Is the fractional charge determined by the bulk or the edge?

  Sourav Biswas  ,  Rajarshi Bhattacharyya  ,  Moty Heiblum  ,  Vladimir Umansky  
Braun Center of Submicron Research, Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 761001, Israel

Fractionally charged quasiparticle excitation has long been detected via quantum shot-noise measurements, employing a quantum point contact (QPC) constriction, where weak backscattering occurs between two edges through a bulk residing in the QPC [1, 2]. Here, we report of the deterministic role of the bulk within the QPC constriction on the measured quasiparticle charge. The edge states are engineered at an interface between two quantum Hall bulk fillings, where independent tuning of each determines the character of the interface mode. Hence, the filling of the bulk within the QPC constriction and the filling of interface mode can be independently tuned. We observe that the quasiparticle charge, determined by partitioning at the QPC, depends only the bulk filling in the constriction, and is independent of the nature of the gapless chiral (interface) modes. This has important consequences on fractional interference, where determination of the interfering charge is crucial to reveal long sought anyonic statistics.



1)      R. de. Picciotto et al., Nature 389, 162 (1997).

2)      L. Saminadayar et al., Phys. Rev. Lett. 79, 2526 (1997).