Abstract
The pairing of composite fermions (CFs), i.e., electron-flux quasiparticles, is commonly proposed to explain the even-denominator fractional quantum Hall state observed at in the first excited Landau level (LL) of a two-dimensional electron system (2DES). While well established to exist in the lowest LL, much is unknown about CFs in the LL. Here we carry out geometric resonance measurements to detect CFs at by subjecting the 2DES to a one-dimensional density modulation. Our data, taken at a temperature of 0.3 K, reveal no geometric resonances for CFs in the LL. In stark contrast, we observe clear signatures of such resonances when is placed in the LL of the antisymmetric subband by varying the 2DES width. This finding implies that the CFs' mean free path is significantly smaller in the LL compared to the LL. Our additional data as a function of in-plane magnetic field highlight the role of subband index and establish that CFs at in the LL are more anisotropic in the symmetric subband than in the antisymmetric subband.
- Received 28 December 2016
DOI:https://doi.org/10.1103/PhysRevB.95.165438
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