Magnetic excitations in a tuneable S = 1/2 spin ladder system near quantum criticality

Spin ladders are excellent model systems for studying quantum phase transitions, as they exhibit a quantum critical point between non-magnetic spin singlet dimers to Néel magnetic order as inter-ladder exchange is increased. Ba2CuTeO6 is a Cu2+ S = 1/2 two-leg spin ladder system, that is close to the quantum critical point on the Néel ordered side. By replacing Te with W in a Ba2CuTe1-xWxO6 solid solution, we have managed to suppress the magnetic order as indicated by muon spin rotation measurements. We will use inelastic neutron scattering to study magnetic excitations in these doped samples. This will allow us to establish whether we have succeeded in stabilizing a spin singlet ground state and to study quantum criticality near the QCP.

自旋梯子是研究量子相变的理想模型体系，因其在梯间交换作用增强时，会展现出非磁性自旋单态二聚体与奈尔磁有序之间的量子临界点。Ba₂CuTeO₆是Cu²⁺自旋S=1/2的双腿自旋梯子体系，处于奈尔有序侧且靠近量子临界点。通过在Ba₂CuTe₁₋ₓWₓO₆固溶体中用钨（W）取代碲（Te），我们已借助μ子自旋旋转（muon spin rotation）测量证实磁有序被抑制。我们将采用非弹性中子散射（inelastic neutron scattering）技术研究这些掺杂样品中的磁激发，这将使我们能够确定是否成功稳定了自旋单态基态，并探究量子临界点（QCP）附近的量子临界行为。