Quantum Hall Effect
In 1980 Klaus von Klitzing finds that the Hall resistance of a thin electron layer in a strong magnetic field sits on exact plateaus, h/e² (about 25,813 ohms) divided by a whole number; fractions follow in 1982.
Open in the interactive tree →Von Klitzing measured the steps in silicon transistors at low temperature and received the 1985 Nobel Prize; the quantized resistance is known to better than one part in a billion and serves as a resistance standard. Tsui, Störmer and Gossard found fractional steps in 1982 (Nobel Prize 1998 with Laughlin), and in the same year Thouless and colleagues explained the plateaus as a topological property, an idea honoured by the 2016 Nobel Prize. Topological insulators followed, predicted by Kane and Mele in 2005 and observed in HgTe by Molenkamp's group in 2007.
Prerequisites
- Quantum Mechanics1925Landau levels of electrons in a magnetic field
- Solid-State Physics & Bands1931Electron bands and two-dimensional electron layers in semiconductors
- MOSFET & CMOS (The Chip Switch)1959The electron layer under the gate of a silicon MOSFET
Unlocks
- SI Units Redefined (New Kilogram)2019The ohm is realised with the quantum Hall effect, whose constant h/e² becomes exact once h and e are fixed