Fogh Ellen, Nayak Mithilesh, Prokhnenko Oleksandr, Bartkowiak Maciej, Munakata Koji, Soh Jian-Rui, Turrini Alexandra A, Zayed Mohamed E, Pomjakushina Ekaterina, Kageyama Hiroshi, Nojiri Hiroyuki, Kakurai Kazuhisa, Normand Bruce, Mila Frédéric, Rønnow Henrik M
Laboratory for Quantum Magnetism, Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland.
Nat Commun. 2024 Jan 10;15(1):442. doi: 10.1038/s41467-023-44115-z.
In quantum magnetic materials, ordered phases induced by an applied magnetic field can be described as the Bose-Einstein condensation (BEC) of magnon excitations. In the strongly frustrated system SrCu(BO), no clear magnon BEC could be observed, pointing to an alternative mechanism, but the high fields required to probe this physics have remained a barrier to detailed investigation. Here we exploit the first purpose-built high-field neutron scattering facility to measure the spin excitations of SrCu(BO) up to 25.9 T and use cylinder matrix-product-states (MPS) calculations to reproduce the experimental spectra with high accuracy. Multiple unconventional features point to a condensation of S = 2 bound states into a spin-nematic phase, including the gradients of the one-magnon branches and the persistence of a one-magnon spin gap. This gap reflects a direct analogy with superconductivity, suggesting that the spin-nematic phase in SrCu(BO) is best understood as a condensate of bosonic Cooper pairs.
在量子磁性材料中，由外加磁场诱导的有序相可被描述为磁振子激发的玻色 - 爱因斯坦凝聚（BEC）。在强阻挫体系SrCu(BO)中，未观察到清晰的磁振子BEC，这指向了一种替代机制，但探测该物理现象所需的高场一直是详细研究的障碍。在此，我们利用首个专门建造的高场中子散射设施，测量了高达25.9 T的SrCu(BO)的自旋激发，并使用圆柱矩阵乘积态（MPS）计算以高精度重现实验光谱。多个非常规特征表明S = 2束缚态凝聚成了一个自旋向列相，包括单磁振子分支的梯度和单磁振子自旋能隙的持续性。这个能隙反映了与超导的直接类比，表明SrCu(BO)中的自旋向列相最好被理解为玻色子库珀对的凝聚态。
