Quantum spin liquids (QSLs) are novel phases of frustrated spin systems: "Despite the strong magnetic couplings, the strong quantum fluctuations of the systems prevent any spontaneous symmetry breaking even at zero absolute temperature." QSLs can possess lots of novel properties, such as intrinsic topological ordering and fractionalized spin excitations, and had completely capture the great interest of the modern condensed matter physics in recent decades.

However, a perfect QSL candidate material is still absent. Most of the existing candidates are suffering from a lot of structural shortcomings, such as magnetic defects, Dzyaloshinskii-Moriya（DM）interactions, and lattice distortions. These shortcomings hinder the further explorations, and make extracting the intrinsic physics from a real material difficult. Recently, a breakthrough had been made by Dr. Yuesheng Li and Prof. Qingming Zhang from Remin University of China, with the cooperation of Institute of Physics Chinese Academy of Sciences, Fudan University (Prof. Shiyan Li 's group), High Magnetic Field Laboratory Chinese Academy of Sciences, Institute of Solid State Physics Chinese Academy of Sciences, Wuhan National High Magnetic Field Center, and Institute of High Energy Physics Chinese Academy of Science. They first successfully proposed a complete new and structurally perfect QSL candidate material, YbMgGaO₄, without the above structural shortcomings. This work was published on 10 November 2015 in Scientific Reports.

They first experimentally and clearly confirmed a gapless and magnetically disordered  ground state of YbMgGaO₄ almost without residual spin entropy (< 0.6 %) at 60 mK, despite the significant antiferromagnetic couplings (~ 4 K) (the first requirement of QSLs), and aroused the great attention of international counterparts. The single crystal work was published in Yuesheng Li etc, Phys. Rev. Lett. 115, 167203 (2015). Other further experimental works also have been planned to deeply research its novel spin excitations and spin dynamics at extremely low temperatures.

The exact crystal structure of YbMgGaO₄ and LuMgGaO₄ powders were first refined using the synchrotron X-ray radiation diffraction data, obtained from the diffraction station (4B9A) of the Beijing Synchrotron Radiation Facility (BSRF).

paper link：http://www.nature.com/articles/srep16419