Schlappa J, Schmitt T, Vernay F, Strocov V N, Ilakovac V, Thielemann B, Rønnow H M, Vanishri S, Piazzalunga A, Wang X, Braicovich L, Ghiringhelli G, Marin C, Mesot J, Delley B, Patthey L
Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
Phys Rev Lett. 2009 Jul 24;103(4):047401. doi: 10.1103/PhysRevLett.103.047401. Epub 2009 Jul 21.
We investigate magnetic excitations in the spin-ladder compound Sr_{14}Cu_{24}O_{41} using high-resolution Cu L_{3} edge resonant inelastic x-ray scattering (RIXS). Our findings demonstrate that RIXS couples to two-triplon collective excitations. In contrast to inelastic neutron scattering, the RIXS cross section changes only moderately over the entire Brillouin zone, revealing high sensitivity also at small momentum transfers, allowing determination of the two-triplon energy gap as 100 +/- 30 meV. Our results are backed by calculations within an effective Hubbard model for a finite-size cluster, and confirm that optical selection rules are obeyed for excitations from this spherically symmetric quantum spin-liquid ground state.
我们使用高分辨率Cu L₃边共振非弹性X射线散射（RIXS）研究了自旋梯子化合物Sr₁₄Cu₂₄O₄₁中的磁激发。我们的研究结果表明，RIXS与两个三重子集体激发耦合。与非弹性中子散射不同，RIXS截面在整个布里渊区仅适度变化，在小动量转移时也显示出高灵敏度，从而能够确定两个三重子的能隙为100±30毫电子伏特。我们的结果得到了有限尺寸团簇的有效哈伯德模型内的计算支持，并证实了从这种球对称量子自旋液体基态激发时遵守光学选择规则。
