Electromagnetic Signatures of Possible Charge Anomalies in Tunneling

MINOTTI, FERNANDO; MODANESE, GIOVANNI

Quantum Reports

MDPI

Año: 2022 vol. 4 p. 277 - 295

We reconsider some well-known tunneling processes from the point of view of Aharonov-Bohm electrodynamics, a unique extension of Maxwell´s theory which admits charge-current sources that are not locally conserved. In particular we are interested into tunneling phenomena having relatively long range (otherwise the non-Maxwellian effects become irrelevant, especially at high frequency) and involving macroscopic wavefunctions and coherent matter, for which it makes sense to evaluate the classical e.m. field generated by the tunneling particles. For some condensed-matter systems, admitting discontinuities in the probability current is a possible way of formulating phenomenological models. In such cases, the Aharonov-Bohm theory offers a logically consistent approach and allows to derive observable consequences. Typical e.m. signatures of the failure of local conservation are at high frequency the generation of a longitudinal electric radiation field, and at low frequency a small effect of ``missing´´ magnetic field. Possible causes of this failure are instant tunneling and phase slips in superconductors. For macroscopic quantum systems in which the phase-number uncertainty relation $Delta N Delta arphi sim 1$ applies, the expectation value of the anomalous source $I=partial_t ho + abla cdot mathbf{j}$ has quantum fluctuations, thus becoming a random source of weak non-Maxwellian fields.