The concept of quantum spin liquid has attracted the attention of many physicists, not only because of its application prospects, such as high-temperature superconducting mechanism, quantum computing, but also because of the complex and profound physics behind it. After more than forty years of research, people have achieved many theoretical results and proposed a variety of ground states of quantum spin liquids.
Fig.1 Excitation process of spin liquid on a honeycomb lattice with neutrons
The experimental exploration of quantum spin liquid has also achieved some results. In April 2016, researchers from Cambridge and its partner institutions first measured fractionated particles called “Marathon fermions†in a two-dimensional material similar to graphene, and worked well with The Kitaev model fits in. However, the experimental evidence for the existence of the accepted quantum spin liquid is still lacking. On the one hand, the novel material state of quantum spin liquid does not have the symmetry breaking and order parameters corresponding to the traditional phase transition, on the other hand because Many quantum spin liquid candidate materials are unable to grow high-quality large-scale single crystal samples, thus hindering the in-depth study of quantum spin liquids, and the experimental realization of quantum spin liquids is still pending.
After a long period of hard work, the Zhao Jun team of Fudan University successfully developed high-quality, large-scale YbMgGaO4 single crystal samples using the newly built SciDre high temperature and high pressure optical floating zone single crystal furnace in Germany, which allowed in-depth study of the sample. Microscopic properties are possible. Subsequently, the group of Zhao Jun and the team of Chen Gang and his collaborators used the neutron scattering technique to observe the fractional spin excitation----complete spin-excitation spectrum for the first time in the quantum spin liquid candidate YbMgGaO4. The research paper "Evidence for a spinon Fermi surface in a triangular lattice quantum spin liquid candidate" was published online in the journal Nature (DOI: 10.1038/nature 20614) on December 5, 2016.
Figure 2 Sub-spin excitation spectrum measured at a low temperature of 70 mK (covering a large area of ​​the Brillouin zone)
Figure 3 is an excitation spectrum calculated based on the particle-hole excitation of the spin-Fermi surface.
This study is the first to observe the complete spin-excitation spectrum in a two-dimensional triangular lattice system, indicating that the research in the field of quantum spin liquid has taken a big step forward, and it has also injected new research into the research of quantum spin liquid. power. We look forward to Professor Zhao Jun's achievements in the next research work.
About Quantum Design
Quantum Design is the world's leading manufacturer and distributor of scientific equipment, and was founded in 1982 in San Diego, California. The company's SQUID Magnetic Measurement System (MPMS) and Material Integrated Physical Property Measurement System (PPMS) have become the world's recognized top-level measurement platform, widely distributed in the world's most research-oriented fields of materials, physics, chemistry, nanotechnology, etc. laboratory. In 2007, Quantum Design acquired LOT, the largest instrument distributor in Europe, and has become a world-renowned multinational company in the field of scientific instruments. At present, the company has dozens of branches and offices in the United Kingdom, the United States, France, Germany, Brazil, India, Japan and China, and operates in more than 100 countries and regions around the world. China is the most active market for Quantum Design, with offices or offices in Beijing, Shanghai and Guangzhou. Over the past decades, the company's cooperation with China's research and education fields has been fruitful, providing advanced equipment and high-quality services for the advancement of Chinese scientific research.
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