Dresden 2026 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 83: Topology: Quantum Hall Systems

TT 83.9: Talk

Thursday, March 12, 2026, 17:15–17:30, HSZ/0105

Fractional Statistics in Anyon Colliders: A Keldysh-Instanton Approach — •Julian Kälber, Matthias Thamm, Felix Puster, and Bernd Rosenow — Universität Leipzig

The observation of fractional statistics in fractional quantum Hall (FQH) systems remains a central goal of modern condensed-matter physics. In recent collider-type experiments, dilute anyon beams are injected through quantum point contacts (QPCs) into unbiased edges, and signatures of anyonic exchange statistics are extracted from current cross-correlations. A quantitative description of these experiments, however, requires an accurate treatment of the QPCs, which act as dynamical tunnelling gates and introduce non-equilibrium effects that are not captured by simple Poissonian models.

In this work we develop an approximation scheme that incorporates the QPC dynamics within the Keldysh formalism. From the full action we derive an effective tunnelling action and obtain real-time instanton solutions of the free chiral-edge theory. The resulting non-equilibrium prefactor for tunnelling-operator correlation functions has the same structure as the Poissonian averaging employed in dilute-beam models, it reproduces the correct long-time asymptotics, and naturally generates oscillatory short-time features absent in previous treatments. Using this formalism we calculate a generalized Fano factor for a balanced anyon collider. The predicted values agree with theoretical expectations and with experimental measurements in the limit of small QPC transparencies, and remain consistent with experimental results at finite transparencies.

Keywords: Quantum Hall; Fractional Statistics; Anyon Collider; Keldysh Instantons