We report resonant tunneling experiments in a quantum antidot sample in the integer quantum Hall regime. In particular, we have measured the temperature T dependence of the peak value of a conductance peak on the i = 2 plateau, where there are two peaks per magnetic flux quantum straight phi(0). We observe a T-1 dependence as expected when tunneling through only one electron state is possible. This result is incompatible with tunneling through a compressible ring of several degenerate states. We also observe, for the first time, three conductance peaks per straight phi(0) on the i = 3 plateau.

A Quantum Antidot electrometer has been used in the first direct observation of the fractionally quantized electric charge. In this paper we report experiments performed on the integer i = 1, 2 and fractional f = 1/3 quantum Hall plateaus extending over a filling factor range of at least 27%. We find the charge of the Laughlin quasiparticles to be invariantly e/3, with standard deviation of 1.2% and absolute accuracy of 4%, independent of filling, tunneling current, and temperature.PACS numbers: 73.40. Hm, 73.40.Gk, 71.10.Pm The most fundamental aspect of the quantum Hall effect (QHE) is the constancy of the Hall conductance over a finite range of the filling factor ν. [1-3] Indeed, this property defines the phenomenon of QHE, and the quantized value of the Hall conductance σ xy of a particular QH state in units of e 2 /h is a principal quantum number of that QH state i or f , called "exact filling". Specifically, the electric charge of the quasiparticles is expected to be determined by the relevant quantum numbers, including i or f , and thus not expected to vary on a QH plateau as ν is varied from the exact filling. [3][4][5] On a QH plateau the charge of quasiparticles localized in the interior of a two dimensional electron system (2DES) is well defined. [6] In the case of the integer QH plateau at ν ≈ i the quasielectrons are simply electrons in the Landau level i + 1, and the quasiholes are the holes in the i th level. It is easy to understand the properties of FQHE quasiparticles using composite fermions. [7,8] In the case of the FQH plateau at f = i 2pi+1 quasielectrons are composite fermions (an electron binding 2p vortices) in the "Landau level" i + 1 of composite fermions, and the quasiholes are the holes in the i th level. It has been predicted theoretically that the electric charge of these quasiparticles is q = e 2pi+1 , positive for the quasiholes and negative for quasielectrons. [9,3] This fascinating fractional quantization of electric charge is a fundamental property of the strongly correlated FQH fluid.Although six years have passed since the first direct observation of 1 3 e particles in quantum antidot (QAD) electrometer experiments [10] one crucial aspect of theory remained untested: the invariance of charge at ν far from exact filling. In this paper we report experiments performed on the integer i = 1, 2 and fractional f = 1 3 quantum Hall plateaus which extend over a filling factor ν range of 27% to 45%. The charge of the QAD-bound quasiparticles has been measured to be constant, independent of ν over the entire plateau extent, with relative accuracy of ±1.2% and absolute accuracy of 4%. In addition, we observe no variation of the quasiparticle charge upon variation of temperature or applied current, in the experimentally accessible range.The QAD electrometer is illustrated in Fig. 1. [10,11] The antidot is defined lithographically in a constriction between two front gates in a 2DES. The antidot and the front gates create depletion potential hills in the 2DES plane and, in quantizing ma...

No abstract