Abstract Recently, the latest research results of Professor Liu Hongwu of the State Key Laboratory of Superhard Materials of Jilin University were released. The series of original results obtained by the research institute not only explores the physical mechanism of RDNMR technology which plays an irreplaceable role in the detection of novel quantum states and...
Recently, the latest research results of Professor Liu Hongwu of the State Key Laboratory of Superhard Materials of Jilin University were released. The series of original results obtained by the research institute is not only important for the discussion of the physical mechanism of RDNMR technology which plays an irreplaceable role in novel quantum state detection and its further development, but also opens the edge state chirality in nuclear spin. The door to electronics applications. The project research article "Role of chiral quantum Hall edge states in nuclear spin polarization" was published in "Nature News" on April 20. Associate Professor Yang Kaifeng, the first author of the article, was a teaching assistant in the Department of Physics of Tohoku University in Japan. In 2015, he was introduced as the academic backbone of the State Key Laboratory of Superhard Materials. Corresponding author Liu Hongwu, former associate professor of the Department of Physics of Tohoku University, Japan, visiting professor of the Japan Institute of Physical Property Basics, JST researcher. During the project development, sample growth and device preparation were strongly supported by Professor Santos of the University of Oklahoma and Professor Hirayama of Tohoku University in Japan.
Professor Liu Hongwu's research group first revealed that the edge state chirality plays a crucial role in the nuclear spin polarization process through the ultra-high sensitivity resistive nuclear magnetic resonance (RDNMR) measurement technology. They first successfully implemented RDNMR measurements of the indium telluride quantum well quantum Hall ferromagnetic state (QHF) using the gradient magnetic field method (2016 US invention patent). The method cleverly entangles the chiral edge states into two magnetic domains with similar energies but opposite electron spin polarization, realizing dynamic nuclear polarization (DNP) induced by edge-state scattering. Then, by comparing the RDNMR signals of the Hall strip samples with edge states and the Corbino disc samples with no edge states, the effects of QHF body states and edge states on DNP were designed and designed to eliminate the influence of body state. The unique role of edge state chirality for DNP is demonstrated. In particular, the RDNMR measurement of the current maximum temperature (6K) and the trade-off relationship of the first observed RDNMR signal are realized by using the chiral property, and a new understanding of the abnormal RDNMR dispersion signal mechanism that has been pending in the field is proposed.
In addition, Professor Liu Hongwu and Professor Hawrylak of the University of Ottawa, Canada, proposed a new mechanism for the regulation of nuclear spin polarization using QHF domain wall states, entitled "Manipulation of a nuclear spin by a magnetic domain wall in a quantum Hall ferromagnet". "Environmental Report" in the open source journal of Nature. Professor Liu Hongwu was invited as a member of the conference to participate in the "Spin Dynamics" international conference to be held in South Korea in May and to make a research report.
Background information:
Quantum Hall Effect (QHE)
It was one of the most important physical discoveries of the twentieth century. The field research was awarded the Nobel Prize in Physics twice in 1985 and 1998. In 1982, American physicist David Solis introduced the mathematical concept of topology to QHE for the first time, revealing that its integral multiple conductivity is the intrinsic nature of some materials (he was awarded the 2016 Nobel Prize in Physics). One of the important contributions). Topologically, the phase transitions of different topological states inside and outside the QHE Hall strip sample give the boundary electrons no dissipative flow characteristics.
Chiral edge state
The time-reversed symmetry breaking caused by the external magnetic field blocks the boundary electron backscattering path, so that it can only flow in one direction without dissipating flow and the direction depends on the magnetic field orientation, forming a chiral edge state. The edge-state chirality model has recently contributed directly to the discovery of topological insulators. Because such materials can realize the non-dissipative flow of edge-state electrons under zero magnetic field and have great application value, they have become the hotspot of current condensed matter physics research. So far, the important role of edge state chirality in the electron transport of quantum systems has been widely known.
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