Spin-dynamics in the S= 1/2 trimer chain compound Na2Cu3Ge4O12

Spin-trimer chain systems are of current interest due to unconventional properties arising from the strong quantum fluctuations and topology, such as, quantum phenomenon of magnetization plateau. The compound Na2Cu3Ge4O12 is a model spin-1/2 AFM trimer chain system having a non-collinear AFM ordered ground state below TN = 2.25 K with highly reduced ordered moment ~ 0.3 muB/Cu2+ at 0.25 K. Our recent inelastic neutron scattering measurements on Na2Cu3Ge4O12 using the MERLIN spectrometer down to 2.25 K reveal three discrete energy excitation modes at ~ 2.6, 18.5 and 30 meV, with a weak dispersive excitations below 2.6 meV, suggesting a couple trimer chain model. Here, we propose additional detailed measurements at temperatures below TN = 2.25 K using MERLIN spectrometer which are essential for a complete understanding of the coupled spin-trimer system.

自旋三聚体链系统（Spin-trimer chain systems）目前广受关注，其源于强量子涨落与拓扑结构的非经典物性，例如磁化平台（magnetization plateau）量子现象。化合物Na₂Cu₃Ge₄O₁₂是一款模型自旋-1/2反铁磁（antiferromagnetic, AFM）三聚体链系统，在奈耳温度（Néel temperature, TN）=2.25 K以下呈现非共线反铁磁有序基态，在0.25 K时的有序磁矩被大幅压低至约0.3 μB/Cu²+（玻尔磁子，μB）。我们近期使用MERLIN光谱仪在低至2.25 K的温度下对Na₂Cu₃Ge₄O₁₂开展的非弹性中子散射（inelastic neutron scattering）测量显示，在约2.6 meV、18.5 meV与30 meV处存在三个离散能量激发模式，且在2.6 meV以下存在弱色散激发，这表明该体系符合耦合三聚体链模型。本文提出，需使用MERLIN光谱仪在低于奈耳温度TN=2.25 K的条件下开展额外的精细化测量，这对全面理解该耦合自旋三聚体系统至关重要。