Biffin A, Rüegg Ch, Embs J, Guidi T, Cheptiakov D, Loidl A, Tsurkan V, Coldea R
Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland.
Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
Phys Rev Lett. 2017 Feb 10;118(6):067205. doi: 10.1103/PhysRevLett.118.067205.
The spinel FeSc_{2}S_{4} has been proposed to realize a near-critical spin-orbital singlet (SOS) state, where entangled spin and orbital moments fluctuate in a global singlet state on the verge of spin and orbital order. Here we report powder inelastic neutron scattering measurements that observe the full bandwidth of magnetic excitations and we find that spin-orbital triplon excitations of an SOS state can capture well key aspects of the spectrum in both zero and applied magnetic fields up to 8.5 T. The observed shift of low-energy spectral weight to higher energies upon increasing applied field is naturally explained by the entangled spin-orbital character of the magnetic states, a behavior that is in strong contrast to spin-only singlet ground state systems, where the spin gap decreases upon increasing applied field.
有人提出，尖晶石FeSc₂S₄可实现近临界自旋 - 轨道单重态（SOS），其中纠缠的自旋和轨道矩在自旋和轨道有序的边缘以全局单重态波动。在此，我们报告了粉末非弹性中子散射测量结果，该测量观察到了磁激发的全带宽，并且我们发现，SOS态的自旋 - 轨道三重子激发能够很好地捕捉零磁场和高达8.5 T的外加磁场下光谱的关键特征。随着外加磁场增加，观察到的低能谱权重向更高能量的移动，自然地由磁态的纠缠自旋 - 轨道特性来解释，这种行为与仅自旋单重基态系统形成强烈对比，在仅自旋单重基态系统中，自旋能隙随着外加磁场增加而减小。
