Department of Physics, Tohoku University, Aoba, Sendai 980-8578, Japan.
Department of Physics and Mathematics, Aoyama-Gakuin University, Sagamihara 229-8558, Japan.
Phys Rev Lett. 2013 Feb 15;110(7):077205. doi: 10.1103/PhysRevLett.110.077205.
High degeneracy in ground states leads to the generation of exotic zero-energy modes, a representative example of which is the formation of molecular spin-liquid-like fluctuations in a frustrated magnet. Here we present single-crystal inelastic neutron scattering results for the frustrated magnet MgCr(2)O(4), which show that a common set of finite-energy molecular spin excitation modes is sustained in both the liquid-like phase above magnetic ordering temperature T(N) and an ordered phase with an extremely complex magnetic structure below T(N). Based on this finding, we propose the concept of high degeneracy in excited states, which promotes local resonant elementary excitations. This concept is expected to have ramifications on our understanding of excitations in many complex systems, including not only spin but also atomic liquids, complex order systems, and amorphous systems.
在基态中存在高度简并，导致了奇异零能模式的产生，其中一个代表性的例子是在受挫磁体中形成分子自旋液体样涨落。在这里，我们呈现了受挫磁体 MgCr(2)O(4) 的单晶非弹性中子散射结果，结果表明，在高于磁有序温度 T(N)的液态相和低于 T(N)的具有极其复杂磁结构的有序相中，存在一组共同的有限能分子自旋激发模式。基于这一发现，我们提出了激发态中高度简并的概念，这促进了局域共振元激发。这一概念有望对我们理解许多复杂系统中的激发产生影响，这些系统不仅包括自旋，还包括原子液体、复杂有序系统和非晶态系统。
