Observation of supersensitivity of non-Hermitian skin effect

Non-Hermitian systems exhibit an extraordinary sensitivity to boundary conditions, with a notable example being the non-Hermitian skin effect (NHSE), where a significant number of eigenstates accumulate at their open boundaries. In this work, we reveal a supersensitivity feature associated with the NHSE. In an acoustic system with dissipative couplings that preserve the anomalous time-reversal symmetry, we observe a <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mi>k</a:mi> </a:math> -dependent skin effect, in which acoustic waves localize at either the left or right open boundaries depending on the perpendicular wave vector. Remarkably, this supersensitivity is so extreme that adding a single unit to one boundary transforms the skin effect from bidirectional to unidirectional. More intriguingly, introducing another single unit to the opposite boundary can restore the original bidirectional skin effect. We directly observe this supersensitivity by detecting acoustic field distributions, consistent with theoretical predictions. Our findings offer a powerful approach to non-Hermitian manipulation and pave the way for high-sensitivity measurement using non-Hermitian systems.