Research Staff Member Emeritus, IBM Research Division
Visiting Scholar, University of Twente, Netherlands, April-June 2006
Visiting Scholar, Stanford University, January-March 2006
Research Staff Member, IBM Research Division (1978-2006)
Visiting Scholar, Stanford University, April 2003
Professeur Étranger, Université Joseph Fourier, Grenoble, France, March-May 1999
Post-doctoral fellow and research assistant professor, University of Pennsylvania (1976-1978)
Ph.D. Physics, University of California, Santa Barbara(1976)
B.A. Physics, University of California, Santa Barbara (1971)
Fellow - American Physical Society
Fellow - American Association for the Advancement of Science
1998 Oliver E. Buckley Prize of the American Physical Society
Address: 420 Heritage Hls Unit B, Somers, NY 10589-1983
Phone: (650) 492-5090
Email: kirtley@ucsbalum.net
Website:http://www.kirtleyscientific.com

Research Interests

• Scanning SQUID microscopy: For the past dozen years I have developed the technique of scanning SQUID microscopy and used the resulting novel instruments for fundamental studies. These studies included:
  • Phase sensitive pairing symmetry tests: Our experiments, which imaged the half-flux quantum effect in a tricrystal geometry, showed that the gap has predominantly d-wave symmetry in a number of the cuprate high-T_c superconductors over a broad range in doping and temperature.
    ``Symmetry of the order parameter in the high-Tc superconductor YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7 -δ</sub>", J.R. Kirtley, C.C. Tsuei, J.Z. Sun, C.C. Chi, Lock See Yu-Jahnes, A. Gupta, M. Rupp, and M.B. Ketchen, Nature 373,225(1995).
  • Interlayer tunneling model: By imaging interlayer vortices in single-layer cuprates, we showed that interlayer tunneling was an insufficiently strong mechanism to account for the high critical temperatures observed in these superconductors.
    ``Images of interlayer Josephson vortices in Tl₂Ba₂Cu O_{6 + δ}", K.A. Moler, J.R. Kirtley, D.G. Hinks, T.W. Li, and M. Xu, Science 279, 1193(1998).
  • Interacting pi-loop arrays: Superconducting pi-loops have a doubly degenerate ground state in zero applied fields, and interact with each other antiferromagnetically, providing a physical analog for the Ising spin model.
    ``Ordering and Manipulation of the Magnetic Moments in Large-Scale Arrays of Superconducting π-loops", Hans Hilgenkamp, Ariando, Henk-Jan Smilde, Dave H.A. Blank, Horst Rogalla, John R. Kirtley and Chang C. Tsuei, Nature 422 (6297), 50 (2003).
  • Quench cooled superconducting rings: Arrays of quenched superconducting rings provide a model system to test ideas about the early development of the universe. We found that the cooling dynamics of our rings was dominated by thermally activated processes.
    ``Thermally Activated Spontaneous Fluxoid Formation in Superconducting Thin-Film Rings", J.R. Kirtley, C.C. Tsuei, and F. Tafuri, Phys. Rev. Lett. 90 , 257001 (2003).
  • Angle-resolved, phase sensitive measurements of the in-plane gaps in YBCO : We have determined the position of the in-plane nodes in YBCO, and confirmed the small size, if any, of an imaginary component to the gap, by imaging the presence or absence of the half-flux quantum effect in a series of 2-junction YBCO-Nb rings with varying junction angles relative to the YBCO crystalline axes.
    ``Angle-resolved phase-sensitive determination of the in-plane gap symmetry in YBa₂Cu₃O₇", J. R. Kirtley, C. C. Tsuei, A. Ariando, C. J. M. Verwijs, S. Harkema and H. Hilgenkamp, Nature Physics 2 , 190 (2006).

    

    SQUID microscope images of a series of YBCO-Nb 2-junction rings. The transition between the presence and absence of spontaneous magnetization in the rings occurs when the junction normals are parallel to the nodes in the YBCO superconducting wave functions. This happens at angles slightly different from the (2m+1)45^o expected for a pure d-wave superconductor, and is a measure of the s-wave component to the gap.

• Previous work: I have also worked in a broad range of other areas in condensed matter physics:
  • Scanning tunneling potentiometry - I developed a new technique for measuring the electrochemical potential of a surface using a scanning tunneling microscope, and demonstrated a sensitivity approaching the Johnson noise limit.
    ``Direct measurement of potential steps at grain boundaries in the presence of current flow", J.R. Kirtley, S. Washburn, and M.J. Brady, Phys. Rev. Lett. 60 , 1546(1988).
  • Josephson junctions - We measured the intrinsic sub-gap dissipation in a Josephson junction by measuring the currents at which the junctions retrapped into the zero-voltage state from the voltage state.
    ``Measurement of the intrinsic subgap dissipation in Josephson junctions", J.R. Kirtley, C.D. Tesche, W.J. Gallagher, A.W. Kleinsasser, R.L. Sandstrom, S.I. Raider, and M.P.A. Fisher, Phys. Rev. Lett. 61 ,2372(1988).
  • Scanning tunneling microscopy - I built one of the first low-temperature scanning tunneling microscopes, and used it to make tunneling measurements of the energy gaps of the high T_c cuprate superconductors, including some of the first tunneling measurements of the gap in polycrystalline and single crystal YBa₂Cu₃O_7-δ.
    ``Tunneling and infra-red measurements of the superconducting energy gap in the high critical temperature superconductor Y-Ba-Cu-O", J.R. Kirtley, R.T. Collins, Z. Schlesinger, W.J. Gallagher, R.L. Sandstrom, T.R. Dinger, and D.A. Chance, Phys. Rev. B 35 ,8846(1987).
  • Electron heating in SiO<sub>2</sub> - We used surface plasmon mediated light emission from electron injector structures to measure electron heating in SiO<sub>2</sub>, and identified the role of acoustic phonon scattering in controlling electron ``runaway".
    ``Light emission from electron injector structures", T.N. Theis, J.R. Kirtley, D.J. DiMaria, and D.W. Dong, Phys. Rev. Lett. 50,750(1983).
    ``Strong electric field heating of conduction band electrons in SiO₂", T.N. Theis, D.J. DiMaria, and J.R. Kirtley, Phys. Rev. Lett. 52 ,1445 (1984).
  • Light emitting tunnel junctions - We demonstrated the role of fast surface plasmon and hot-electron effects using junctions on gratings.
    ``Diffraction grating enhanced light emission from tunnel junctions", J.R. Kirtley, T.N. Theis, and J.C. Tsang, Appl. Phys. Lett. 37 ,435(1980).
  • Surface enhanced Raman scattering - We demonstrated the role of surface plasmons using a tunnel junction geometry.
    ``Surface enhanced Raman scattering and surface plasmons", J.C. Tsang, J.R. Kirtley, and J.A. Bradley, Phys. Rev. Lett. 43 ,772 (1979).
  • Non-equilibrium superconductivity - We performed the first double junction geometry measurements of quasiparticle lifetimes and energy distributions.
    ``Experimental determination of the quasiparticle energy distribution in a non-equilibrium superconductor", S.B. Kaplan, J.R. Kirtley, and D.N. Langenberg, Phys. Rev. Lett. 39,291(1977).
  • Inelastic electron tunneling spectroscopy - Part of my thesis was a theory for molecular vibrational mode intensities in planar junction IETS.
    ``Theory of vibrational mode intensities in inelastic electron tunneling spectroscopy", John Kirtley, D.J. Scalapino, and P.K. Hansma, Phys. Rev B 14 ,3177(1976).