Yukawa-Potential

The Yukawa potential ( after the Japanese physicist Hideki Yukawa, also called screened Coulomb potential ), the potential

Of the exchange particle mass as (see below) occur in the residual interaction of the strong interaction in superconductors. Yukawa showed in the 1930s that such a potential is generated by the exchange of pions between protons and neutrons.

This is

• The coupling strength of the interaction
• The velocity of light
• And the distance
• The reduced Planck constant.

The Yukawa potential is exponentially with increasing distance to zero. The range of the associated motor is of the order of the Compton wavelength of the exchange particles.

Coulomb potential and photon mass

In the limiting case, the Yukawa potential is in the Coulomb potential on how it is generated by massless photons, the exchange particle of the electromagnetic interaction. The photon had a mass, the electrostatic potential was no Coulomb potential, but a potential Yukawa. In all previous measurements ( in vacuum), the photon mass proved however to be below the detection limit.

In superconductors, however, occurs spontaneous symmetry breaking: a superconductor in a magnetic field displaces the magnetic field ( Meissner effect), the attenuation of the magnetic field is exponential. This can be interpreted that the photon in the superconductor is no longer massless. In the transition between vacuum and superconductor is the invariance to be able to choose at any place, the phase of the wave function arbitrarily broken by the fact that the Cooper pairs, the macroscopic wave function in superconductors characterized a phase.

• Nuclear physics