arXiv subjects

E. C. I. Paterson

Publications and source records attributed to E. C. I. Paterson.

4 recordsLinked to original sources

arXiv2026

Dynamically tuneable helicity in twisted electromagnetic resonators

We report the generation of helical electromagnetic radiation in a microwave cavity resonator, achieved by introducing mirror asymmetry, i.e., chirality, through a controlled geometric twist of the conducting boundary conditions. The emergence of electromagnetic helicity is attributed to a nonzero spatial overlap between the electric and magnetic mode eigenvectors, quantified by $\text{Im}\left[\vec{\mathbf{E}}_i(\vec{r})\cdot{\vec{\mathbf{H}}}_i^*(\vec{r})\right]$, a feature not observed in conventional cavity resonators. This phenomenon originates from magnetoelectric coupling between nearly degenerate transverse electric (TE) and transverse magnetic (TM) modes, resulting in a measurable frequency shift of the resonant modes as a function of the twist angle, $ϕ$. In addition to the bulk helicity induced by global geometric twist, internal helical corrugations break structural symmetry on the surface, introducing an effective surface chirality $κ_{\text{eff}}$, which perturbs the resonant conditions and contributes to asymmetric frequency tuning. By dynamically varying $ϕ$, we demonstrate real-time, macroscopic manipulation of both electromagnetic helicity and resonant frequency. Furthermore, we investigate the underlying mode-coupling dynamics of the system, highlighting strong photon-photon interactions.

physics.optics↗

arXiv2026

Distinct Berry Phases in a Single Triangular Möbius Microwave Resonator

We report the experimental observation of two distinct Berry phases ($+\frac{2π}{3}$ and $-\frac{2π}{3}$) generated on the surface of a Möbius cavity resonator at microwave frequencies supporting the TE$_{1,0,n}$ mode family. This resonator consists of a twisted, mirror-asymmetric prism with a cross-section of the triangular $D_3$ symmetry group, bent around on itself to form a ring. This geometric class supports resonant modes with nonzero electromagnetic helicity (i.e. nonzero $\vec{E}\cdot\vec{B}$ product) at microwave frequencies. There exist modes with three-fold rotational symmetry as well as those that exhibit no rotational symmetry. The latter result in an accumulated Berry phase whilst the former do not, which is determined from the measured frequency shift of the modes when compared to a mirror-symmetric resonator of otherwise equivalent geometry.

physics.class-ph↗

arXiv2025

Electromagnetic Helicity in Twisted Cavity Resonators

Through left- or right-handed twisting, we investigate the impact of mirror-asymmetry (chirality) of the conducting boundary conditions of an equilaterial triangular cross-section electromagnetic resonator. We observe the generation of eigenmodes with non-zero electromagnetic helicity as a result of the coupling of near degenerate TE$_{11(p+1)}$ and TM$_{11p}$ modes. This can be interpreted as an emergence of magneto-electric coupling, which in turn produces a measurable shift in resonant mode frequency as a function of twist angle. We show that this coupling mechanism is equivalent to introducing a non-zero chirality material parameter $κ_\text{eff}$ or axion field $θ_{\text{eff}}$ to the medium. Our findings demonstrate the potential for real-time, macroscopic manipulation of electromagnetic helicity.

physics.class-ph↗

arXiv2023

Searching for Ultra-Light Axions with Twisted Cavity Resonators of Anyon Rotational Symmetry with Bulk Modes of Non-Zero Helicity

Möbius-ring resonators stem from a well-studied and fascinating geometrical structure that features a one-sided topology; the Möbius strip, and have been shown to exhibit fermion rotational symmetry with respect to a ring resonator with no twist (which exhibits boson rotational symmetry) (see PhysRevLett.101.247701). Here, we present a new type of resonator through the formation of twisted hollow structures using equilateral triangular cross-sections, which leads to the realization of a cavity with anyon rotational symmetry. Unlike all previous cavity resonators, the anyon resonator permits the existence of bulk resonant modes that exhibit non-zero electromagnetic helicity in vacuo, with a non-zero overlap of the electric and magnetic mode eigenvectors, $\int \mathbf{E}_p\cdot\mathbf{B}_p~dτ$, integrated over the cavity volume. In the upconversion limit, we show that these non-zero helical modes couple naturally to ultra-light dark matter axions within the bandwidth of the resonator by adding amplitude-modulated sidebands through the axion-photon chiral anomaly. Thus, we show a sensitive ultra-light dark matter experiment may be realized by implementing such a resonator in an ultra-stable oscillator configuration and searching for signals in the Fourier spectrum of amplitude fluctuations. This removes the typical requirement for an external magnetic field and therefore permits the use of superconducting materials to reduce surface losses and enhance sensitivity to axions.

hep-ph↗