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Posted: Apr 11, 2013

First experimental observation of the quantum anomalous Hall effect could revolutionize electronics

(Nanowerk News) Chinese scientists have made the very first experimental observation of a phenomenon known as the quantum anomalous Hall (QAH) effect ("Experimental observation of the quantum anomalous Hall effect in a magnetic topological insulator"), a discovery that will help accelerate the IT revolution and in developing low-power-consumption electronics.
Yang Zhenning, winner of a Nobel Prize in Physics, said at a press conference on Wednesday that the research was ground-breaking in the field, rating it as worthy of a Nobel Prize.
QAH effect is one of the most important physical effects that had remained unobserved worldwide, according to academic Xue Qikun, who has led a team working on the subject since 2008.
Schematic illustration of the quantum anomalous Hall effect
Schematic illustration of the quantum anomalous Hall effect: when the chemical potential is tuned into the energy gap at the Dirac point of a ferromagnetic topological insulator, the zero magnetic field anomalous Hall conductance σxy(0) reaches the quantized value e2/h and forms a plateau, whereas the longitudinal conductance σxx(0) drops to 0.
The discovery, if it is harnessed in the future, will help reduce unnecessary energy consumption stemming from irregular electron collisions, according to Xue.
"The technology may even bring about a supercomputer in the shape of an iPad," predicted Xue.
The QAH effect was predicted to occur in magnetic topological insulators by American scientist Edwin Hall more than 130 years ago. It is a kind of quantum Hall effect realized at zero magnetic field.
The quantum Hall effect describes how a voltage appears at both semiconductor edges when the electrons on a current-carrying semiconductor experience a force while being kept in a magnetic field, Xue explained.
Experimental results showing the quantum anomalous Hall effect
Experimental results showing the quantum anomalous Hall effect: the different curves represent the field dependence of the Hall resistance measured at varied gate voltages. Within a certain range of gate voltages, the zero magnetic field anomalous Hall resistance reaches the quantized value h/e2.
The academic said that although leapfrog development has been made in semiconductor technology, the unsettled problem of thermal dissipation caused by irregular movements of electrons has created a bottleneck for the IT industry's further development.
The research, launched by a team of scientists from Tsinghua University and the Institution of Physics under the Chinese Academy of Science, was conducted on more than 1,000 samples at zero magnetic fields.
However, there remains a long way ahead for the observation to be taken into practical application due to limited research resources at present, Xue added.
Source: Xinhua
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