Observation of Gauge Field-Induced Non-Hermitian Helical Skin Effects

Synthetic gauge fields and non-Hermitian skin effects are central to topological phases and non-Hermitian physics, and each has recently attracted considerable interest across diverse research areas. Realizing skin effects typically requires asymmetric coupling or on-site gain and loss. Here, we theoretically and experimentally show that, under gauge fields, symmetry dissipative couplings can generate a nonreciprocal skin effect with a pseudospin degree of freedom and helical transport, which we term the “helical pseudospin skin effect”. Before introducing gauge fields, the model exhibits localized pseudospin edge modes and extended bulk modes without skin effects. As the gauge field strength increases from 0 to π, we observe the emergence of a non-Hermitian topological phase transition between hybrid- and second-order helical pseudospin skin effects. Our findings highlight gauge-fieldenriched non-Hermitian topology and introduces pseudospin-dependent accumulation into skin effects.