Bose-Einstein condensation of the triplet states in the magnetic insulator TlCuCl3
Bose-Einstein condensation of the triplet states in the magnetic insulator TlCuCl3
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DOI：
10.1038/nature01617
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发表时间：
2003-05-01
期刊：
影响因子：
64.8
通讯作者：
Wildes, A
中科院分区：
文献类型：
--
作者：
Rüegg, C;Cavadini, N;Wildes, A
玻色-爱因斯坦凝聚表示具有整数自旋或内禀角动量的全同粒子的集体量子基态的形成。在磁性绝缘体中，磁性是由于具有半整数自旋的未成对壳层电子。然而，在一些这样的化合物（KCuCl 3和TlCuCl 3）中，两个Cu 2+离子反铁磁耦合（1）形成晶体网络中的二聚体：二聚体基态是自旋单线态（总自旋为零），与激发三重态（总自旋为一）分开一个能隙。在这些二聚体化合物中，玻色-爱因斯坦凝聚在理论上是可能的（2）。在临界外磁场下，塞曼分裂三重态分量（玻色子的一种）的能量与基态单线态相交，导致长程磁序;这种跃迁代表了玻色-爱因斯坦凝聚发生的量子临界点。在这里，我们报告的激发光谱在这样一个领域的诱导磁有序状态的实验研究，使用非弹性中子散射测量TlCuCl 3单晶。我们明确地验证了理论预测的（3）三重态玻色-爱因斯坦凝聚的无带隙Goldstone模特性。
Bose-Einstein condensation denotes the formation of a collective quantum ground state of identical particles with integer spin or intrinsic angular momentum. In magnetic insulators, the magnetic properties are due to the unpaired shell electrons that have half-integer spin. However, in some such compounds (KCuCl3 and TlCuCl3), two Cu2+ ions are antiferromagnetically coupled(1) to form a dimer in a crystalline network: the dimer ground state is a spin singlet (total spin zero), separated by an energy gap from the excited triplet state (total spin one). In these dimer compounds, Bose-Einstein condensation becomes theoretically possible(2). At a critical external magnetic field, the energy of one of the Zeeman split triplet components (a type of boson) intersects the ground-state singlet, resulting in long-range magnetic order; this transition represents a quantum critical point at which Bose-Einstein condensation occurs. Here we report an experimental investigation of the excitation spectrum in such a field-induced magnetically ordered state, using inelastic neutron scattering measurements of TlCuCl3 single crystals. We verify unambiguously the theoretically predicted(3) gapless Goldstone mode characteristic of the Bose-Einstein condensation of the triplet states.