arXiv subjects

V. Umansky

Publications and source records attributed to V. Umansky.

76 records · Page 5Linked to original sources

arXiv1999

Observation of a Fifth of the Electron Charge

We report the observation of quasi-particles with a charge q=e/5 detected by shot noise measurements in the 2/5 conducting channel (filling factor 2/5). This is in agreement with previous measurements that showed that the current in the lower, 1/3, channel is carried by quasiparticles with a charge q=e/3. These results demonstrate that the actual fraction of the charge can be different from the filling factor. Moreover, we show that there is no strong interaction between the channels, which can be considered as conducting the current independently.

cond-mat.mes-hall↗

arXiv1997

Dephasing due to Which Path Detector

We study dephasing of electrons induced by a which path detector and thus verify Bohr's complementarity principle for fermions. We utilize a double path interferometer with two slits, with one slit being replaced by a coherent quantum dot (QD). A short one dimensional channel, in the form of a quantum point contact (QPC), in close proximity to the QD, serves as a which path detector. We find that by varying the properties of the QPC detector we affect the visibility of the interference, inducing thus dephasing. We develop a simple model to explain the dephasing due to the nearby detector and find good agreement with the experiment.

quant-ph↗

arXiv1997

Direct Observation of a Fractional Charge

We performed measurements of Quantum Shot Noise in order to determine the quasiparticle charge in the Fractional Quantum Hall regime. The noise is generated by a current flow through a partially transmitting Quantum Point Contact in a 2DEG. The noise is directly proportional to the charge of the quasiparticles, thus allowing direct determination of the charge. We measured Quantum Shot Noise at a filling factor of 1/3 and found that the charge is e/3; as predicted by Laughlin.

cond-mat.mes-hall↗

arXiv1997

Observation of the logarithmic dispersion of high frequency edge excitations

We report phase sensitive measurements of microwave propagation through a high mobility two dimensional electron gas subjected to a perpendicular magnetic field. Two types of configurations were used, one that allows all wave vectors q, and one that selects only specific q values. The spectrum of edge excitations was studied over a broad frequency span, which allowed us to observe the logarithmic dispersion of edge magneto-plasmons.

cond-mat↗