John R. Kirtley

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Pairing symmetry in the cuprate superconductors is an important and controversial topic. The recent development of phase-sensitive tests, combined with the refinement of several other symmetry-sensitive techniques, has for the most part settled this controversy in favor of predominantly d-wave symmetry for a number of optimally holeand electron-doped(More)
The physics of the superconducting state in two-dimensional (2D) electron systems is relevant to understanding the high-transition-temperature copper oxide superconductors and for the development of future superconductors based on interface electron systems. But it is not yet understood how fundamental superconducting parameters, such as the spectral(More)
The phase of the macroscopic electron-pair wavefunction in a superconductor can vary only by multiples of 2pi when going around a closed contour. This results in quantization of magnetic flux, one of the most striking demonstrations of quantum phase coherence in superconductors. By using superconductors with unconventional pairing symmetry, or by(More)
We have combined a novel low temperature positioning mechanism with a single-chip miniature superconducting quantum interference device ~SQUID! magnetometer to form an extremely sensitive new magnetic microscope, with a demonstrated spatial resolution of ;10 mm. The design and operation of this scanning SQUID microscope will be described. The absolute(More)
Magnetic flux in superconductors is usually quantized in units of h/2e. Here we report scanning SQUID and scanning Hall probe studies of single fluxoids in high purity YBa2Cu3O6.35 crystals (T(c) less, similar 13 K), extending flux quantization studies to a region of the cuprate phase diagram where the superfluid density is sufficiently low that novel(More)
K. H. Kuit,1 J. R. Kirtley,1,2,3 W. van der Veur,1 C. G. Molenaar,1 F. J. G. Roesthuis,1 A. G. P. Troeman,1 J. R. Clem,4 H. Hilgenkamp,1 H. Rogalla,1 and J. Flokstra1 1Low Temperature Division, Mesa+ Institute for Nanotechnology, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands 2Department of Applied Physics, Stanford University, Palo(More)
Monodisperse magnetic nanoparticles (NPs) could enable the ultra-sensitive magnetic detection of biological analytes. However, rendering these particles biocompatible has remained a challenge. We report the bio-functionalization and detection of 12-nm manganese ferrite NPs. We have achieved the site-specific binding of biotin-functionalized NPs onto(More)
The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements(More)
The ability to control materials properties through interface engineering is demonstrated by the appearance of conductivity at the interface of certain insulators, most famously the {001} interface of the band insulators LaAlO3 and TiO2-terminated SrTiO3 (STO; refs 1, 2). Transport and other measurements in this system show a plethora of diverse physical(More)
The scanning SQUID microscope (SSM) is a powerful tool for imaging magnetic fields above sample surfaces. It has the advantage of high sensitivity and bandwidth and the disadvantages of relatively modest spatial resolution and the requirement of a cooled SQUID sensor. We describe the various implementations of this type of instrument and discuss a number of(More)