mk V (mv) I C / I C MAX θ (degrees) BP 4µm BP 10µm d-wave S-R modified d-wave A B C D

28 An example of novel approaches to HTS junctions 150 nm GB 8 nm GB

29 5 CR 2 IL 5 CR Ba Ca CuO 2 Planes 6.4 Å 2 CR 2 CR # cell 5x2x5 Λ 17.6 Å # cells 4x2 Λ 6.4 Å 8.8 Å # cells 2x2 F. Tafuri, J. Kirtley, P.G. Medaglia, P.Orgiani and G. Balestrino, submitted (2003)

30 Evidence of vortex broadening for decreasing d Pearl length Λ = 2 λ 2 L / d

31 Hints for Josephson-like behavior 200 µm x 200µm 0-24 asymmetric symmetric GB I (ma) mm wide 5mm wide 5mm wide with H V(mV) T = 4.2 K

32 Vortex matter HTS JJ d-wave OPS Quantum effects 2 I C / I C MAX θ (degrees) BP 4µm BP 10µm d-wave S-R modified d-wave π-junctions Intrinsic d-wave d effects I (µa) twist, T = 25 mk V (mv) Pre-requisites requisites -tunnel junctions...low dissipation -doubly degenerate states -tunability of π-component -macroscopic quantum effects Novel devices exploiting d-wave d OP (π-circuitry)( and possibly truly quantum effects