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Schematic plot of point-contact conductance as a function of gate voltage. The conductance shows plateaus at multiples of
A quantum point contact (QPC) is a narrow constriction between two wide electrically conducting regions, of a width comparable to the electronic wavelength (nano- to micrometer).[1]
The importance of QPC lies in the fact that they prove quantisation of ballistic conductance in mesoscopic systems. The conductance of a QPC is quantized in units of , the so-called conductance quantum.
Quantum point contacts were first reported in 1988 by a Dutch team from Delft University of Technology and Philips Research[2] and, independently, by a British team from the Cavendish Laboratory.[3] They are based on earlier work by the British group which showed how split gates could be used to convert a two-dimensional electron gas into one-dimension, first in silicon[4] and then in gallium arsenide.[5][6]
This quantisation is reminiscent of the quantisation of the Hall conductance, but is measured in the absence of a magnetic field. The zero-field conductance quantisation and the smooth transition to the quantum Hall effect on applying a magnetic field are essentially consequences of the equipartition of current among an integer number of propagating modes in the constriction.
^H. van Houten & C.W.J. Beenakker (1996). "Quantum point contacts". Physics Today. 49 (7): 22–27. arXiv:cond-mat/0512609. Bibcode:1996PhT....49g..22V. doi:10.1063/1.881503. S2CID 56100437.
^B.J. van Wees; et al. (1988). "Quantized conductance of point contacts in a two-dimensional electron gas". Physical Review Letters. 60 (9): 848–850. Bibcode:1988PhRvL..60..848V. doi:10.1103/PhysRevLett.60.848. hdl:1887/3316. PMID 10038668.
^D.A. Wharam; et al. (1988). "One-dimensional transport and the quantization of the ballistic resistance". J. Phys. C. 21 (8): L209–L214. Bibcode:1988JPhC...21L.209W. doi:10.1088/0022-3719/21/8/002. S2CID 45112904.
^C.C.Dean and M. Pepper (1982). "The transition from two- to one-dimensional electronic transport in narrow silicon accumulation layers". J. Phys. C. 15 (36): L1287–L1297. Bibcode:1982JPhC...15.1287D. doi:10.1088/0022-3719/15/36/005.
^T. J. Thornton; et al. (1986). "One-Dimensional Conduction in the 2D Electron Gas of a GaAs-AlGaAs Heterojunction". Physical Review Letters. 56 (11): 1198–1201. Bibcode:1986PhRvL..56.1198T. doi:10.1103/PhysRevLett.56.1198. PMID 10032595.
^K-F. Berggren; et al. (1986). "Magnetic Depopulation of 1D Subbands in a Narrow 2D Electron Gas in a GaAs:AlGaAs Heterojunction". Physical Review Letters. 57 (14): 1769–1772. Bibcode:1986PhRvL..57.1769B. doi:10.1103/PhysRevLett.57.1769. PMID 10033540.
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