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arXiv · 2602.08468

Observation of e/4 charge at $\nu=1/2$ in GaAs

Tomer Alkalai·Emily Hajigeorgiou·Adbhut Gupta·Tapas Senapati·Priya Tiwari·Chia-Tse Tai·Siddharth Kumar Singh·Kirk W. Baldwin·Loren N. Pfeiffer·Mansour Shayegan·Mitali Banerjee·Moty Heiblum
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Abstract

Even-denominator fractional quantum Hall states (FQHSs) fall outside the standard Laughlin's and Jain's odd-denominator hierarchy. In this work, we study the FQHS $\nu=1/2$ in the lowest Landau level. The state is confined within a 70 nm-wide GaAs quantum well, where the electrons exhibit a bilayer-like charge distribution. Inter-layer interactions stabilize the $\nu=1/2$ FQHS, which is predicted to host quasiparticles with charge e/4 - with either Abelian or non-Abelian topological order. Here, we report on shot-noise measurements of partitioned quasiparticles at $\nu=1/2$, where charge partitioning is generated by a unique etch-defined quantum point contact. Our measurements were performed on two nominally identical devices, at two independent experimental setups. Analysis of shot noise in the weak-backscattering regime in each device reveals quasiparticles with charge e/4. These observations provide a clear benchmark for future studies aimed at probing the topological order of the $\nu=1/2$ FQHS and its quasiparticles' exchange statistics.

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Tomer Alkalai, Emily Hajigeorgiou, Adbhut Gupta, Tapas Senapati, Priya Tiwari, Chia-Tse Tai, Siddharth Kumar Singh, Kirk W. Baldwin, Loren N. Pfeiffer, Mansour Shayegan, Mitali Banerjee, Moty Heiblum. 2026-02-09. Observation of e/4 charge at $\nu=1/2$ in GaAs. https://arxiv.org/abs/2602.08468

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