On January 8, 2019, at the annual National Science-Technology Award Ceremony in the Great Hall of the People in Beijing, Prof Qi-kun Xue’s team was granted the first class National Natural Science Award for “Experimental discovery of the quantum anomalous Hall effect”.

    The quantum anomalous Hall effect is a quantum Hall effect that exists even at zero magnetic field. It not only represents a new type of topological quantum effect, but also has the unique advantage in practical applications of the dissipationless quantum Hall edge states in low-energy-consumption electronic devices. It had been extremely difficult to observe the quantum anomalous Hall effect in real materials. Despite numerous theoretical proposals as early as 1988, there was little experimental progress in this direction in the following two decades.

    Starting from 2009, the team led by Prof. Qi-Kun Xue set out a remarkable journey aiming to experimentally realize the quantum anomalous Hall effect. They established the molecular beam epitaxy growth kinetics of Bi2Se3 family topological insulators and obtained ultrathin films with unprecedented quality, achieved accurate engineering of the band structure, in situ tuning of the chemical potential and robust ferromagnetic order, and eventually observed the quantum anomalous Hall effect, for the very first time, in a magnetic topological insulator thin film.

    In the past a few years, their discovery has been unambiguously confirmed by several world class laboratories following the same experimental procedures they invented. The observation of the quantum anomalous Hall effect concluded the 25-year-long search for the zero field quantum Hall effect and the half-century-long debates on whether or not the intrinsic anomalous Hall effect exists. It not only represents a breakthrough in fundamental physics, but also paves the way for novel applications in resistance standard and low-energy-consumption electronics. The quantum anomalous Hall effect is also the basis for constructing other exotic quantum phases such as axion insulator and chiral topological superconductor. The achievement is widely believed to be one of the most important breakthroughs in condensed matter physics in recent decades.