Aharonov-Bohm interference in even-denominator fractional quantum Hall states.
basic_science · Level V
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- Record sourced from PubMed, PMID 41501197.
- Also identified by DOI 10.1038/s41586-025-09891-2 and PMC identifier 12779543.
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Abstract
Position exchange of non-Abelian anyons affects the quantum state of their system in a topologically protected way<sup>1</sup>. Their expected manifestations in even-denominator fractional quantum Hall (FQH) systems offer the opportunity to directly study their unique statistical properties in interference experiments<sup>2</sup>. Here we present the observation of coherent Aharonov-Bohm interference at two even-denominator states in high-mobility bilayer-graphene-based van der Waals (vdW) heterostructures by using the Fabry-Pérot interferometry technique. Operating the interferometer at a constant filling factor, we observe an oscillation period corresponding to two flux quanta inside the interference loop, ΔΦ = 2Φ<sub>0</sub>, at which the interference does not carry signatures of non-Abelian statistics. The absence of the expected periodicity of ΔΦ = 4Φ<sub>0</sub> may indicate that the interfering quasiparticles carry the charge <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msup><mrow><mi>e</mi></mrow> <mrow><mo>*</mo></mrow> </msup> <mo>=</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>2</mn></mrow> </mfrac> <mi>e</mi></mrow> </math> or that interference of <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msup><mrow><mi>e</mi></mrow> <mrow><mo>*</mo></mrow> </msup> <mo>=</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>4</mn></mrow> </mfrac> <mi>e</mi></mrow> </math> quasiparticles is thermally smeared. Notably, at two hole-conjugate states, we also observe oscillation periods of half the expected value, indicating interference of <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msup><mrow><mi>e</mi></mrow> <mrow><mo>*</mo></mrow> </msup> <mo>=</mo> <mfrac><mrow><mn>2</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> <mi>e</mi></mrow> </math> quasiparticles instead of <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msup><mrow><mi>e</mi></mrow> <mrow><mo>*</mo></mrow> </msup> <mo>=</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>3</mn></mrow> </mfrac> <mi>e</mi></mrow> </math> . To investigate statistical phase contributions, we operated the Fabry-Pérot interferometer (FPI) with controlled deviations of the filling factor, thereby introducing fractional quasiparticles inside the interference loop. The resulting changes to the interference patterns at both half-filled states indicate that the extra bulk quasiparticles carry the fundamental charge <math xmlns="http://www.w3.org/1998/Math/MathML"> <mrow> <msup><mrow><mi>e</mi></mrow> <mrow><mo>*</mo></mrow> </msup> <mo>=</mo> <mfrac><mrow><mn>1</mn></mrow> <mrow><mn>4</mn></mrow> </mfrac> <mi>e</mi></mrow> </math> , as expected for non-Abelian anyons.