Abstract
We propose a new method, using the Andreev reflection at superconductors, to measure parity violation induced by the standard electroweak theory, which in turn constrains the possible parity-violating effects of new physics. The weak neutral currents induce parity-violating, marginal effective operators, though quite tiny, in superconductors. We estimate their effects on superconducting gaps and propose a method to measure the parity-violation from the spin polarization effect, when electrons or holes get Andreev-reflected at the interface between normal metal and a superconductor. Such polarization effects might be comparable to the atomic parity violation and thus naturally give an interesting bound on certain models of new physics, that couples to electrons, such as Majorana mass of active neutrinos or doubly charged Higgs.
Highlights
Weak interaction is the only fundamental force, known to break parity
The striking phenomena of parity non-conservation in the electroweak process are prominent in deep inelastic scattering of neutrinos off nucleons, that confirms the existence of the weak neutral currents, as predicted by the standard model of particle physics [1, 2]
The pari ‘ty violation effect is very difficult to detect at long distances, because the weak interaction is of very short range
Summary
The parity is broken at the fundamental level, as the standard electroweak theory, that unifies the weak and electromagnetic forces, is chiral. The observation of atomic parity violation (APV) has confirmed the standard electroweak theory and highly constrains possible new physics beyond the standard model [7,8,9], which might produce a large parity-violation at low energy. We first estimate the effect of the parity-violating standard electroweak theory in the Cooper-paring gap and propose as its observable consequences the spin-polarization of electrons or holes, when they get Andreev-reflected at the interface of metal and superconductor. We consider the new physics effects due to the Majorana mass of active neutrinos and the extended Higgs sector of the standard model, whose effects on the superconductivity possibly enhance the parity-violation. We show that new physics models such as the minimal model of type II seesaw [11, 12] or models with Majorana particles can be stringently constrained
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