Magnonic Klein and acausal tunneling enabled by breaking the anti parity-time symmetry in antiferromagnets

Klein tunneling associated with particle-antiparticle pair productions across a potential barrier is a key prediction of quantum-field theory for relativistic particles. Yet, a direct experimental realization is hampered by the particles large rest mass resulting in high potential barrier. Here, for non-Hermitian antiferromagnets, at the verge of the anti-parity-time symmetry transition, chiral magnons are demonstrated to offer a bosonic platform to access Klein tunneling at meV energies in experimentally feasible settings. Our analytical and numerical simulations evidence that magnetic damping renders a low energy mechanism for the breakdown of the magnonic vacuum and for creating particle-antiparticle pairs in strong magnetic fields. Adopting Feynman's picture for antiparticles, the tunneling time of an incident magnon wave packet across a supercritical barrier is found to be negative. The uncovered aspects point to the potential of chiral magnons for addressing fundamental physics in a conceptually simple setup with the potential for use in chirality-dependent magnonic computing. Klein tunneling is associated with particle-antiparticle pair production across a potential barrier but observing the phenomenon experimentally is challenging. Using analytical and numerical simulations, the authors show how magnetic damping allows for the breakdown of magnonic vacuum and for the creation of particle-antiparticle pairs in non-Hermitian antiferromagnets in strong magnetic fields, which has relevance for chirality-dependent magnonic computing.

Automated summary

The authors use analytical and numerical simulations to demonstrate that magnetic damping in non-Hermitian antiferromagnets allows for the breakdown of magnonic vacuum and the creation of particle-antiparticle pairs in strong magnetic fields. This offers a platform for observing Klein tunneling at meV energies in experimentally feasible settings, with potential applications in chirality-dependent magnonic computing.