Scientists of a joint research team in China have proposed a new structurally perfect quantum spin liquids (QSLs) candidate YbMgGaO4 for the first time, which is unique and excellent for future QSL research.
QSLs are novel phases of matter, where quantum spin fluctuations prevent any conventional spin freezing even at 0 K, despite the significant spin-spin interactions. The research on QSL has aroused great interest among researchers in condensed matter physics since the resonating valence bond (RVB) states were proposed by Anderson in 1980s.
The most famous QSL candidates, such as ZnCu3(OH)6Cl2, k-(ET)2Cu2(CN)3, and Yb2Ti2O7, were intensively studied recently. However, some unavoidable structural “shortcomings”, such as magnetic defects, lattice distortions and Dyaloshinskii-Moriya (DM) interactions, make extraction of the intrinsic physics from a real magnet difficult and induce lots of serious research divergence. As a result, the structurally perfect QSL candidates are still highly required so far.
The joint research team found many structural advantages of the new candidate YbMgGaO4 compared to previously reported candidates. It has perfect triangular lattices with R-3m symmetries and the concentration of magnetic defects is negligible (<0.04%). The antisymmetric DM interactions are symmetrically forbidden and the interlayer magnetic interactions are negligible, compared to the intralayer nearest neighboring interactions. High-quality single crystals are available and the nonmagnetic reference single-crystals LuMgGaO4 are available for control experiments, such as extraction of the magnetic heat capacities from the total heat capacities of YbMgGaO4. Further more, the Kramers ground state double is well separated from the first excited double by an energy gap ~ 420 K for Yb3+ ions. It has an odd number of electrons per unit cell and it’s a good insulator. All these factors make YbMgGaO4 ideal for QSL research.
The study was done by Dr. LI Yuesheng and Prof. ZHANG Qingming’s group from Renmin University of China, with the cooperation with Prof. Gang Chen from Fudan University, by using the Electron Spin Resonance spectrometer (ESR), 3He-Magnetic Property Measurement System (MPMS) and low-temperature X-ray Diffractometer (XRD) in the Steady High Magnetic Field Facilities (SHMFF), and dilution refrigerator Physical Property Measurement System (PPMS) in Fudan University.
The above findings were published in Sci. Rep. 5, 16419 (2015) and Phys. Rev. Lett. 115, 167203 (2015).
