, , <
Gad Koren
Prof. Emeritus
Topic:    Condensed Matter & Materials Physics
Office:Lidow Complex-Room:  364
Phone:  04-829-3552
Research Lab:Lidow Complex-Room:  234
Phone:  04-829-5907
Research Lab:Lidow Complex-Room:  119
Phone:  04-829-2027
Research Interests & Publications:  

High temperature superconductivity, thin films and junctions.
URL: http://physics.technion.ac.il/~gkoren/

Current and Recent Research:

In general, our group is investigating the properties of high temperature superconducting thin films, multilayers and junctions with various metallic and ferromagnetic interlayers or barriers. In the past three year we have carried out the following studies on: i) Characterization by scanning tunneling spectroscopy of the pseudogap and the x=1/8 anomaly in La2-xSrxCuO4 thin films [30]; ii)Penetration of Andreev bound states into a ferromagnet in SrRuO3/(110){tex}YBa_2 Cu_3 O_7-δ{/tex} bilayers [31]; iii) Tc enhancement in La1.65Sr0.35CuO4 - La2-xSrxCuO4 bilayers [34]; iv) Quantum vortex tunneling in YBa2Cu3O7-δ thin films [32]; v) Behavior of the ferromagnetic transition of SrRuO3 in nanometer thick bilayers with YBa2Cu3Oy, La1.88Sr0.12CuO4-y, Au and Cr, where a specific signature of injected carriers in the pseudogap regime was found [33]; vi) Proximity-Induced Pseudogap measurements where evidence for preformed pairs was found [39]; vii) Spatial modulation of midgap states in (001) La1.88Sr0.12CuO4 films where antiphase ordering of the d-wave order parameterwere observed [41]; and viii) Crossed Andreev effect in d-wave superconductorferromagnet junctions in the vicinity of domain walls [44].

* The reference numbers are from the list of publications below

Selected Publication:

    • G. Koren, E. Polturak, N. Levy and G. Deutscher, Angular Dependence of theCritical Current in Thin YBa2Cu3O7-δ Films with Unidirectional Nano-Cracks, Phys. Rev. B 61, 3734, (2000).

    • R. Carmi, E. Polturak, G. Koren, and A. Auerbach, Spontaneous MacroscopicMagnetization at the Superconducting Transition Temperature of YBa2Cu3O7-δ , Nature 404, 853-5, (2000).

    • R. Carmi, E. Polturak and G. Koren, Observation of Spontaneous Flux Generationin a Multi-Josephson-Junction Loop, Phys. Rev. Lett. 84, 4966-9 (2000).

    • A. Barman and G. Koren, Thickness-Dependent Transport Properties ofNd2/3Sr1/3MnO3 Thin Films, Appl. Phys. Lett. 77, 1674 (2000).

    • E. Polturak, G. Koren, I. Flohr, R. Waller and M. Guelman, Space-Based HighTemperature Superconductivity Experiment - Design and Performance, IEEETrans. Microwave Theory and Tech. 48, 1289 (2000).

    • A. Sharoni, G. Koren and O. Millo, Correlation of Tunneling Spectra with SurfaceNano-morphology and Doping in Thin YBCO Films, Europhys. Lett. 54, 675(2001).

    • A. Sharoni, O. Millo, A. Kohen, Y. Dagan, R. Beck, G. Deutscher, and G. Koren,Local and macroscopic tunneling spectroscopy of Y1-xCaxBa2Cu3O7-δ films:Evidence for a doping-dependent is or idxy component in the order parameter, Phys. Rev. B 65, 134526 (2002).

    • G. Koren and N. Levy, Experimental evidence for a small s-wave component inthe order parameter of underdoped YBCO, Europhys. Lett. 59, 121 (2002).

    • Gad Koren and Emil Polturak, Is LaAlO3 a Viable Substrate for the Deposition ofHigh Quality Thin Films of YBa2Cu3O7-δ ? Superconductors Science and Technology, 15, 1335 (2002).

    • D. E. Oates, M. A. Hein, P. J. Hirst, R. J. Humphreys, G. Koren, and E. Polturak, Non-linear microwave surface impedance of YBCO films, Physica C, 372-376, 462 (2002).

    • G. Koren, N. Levy and E. Polturak, Observation of three energy scales (energygaps) in the conductance of underdoped YBCO junctions, J. of Low Temp. Phys. 131, 849 (2003).

    • A. Sharoni, G. Leibovitch, A. Kohen, R. Beck, G. Deutscher, G. Koren and O.Millo, Scanning tunneling spectroscopy of a-axis YBa2Cu3O7-δ films: k-selectivityand the shape of the superconductor gap, Europhys. Lett. 62, 883 (2003).

    • A. Maniv, E. Polturak, and G. Koren, Observation of magnetic flux generatedspontaneously during a rapid quench of superconducting films, Phys. Rev. Lett. 91, 197001-4 (2003).

    • I. Lubimova and G. Koren, Simulations of experimental conductance spectra ofYBa2Cu3O7-δ junctions: Role of a long d-wave decay length and a small iscomponent in the pair potential near the interface, Phys. Rev. B 68, 224519-1(2003).

    • Amos Sharoni, Itay Asulin, Gad Koren and Oded Millo, Proximity effect in GoldCoated YBa2Cu3O7-δ films studied by scanning tunneling spectroscopy, Phys. Rev. Lett. 92, 017003-1 (2004).

    • B. Kalisky, Y. Wolfus, Y.Yeshurun, G. Koren, R. P. Huebener, I–V curves ofYBCO microbridges in the flux flow regime, Physica C, 401, 273-276 (2004).

    • G. Koren, L. Shkedy and E. Polturak, Observation of a common symmetry for thepseudogap and the superconducting order parameter in the a-b plane ofunderdoped YBCO, Physica C, 403, 45-51 (2004).

    • L. Shkedy, P. Aronov, G. Koren and E. Polturak, Observation of McMillan-Rowell like oscillations in underdoped YBCO junctions oriented along the node ofthe d-wave order parameter, Phys. Rev. B 69, 132507 (2004).

    • I. Asulin, A. Sharoni, O. Yuli, G. Koren and O. Millo, Anomalous Proximity effectin gold coated (110) YBCO films: Penetration of the Andreev bound states, Phys. Rev. Lett. 93, 157001 (2004).

    • D. E. Oates, S. H. Park, D. Agassi and G. Koren, Temperature dependence ofinter-modulation distortion in YBCO, Supercon. Sci. Technol. 17, S290 (2004).

    • D. E. Oates, S. H. Park and G. Koren, Observation of the nonlinear Meissnereffect in YBCO thin films: Evidence for a d-wave order parameter in the bulk ofthe cuprates, Phys. Rev. Lett. 93, 197001, (2004).

    • L. Shkedy, G. Koren and E. Polturak, Magnetoresistance of junctions made ofunderdoped YBCO separated by a Ga-doped YBCO barrier, Phys. Rev. B 71,134502 (2005).

    • A. Maniv, E. Polturak, G. Koren, Y. Bliokh, B. Biehler, B. U. Runge, P. Leiderer,B. Shapiro and I. Shapiro, Observation of a new mechanism of spontaneousgeneration of magnetic flux in a superconductor, Phys. Rev. Lett. 94, 247005 (2005).

    • D. E. Oates, S. H. Park, D. Agassi, G. Koren and K. Irgmaier, Temperaturedependence of intermodulation distortion in YBCO: Understanding nonlinearity, IEEE Trans. Appl. Superconductivity, 15, 3589 (2005).

    • I. Felner, G. Kopnov and G. Koren, Anisotropic magnetization ofRuEu1.5Ce0.5Sr2Cu2O10 (Ru-1222) thin films, Physica C, 432, 270 (2005).

    • P. Aronov and G. Koren, Signature of a crossed Andreev reflection effect (CARE)in the magnetic response of YBa2Cu3O7-δ junctions with the itinerant ferromagnet SrRuO3 , Phys. Rev. B 72, 184515 (2005).

    • G. Koren, P. Aronov and E. Polturak, Experimental search for anisotropic fluxflow resistivity in the a-b plane of optimally doped epitaxial thin films ofYBa2Cu3O7-δ , Phys. Rev. B 72, 212503 (2005).

    • B. Kalisky, P. Aronov, G. Koren, A. Shaulov, Y. Yeshurun and R. P. Huebener,Nonlinear Flux-flow resistivity anisotropy in the instability regime in the a-bplane of epitaxial thin films of YBa2Cu3O7-δ, Phys. Rev. Lett. 97, 67003 (2006).

    • I. Asulin, O. Yuli, G. Koren and O. Millo, Evidence for Crossed AndreevReflections in bilayers of (100) YBa2Cu3O7-δ and the itinerant ferromagnetSrRuO3, Phys. Rev. B 74, 092501 (2006).

    • O. Yuli, I. Asulin, O. Millo and G. Koren, Scanning tunneling spectroscopycharacterization of the pseudogap and the 1/8 anomaly in La2-xSrxCuO4 thin films, Phys. Rev B 75, 184521 (2007).

    • I. Asulin, O. Yuli, I. Felner, G. Koren and O. Millo, Penetration of Andreev boundstates into a ferromagnet in SrRuO3/(110)YBa2Cu3O7-δ bilayers, Phys. Rev. B 76, 64507 (2007).

    • G. Koren, Y. Mor, A. Auerbach and E. Polturak, Quantum vortex tunneling inYBa2Cu3O7-δ thin films, Phys. Rev. B 76, 134516 (2007).

    • G. Aharonovich, G. Koren and E. Polturak, Ferromagnetic transition of SrRuO3 innanometer thick bilayers with YBa2Cu3Oy La1.88Sr0.12CuO4-y, Au and Cr: Signatureof injected carriers in the pseudogap regime. Phys. Rev. B 76, 224514 (2007).

    • O. Yuli, I. Asulin, O. Milo, D. Orgad, L. Iomin and G. Koren, Enhancement of thesuperconducting transition temperature in La2-xSrxCuO4 bilayers: Role of pairingand phase stiffness, Phys. Rev. Lett. 101, 057005 (2008).

    • A. Kanigel, U. Chatterjee, M. Randeria, M. R. Norman, G. Koren, K. Kadowakiand J. C. Campuzano, Evidence for pairing above Tc from the electronicdispersion in the pseudogap phase of cuprates, Phys. Rev. Lett. 101, 137002, (2008).

    • I. Asulin, O. Yuli, G. Koren and O. Millo, Evidence for Induced Magnetization inSuperconductor-Ferromagnet Hetero-structures: a Scanning TunnelingSpectroscopy Study, Phys. Rev. B 79, 174524 (2009).

    • G. Koren and O. Millo, Conventional proximity effect in bilayers ofsuperconducting underdoped La1.88Sr0.12CuO4 islands coated with nonsuperconducting overdoped La1.65Sr0.35CuO4, Phys. Rev. B 80, 054507 (2009).

    • D. Golubchik, E. Polturak, G. Koren and S. G. Lipson, A high resolution magneto-optical system for imaging of individual magnetic flux quanta, Optics Express, 17, 16160 (2009).

    • Ofer Yuli, Itay Asulin, Yoav Kalcheim, Gad Koren, and Oded Millo, Proximity-Induced Pseudogap: Evidence for Preformed Pairs, Phys. Rev. Lett. 103, 197003(2009).

    • M. Shay, A. Keren, G. Koren, A. Kanigel, O. Shafir, L. Marcipar, G.Nieuwenhuys, E. Morenzoni, M. Dubman, A. Suter, and T. Prokscha, The Effectof Supercurrent on the Magnetic Phase Transition in High-Tc-Superconductors, Phys. Rev. B 80, 144511 (2009).

    • Ofer Yuli, Itay Asulin, Gad Koren, and Oded Millo, Spatial modulation of midgapstates in (001) La1.88Sr0.12CuO4 films: Indications for antiphase ordering of the dwaveorder parameter, Phys. Rev. B 81, 024516 (2010).

    • G. Koren and O. Millo, Enhancement of the superconducting transitiontemperature of La1-xSrxCuO4 and La1.875Ba0.125CuO4 bilayers: Bilayer andreference film prepared on the same wafer, Phys. Rev. B 81, 134516 (2010).

    • Daniel Golubchik, Emil Polturak, and Gad Koren, Evidence for long-rangecorrelations within arrays of spontaneously created magnetic vortices in a Nbthin-film superconductor. Phys. Rev. Lett. 104, 247002 (2010).

    • T. Kirzhner and G. Koren, Crossed Andreev effect in d-wave superconductorferromagnetjunctions in the vicinity of domain walls. Submitted to Phys. Rev. B. [cond-mat.supr-con arXiv:1006.0134v1]

    FaLang translation system by Faboba