Rui-Hua Ni | Searcharxiv

arXiv2024

Observation of Quantized Klein Tunneling in a Dielectric Resonator Chain

We present the first experimental observation of quantized Klein tunneling in a bounded Dirac system, implemented by a dimer chain of dielectric microwave resonators. Both the unusual quantized levels and corresponding spinor states hybridized from distinct particle and hole wavefunctions are measured. All observations are in quantitative agreement with the hitherto-untested prediction of Dirac equation. Our results make an important step to realize and understand the particle-hole physics of Klein tunneling in bounded Dirac systems, and also shed light on potential applications for manipulating particle-hole hybridized spinor waves.

quant-ph↗

arXiv2023

Symmetry dictated universal helicity redistribution of Dirac fermions in transport

Helicity is a fundamental property of Dirac fermions. Yet, the general rule of how it changes in transport is still lacking. We uncover, theoretically, the universal spinor state transformation and consequently helicity redistribution rule in two cases of transport through potentials of electrostatic and mass types, respectively. The former is dictated by Lorentz boost and its complex counterpart in Klein tunneling regime, which establishes miraculously a unified yet latent connection between helicity, Klein tunneling, and Lorentz boost. The latter is governed by an abstract rotation group we construct, which reduces to SO(2) when acting on the plane of effective mass and momentum. They generate invariant submanifolds, i.e., leaves, that foliate the Hilbert space of Dirac spinors. Our results provide a basis for unified understanding of helicity transport, and may open a new window for exotic helicity-based physics and applications in mesoscopic systems.

cond-mat.mes-hall↗