Nanogallery
Nanogallery
TODAY SEPTEMBER 28, 2020

Historical note: Little-Parks effect

The curve represents the hystorical measurments of the LP oscillations
Little-Parks oscillation provides direct proof of the quantum behavior of electrons in a superconductor. In their experiments (1962), William A. Little and Roland D. Parks demonstrated that electrons forming a quantum-coherent condensate in superconducting metals exhibit sensitivity to the vector-potential, and not only to the magnetic field, as non-quantum charged particles do. Sensitivity to the vector-potential is a general signature of charged quantum particles related to the gauge invariance principle. Little and Parks showed that a large fraction of electrons in a superconductor behave essentially as a single quantum particle.
Little-Parks oscillation occurs in hollow superconducting cylinders pierced by a magnetic field. The critical temperature and thus the electrical resistance oscillate periodically as the magnetic field is gradually increased. The period is defined as the superconducting magnetic flux quantum h/2e divided by the area of the cross-section of the cylinder. Thus one period corresponds to an increase of the magnetic flux through the cylinder by one flux quantum h/2e. Based on quantum theory one expects that the LP oscillation of the critical temperature should occur even if the magnetic field is completely confined inside the superconducting cylinder, without entering into the walls of the cylinder. Testing this prediction experimentally is a challenging problem.
See also images:
William Little, one of the discoverers of the famous Little-Parks oscillations in superconductors.
William Little, one of the discoverers of the famous Little-Parks oscillations in superconductors.

Related Links:
  • W. A. Little, R. D. Parks, "Observation of quantum periodicity in the transition temperature of a superconducting cylinder," Phys. Rev. Lett. V.9, p.9-12 (1962)
  • Wikipedia--Little-Parks Effect
  • William A. Little
  • Ronald D. Parks
  • The cylindrical superstructures are composed of silver nanoparticles with V-shaped amphiphilic arms. The short rod-like and spherical assemblies are made of gold nanoparticles with the same V-shaped amphiphilic arms.  The self-assembly occurs upon slow addition of water to solution of nanoparticles in organic solvent called tetrahydrofuran. The resulting mixture is then dialyzed against pure water in order to remove organic solvent and obtain a pure aqueous solution of the superstructures (they remain in water without any precipitation, just like micelles).
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