Abstract: Interference of electrons and anyons in the quantum Hall (QH) regime has always been of fundamental interest. Such measurements allow for studying the quantum statistics of quasiparticles. While a recent observation of fractional interference in a Fabry-Perot interferometer (FPI) was reported, fractional interference in a Mach-Zehnder interferometer (MZI) was never observed. The MZI is a true ‘two-path’ interferometer and is free of Coulomb interactions, thus responding solely to an Aharonov-Bohm (AB) phase.
In this talk, I will discuss an observation of AB interference of the outer-most edge mode v=1/3 in bulk filling v=2/5 in an MZI [1] with 2μm path length at ~10mK. While the maximum visibility of an interfering integer mode (outer-most mode at v=2) was ~91%, the corresponding visibility in the fractional regime was ~20%. With a pretty transparent QPCs of the v=1/3 mode (t>0.5), the partitioned, interfering, charge was found to be e*=e/3. As theoretically expected, a counter-intuitive flux periodicity was 0 – the flux quantum. This integer-like periodicity directly results from AB + braiding interference [2]. The MZI is topologically different from the FPI since one of its drains is enclosed inside the interfering loop – leading to this rather astonishing behavior. Moreover, the visibility of the interference oscillation was found (and understood) to be dramatically different than in FPI (or in the integer regime), peaking away from half transmission (in the integer case) of the MZI. This built-in braiding of the MZI offers new capabilities in testing exotic QH states.

1. Kundu, H.K., et al., Anyonic interference and braiding phase in a Mach-Zehnder interferometer. Nature Physics, 2023. 19, p. 515–521.
2. Law, K.T., D.E. Feldman, and Y. Gefen, Electronic Mach-Zehnder interferometer as a tool to probe fractional statistics. Physical Review B, 2006. 74(4): p. 045319.

Meeting ID: 972 0814 6371
Passcode: 944896