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After the announcement of the award, people were surprised to find that it was actually an experimental physicist in the field of condensed matter physics, and the winner of the highest national science and technology award was called Xue Qikun.
Among physicists on the mainland, very few have won this honor, which is known as the Michelangelo Prize, which shows how amazing Xue Qikun's research achievements are.
In an interview released after winning the award, Xue Qikun told media reporters that his achievements are the achievements of the team he leads, and he is just a person who is fortunate to be selected as a representative.
Solve difficult problems in electronic devices from an experimental perspective.
In 1983, a new phenomenon appeared in the field of Hall effect research, the "anomalous Hall effect", which seems to be the inverse of the normal Hall effect to a certain extent, hence the word "anomalous" in the name.
At room temperature, we have all seen the experimental phenomenon of the Hall effect, through a rod made of conductive material, after the current is applied horizontally into the vertical magnetic field, the internal charge distribution will be generated inside the material, and the potential difference will form a voltage from the surface of both ends of the material, and the current will be vertically stressed to produce a Hall current.
However, the anomalous Hall effect adds a condition to the Hall effect, that is, a very high Hall resistivity occurs when the concentration of the material is very thin.
This sounds ridiculous to the average person, but it does happen in extremely low temperatures.
In a very low temperature environment, the electrons in the material after the energization will be filled according to the energy level theory, basically there will be no electron displacement, the current is very small, and the voltage presented by the material is also very small, which can be basically ignored.
However, when the concentration of the material is sufficiently sparse, even to the extent that the separation between each atom is relatively large, the phenomenon of electron quantum mechanical degeneration will be revealed, as mentioned above, when the electron quantization rejects the electronic displacement of the Earth Hall effect, the voltage cannot be ignored.
The voltage that plays a role is not very large, and when resistivity is measured using only the classical Hall effect formulation, the final resistivity value is much smaller than that obtained by the Zeeman effect.
However, due to the degeneracy of electrons near the surface due to the degeneracy of electrons at different energy levels, the electrons are mutually repelled and aligned, and the electrons in different energy levels are compressed together, the displacement of electrons increases, and the Hall voltage increases.
Therefore, the final Hall resistivity is very similar to that measured in the quantum Hall effect, mainly because the Hall resistivity formula in the quantum Hall effect contains an electron degenerate ability to block the effect.
The quantum anomalous Hall effect was first observed in 2003 by the team led by Xue, which was awarded the second prize of the National Natural Science Award in 2007.
Most of the electronic devices we see in our daily life are made of semiconductor materials, and Hall resistivity is a very important parameter in electronic devices.
The greater the degree of electronic quantization and degeneracy of the material, the smaller the resistivity, the better the conductivity of the electronic device, while the degeneration trend of the material density under the quantum anomalous Hall resistivity is just the opposite.
The energy loss generated by the conduction of electrons in semiconductor devices will eventually be transported to the environment in the form of heat energy, resulting in energy loss, and solving the problem of heat generation of electronic devices is the fundamental problem of the development of electronic devices, and the development of electronic materials is also constantly seeking materials that can improve conduction performance and reduce energy consumption.
Among them, the quantum anomalous Holki effect is a very important material parameter, and electronic device manufacturers will also refer to the degree of electron energy level filling of the quantum anomalous Hall effect when selecting materials.
If the occurrence of the quantum anomalous Hall effect can be proved experimentally, then the research and selection of materials will be greatly facilitated, which is the difficulty of Xue Qikun and his entourage.
At the time when the quantum anomalous Hall effect was discovered, there were already many experiments to study the conductivity of materials at extremely low temperatures, along with the quantum Hall effect, most of which were the results of the conductivity of electrons in the heterostructure of GaAs materials.
However, the materials used to observe the quantum anomalous Hall effect have never been experimentally observed.
The first problem that Xue Qikun and his entourage had to solve was how to prepare quantum anomalous Hall effect materials, and how to control various chemical parameters in the materials through precise experiments.
Therefore, Xue Qikun and his entourage worked hard from many aspects such as material preparation and improvement of experimental equipment, and constantly explored the correct method in the experimental process, and finally achieved the most advanced results in the observation experiment of quantum anomalous Hall effect.
Three major innovations are an extension of this.
The research direction of Xue Qikun's team is experimental physicists in the field of condensed matter physics, and the main task of the team he leads is to design experimental devices and conduct various physical property experiments in the field of condensed matter physics.
After the results of the quantum anomalous Hall effect measurement were announced in 2003, Xue Qikun's team's task also had a clear direction, that is, the observation experiment of the quantum anomalous Hall effect.
However, for experimental physicists in the field of condensed matter physics, the observation of the quantum anomalous Hall effect is also extremely difficult, because until the discovery of the quantum anomalous Hall effect in 2003, no one thought that the quantum anomalous Hall effect would occur in semiconductor heterostructural materials.
In the semiconductor heterostructure, the composition and structure of the material are strictly controlled by artificial, and it is difficult for the materials we can see in nature to accurately schedule various chemical parameters with human hands, so people usually use existing materials to carry out various experimental studies in experiments.
What Xue's team needs to do is to improve the existing GaAs heterostructure experimental device, and prepare quantum anomalous Hall effect materials by coating doped capture centers and regulating material composition in the heterostructure through precise chemical action vacuum evaporation instrument and molecular beam epitaxy process.
However, this process can not be completed only by relying on the hard work of Xue Qikun and his party, and the innovation of experimental methods is the most important.
After the discovery of the quantum anomalous Hall effect in 2003, the researchers first summarized the previous knowledge of semiconductors, and found that the core reason for the occurrence of the anomalous Hall effect is that the material is doped with silver atoms of metal materials, and the dielectric constant of the material continues to change, so that at extremely low temperatures, the interaction between the doping center and the electrons in the material occurs, and the position of the electrons is quantized, and then the quantum anomalous Hall effect occurs.
Therefore, Xue Qikun and his entourage made up their minds to improve the epitaxial technology of semiconductor materials, and tried to prepare the doping center of metallic silver atoms in the material through efficient chemical vacuum evaporation instrument and precise molecular beam epitaxy experimental technology.
However, this step did not go smoothly, because people at that time still did not know anything about the anomalous Hall effect, and there was no clear direction for improving the technology of molecular beam epitaxy experimental devices, so Xue Qikun and his party worked more to find out the experimental method step by step in the case of the fish caught by the blind cat.
Eventually, they found that the doping center was able to form a quantum degenerate state only on the outer shell of the material's Y-atom quantum dots, resulting in holes equivalent to the metallic silver doping center.
Because the formation of Y-atom quantum dots greatly complicates the preparation process of experimental materials, Xue Qikun and his entourage innovated the original molecular beam epitaxy process, and finally found that directly covering Y-atom quantum dots on the material can form a very good quantum anomalous Hall effect phenomenon in the material.
After the preparation of quantum anomalous Hall effect materials, the experimental results will not be very good if the experimental instruments are not improved.
Therefore, Xue Qikun and his entourage improved the control processing technology on the experimental instrument, and finally observed the quantum anomalous Hall effect in the material by using metal aluminum to control the sample by piezoelectric control after the Y atomic quantum dots were covered on the sample.
After the successful observation of the quantum anomalous Hall effect experiment, Xue Qikun's team was completely unwilling to rest and began to try to solve other problems in the quantum anomalous Hall effect experiment.
In the quantum anomalous Hall effect experiment, Xue Qikun and his entourage analyzed the structure of the doped atoms in the material through a large number of experimental data on the basis of observing the quantum anomalous Hall effect, and made conjectures about the electron filling state of the doped atoms.
However, the observations and conjectures given at that time could not systematically provide an experimental basis for the quantum anomalous Hall effect on the one hand, and could not scientifically explain the nature of the quantum anomalous Hall effect on the other hand.
Therefore, the team led by Xue Qikun organized a new round of experimental research, and finally observed the phenomenon of high hole centers in the material by increasing the doping concentration of different chemical atoms in the quantum anomalous Hall effect experiment, so as to have a systematic understanding of the structural knowledge of the quantum anomalous Hall effect.
In the third round of experiments, they improved the temperature control device of the sample, and observed the relaxation of the quantum anomalous Hall effect by pulsing the sample with heat, so as to realize the relaxation knowledge of the doping center of the sample.
The innovation of these three experimental processes has opened up further research in the field of condensed matter physics, and Xue's team has made many research achievements on the basis of the study of the quantum anomalous Hall effect, but the research content of the quantum anomalous Hall effect and their many contributions are not described.
The significance of scientific discovery.
Xue Qikun's research direction is in the field of condensed matter physics, and his work directly leads to the birth of a new branch in the field of condensed matter physics, rather than just opening a door to this new branch.
After the discovery of the quantum anomalous Hall effect, the research in related fields began to move forward rapidly like a fire was ignited, and the research content of the quantum anomalous Hall effect was not only in physics, but also penetrated into chemistry and biology.
At the same time, the discovery of the quantum anomalous Hall effect was found in the comparative analysis with other studies in the field of condensed matter physics at that time, and this phenomenon had nothing to do with the quantum anomalous Hall effect, but was only ignored by people in the study of the electronic properties of materials at that time.
The discovery of the quantum anomalous Hall effect is actually a fortunate thing, otherwise the researchers would have gone to the corner and would have been silent.
Xue Qikun, on the other hand, could apply the research results of the quantum anomalous Hall effect to other research contents at that time, so as to make greater progress in research.
The research content of the quantum anomalous Hall effect has gone far beyond the free electron gas model at that time, and Xue's research results can continue to provide new ideas for other fields of research on this basis.
At the same time, Xue Qikun's experience in optoelectronic experiments during quantum anomalous Hall effect experiments can also help the team led by Xue Qikun to quickly study the content in other fields.
In the subsequent research results of his team, people were able to discover their light from the content of the research