Measuring the fundamental exchange phase of anyons in a modified quantum Hall interferometer

Quantum Hall interferometers combine the utility of chiral edge states and the natural presence of novel quasiparticle excitations to enable the direct measurement of quantum exchange statistics that extend beyond those of fermions and bosons. Recent demonstrations have shown that such devices constructed with various two-dimensional electronic systems have succeeded in measuring the abelian variant of anyon exchange statistics in Fabry-Perot interference in odd-denominator fractional quantum Hall (FQH) states. However, by the principle of operation of Fabry-Perot interferometer geometries, these studies in fact measured twice the fundamental exchange, giving an ambiguity for the true value [1]. A theoretical proposal recently put forward rectifies this by establishing a quantum (anti)dot structure within one of the quantum point contacts (QPC) that defines the device [2]. A discrepancy in the two possible tunneling processes through the dot adds a term to the interference signal that is dependent only on the single exchange phase. We report on observing the fundamental exchange in nu = 1/3 for the first time by achieving the proposed modified interferometer in a fully-tunable graphene device.

[1] N. Read and S. Das Sarma, Clarification of braiding statistics in Fabry–Perot interferometry (2023), Nat. Phys. 20 381–382.

[2] S. A. Kivelson and C. Murthy, A modified interferometer to measure anyonic braiding statistics (2024), arXiv:2403.12139 [cond-mat]