Quantum anomalous Hall effect (QAHE) is the "quantum" version of the
anomalous Hall effect. While the anomalous Hall effect requires a combination of magnetic polarization and
spin-orbit coupling to generate a finite Hall voltage even in the absence of an external magnetic field (hence called "anomalous"), the quantum anomalous Hall effect is its quantized version. The Hall conductivity acquires quantized values proportional to integer multiples of the von Klitzing constant (
) (also called
conductance quantum
The conductance quantum, denoted by the symbol , is the quantized unit of electrical conductance. It is defined by the elementary charge
The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalent ...
). In this respect the QAHE is similar to the
quantum Hall effect
The quantum Hall effect (or integer quantum Hall effect) is a quantized version of the Hall effect which is observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall resistance exhib ...
. The integer here is equal to the
Chern number
In mathematics, in particular in algebraic topology, differential geometry and algebraic geometry, the Chern classes are characteristic classes associated with complex vector bundles. They have since found applications in physics, Calabi–Yau ...
which arises out of topological properties of the material
band structure
In solid-state physics, the electronic band structure (or simply band structure) of a solid describes the range of energy levels that electrons may have within it, as well as the ranges of energy that they may not have (called ''band gaps'' or ...
. These effects are observed in systems called quantum anomalous Hall insulators (also called Chern insulators).
The effect was observed experimentally for the first time in 2013 by a team led by
Xue Qikun
Xue Qikun (; born December 1963) is a Chinese physicist. He is a professor of Tsinghua University, Beijing. He has done much work in Condensed Matter Physics, especially on superconductors and topological insulators. In 2013, Xue was the first t ...
at
Tsinghua University
Tsinghua University (; abbr. THU) is a national public research university in Beijing, China. The university is funded by the Ministry of Education.
The university is a member of the C9 League, Double First Class University Plan, Projec ...
.
See also
*
Quantum Hall effect
The quantum Hall effect (or integer quantum Hall effect) is a quantized version of the Hall effect which is observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall resistance exhib ...
*
Hall effect
The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor that is transverse to an electric current in the conductor and to an applied magnetic field perpendicular to the current. It was disc ...
References
Hall effect
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