Aolong Guo | Searcharxiv

arXiv2026

Constructing Exceptional Knots and Links with Arbitrary Braiding Topology

Exceptional knots and links represent a remarkable class of non-Hermitian metals in which exceptional degeneracies form knotted or linked manifolds in momentum space. Here, we report a universal construction framework for realizing exceptional knots and links with arbitrary braiding topology in 3D minimal two-band non-Hermitian systems. Our approach combines braid theory with semiholomorphic polynomials to establish a direct correspondence between braid words and non-Hermitian Bloch Hamiltonians. This framework enables the realization of a broad variety of exceptional configurations, including torus knots, lemniscate knots, nonfibred knots, hyperbolic knots, and multi-component links, within explicit tight-binding Hamiltonians. Furthermore, we demonstrate controllable topological transitions in which exceptional knots can be continuously untied through redistribution and reconnection of exceptional points, accompanied by transient exceptional chains and changes in spectral complex energy braiding. Our results establish a universal route toward programmable non-Hermitian knot topology and provide a versatile platform for exploring knotted band degeneracies and their associated physical phenomena across photonic, acoustic, mechanical, and cold-atom systems.

cond-mat.mes-hall↗

arXiv2024

Searching for Exotic Spin-Dependent Interactions with Diamond-Based Vector Magnetometer

We propose a new method to search for exotic spin-spin interactions between electrons and nucleons using a diamond-based vector magnetometer. The vector magnetometer can be constructed from ensembles of nitrogen-vacancy centers along different axes in a diamond. The $^{14}\mathrm{N} $ nuclear spins of nitrogen-vacancy centers in the same diamond can be polarized through the dynamic nuclear polarization method to serve as spin sources. With the vector magnetometer, the sought-after exotic interactions can be distinguished from the magnetic dipole-dipole interaction. For the axion-mediated interaction $ V_{PP} $, new upper bounds of the coupling $ |g_{P}^{e} g_{P}^{N}| $ are expected within the force range from 10 nm to 100 $ μ$m. For the $ Z' $-mediated interaction $ V_{AA} $, new upper bounds of the coupling $ |g_{A}^{e} g_{A}^{N}| $ are expected within the force range from 10 nm to 1 cm. The new upper bounds for $ V_{PP} $ and $ V_{AA} $ are both expected to be more than 5 orders of magnitude more stringent than existing constraints at the force range of 1 $ μ$m with the total measurement time of one day.

hep-ex↗