quantum hall resistance standard

That’s because the universal practical standard for electrical resistance is based on a phenomenon called the quantum Hall effect (QHE), in which resistance takes on perfectly exact, discrete (quantized) values under certain conditions. It is used worldwide to maintain and compare the unit of resistance. 3 Chemical Physics and Explosion Protection, Div. The quantization of the Hall conductance ($${\displaystyle G_{xy}=1/R_{xy}}$$) has the important property of being exceedingly precise. To avoid that this macroscopic electronic state gets destroyed by thermally stimulated scattering processes, a sufficiently low temperature is required. 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The quantum Hall effect is a well-accepted theory in physics describing the behavior of electrons within a magnetic field at extremely low temperatures. The primary standard for resistance is based on the quantum Hall effect (QHE) [ 2] which is presently realized by a lot fewer laboratories [ 3 ]. The quantum Hall effect1 allows the international standard for resistance to be defined in terms of the electron charge and Planck’s constant alone. From the Hall voltage UH and the longitudinal voltage Uxx, the Hall resistance RH and the longitudinal resistance Rxx are calculated according to: Scheme of a GaAs heterostructure with bonded lithographic contacts on a device holder. Vol. The quantum Hall effect provides a universal standard for electrical resistance that is theoretically based on only the Planck constant h and the electron charge e. Currently, this standard is implemented in GaAs/AlGaAs, but graphene's electronic properties have … We demonstrate quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8 K and magnetic fields below 5 … The measurement of standard resistances utilising a standard DC resistance measurement system were also undertaken at the National Metrology Institute of South Africa (NMISA). Metrologia 37, 173–176 (2000) ADS CrossRef Google Scholar The conventional value RK‐90is used to define the quantum Hall resistance value. The SCL quantized Hall resistance standard (QHR) is an instrument that generates SI derived unit of electric resistance based on quantum Hall effect. GaAs heterostructure on a carrier for ac measurements. Si-MOSFET or GaAs-AlGaAs-HEMT devices are used for this purpose. For practical reasons, the quantum Hall resistance usually is used at i = 2. The quantum Hall resistance devices are fabricated based on two-dimensional electron gas formed in GaAs / Al x Ga 1 − x as heterostructures. The quantum Hall effect (QHE) is a quantisation of resistance, exhibited by two-dimensional electronic systems, that is defined by the electron charge e and Planck’s constant h. Those values can be measured to an accuracy of about 1 part per billion. This is named after Klaus von Klitzing, the discoverer of exact quantization. When QHE was first observed in graphene ten years ago, the inherently 2D material became a prime candidate for realizing the quantized Hall resistance (QHR) standard because QHE plateaus could be observed in graphene at lower magnetic field strength and higher temperature than in semiconductor devices. The quantum Hall effect also provides an extremely precise independent determination of the fine-structure constant, a quantity of fundamental importance in quantum electrodynamics. 7 Temperature and Synchrotron Radiation, Div. Every energy level corresponds to a plateau i of the Hall resistance. Current advances: The fine-structure constant and quantum Hall effect . The quantum Hall effect (QHE) provides an invariant reference for resistance linked to natural constants. Under these conditions, the above mentioned equation for the Hall resistance applies: Since the quantum Hall effect occurs only at low temperatures and in strong magnetic fields, a corresponding cryogenic system and a superconducting solenoid are required. GaAs heterostructures became the established material because at a temperature below 1.5 K and in a magnetic field of typically 10 T it yields a precise and robust quantum Hall effect. 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