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A Kapitulnik

Publications and source records attributed to A Kapitulnik.

At least 19 recordsLinked to original sources
PubMed2003

Coexistence of periodic modulation of quasiparticle states and superconductivity in Bi2Sr2CaCu2O8+delta.

In this article we show, using scanning tunneling spectroscopy, the existence of static striped density of electronic states in nearly optimally doped Bi2Sr2CaCu2O8+delta in zero field. This modulation is aligned with the Cu-O bonds, with a periodicity of four lattice constants, and exhibits features characteristic of a two-dimensional system of line objects. We further show that the density of states modulation manifests itself as a shift of states from above to below the superconducting gap. The fact that a single energy scale (i.e., the gap) appears for both superconductivity and stripes suggests that these two effects have the same origin.

Journal Article↗
PubMed2003

New experimental constraints on non-Newtonian forces below 100 microm.

We have searched for large deviations from Newtonian gravity by means of a finite-frequency microcantilever-based experiment. Our data eliminate from consideration mechanisms of deviation that posit strengths approximately 10(4) times Newtonian gravity at length scales of 20 microm. This measurement is 3 orders of magnitude more sensitive than others that provide constraints at similar length scales.

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PubMed2000

Domain wall resistivity in SrRuO3.

SrRuO3 is an itinerant ferromagnet with T(c) approximately 150 K. When SrRuO3 is cooled through T(c) in zero applied magnetic field, a stripe domain structure appears whose orientation is uniquely determined by the large uniaxial magnetocrystalline anisotropy. We find that the ferromagnetic domain walls clearly enhance the resistivity of SrRuO3 and that the enhancement has different temperature dependence for currents parallel and perpendicular to the domain walls. We discuss possible interpretations of our results.

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PubMed1996

Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+delta

Angle-resolved photoemission experiments reveal evidence of an energy gap in the normal state excitation spectrum of the cuprate superconductor Bi2Sr2CaCu2O8+delta. This gap exists only in underdoped samples and closes around the doping level at which the superconducting transition temperature Tc is a maximum. The momentum dependence and magnitude of the gap closely resemble those of the dx2-y2 gap observed in the superconducting state. This observation is consistent with results from several other experimental techniques, which also indicate the presence of a gap in the normal state. Some possible theoretical explanations for this effect are reviewed.

Journal Article↗