Thermal ground-state ordering and elementary excitations in artificial magnetic square ice
Thermal ground-state ordering and elementary excitations in artificial magnetic square ice
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DOI：
10.1038/nphys1853
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发表时间：
2011-01-01
期刊：
影响因子：
19.6
通讯作者：
Marrows, Christopher H.
中科院分区：
文献类型：
--
作者：
Morgan, Jason P.;Stein, Aaron;Marrows, Christopher H.
纳米技术的最新进展使人们能够构建模型系统，其中受挫的相互作用可以随意调整，例如人造自旋冰。正方形冰晶格的对称性导致了从众多受挫状态中出现长程有序基态。然而，使用旋转场退磁协议的有效热力学在实验上是非常困难的，因为热平衡的能量势垒非常大。在这里，我们研究了一个非常接近基态的制造样品。在遵循玻尔兹曼定律的频率下，我们将偏离基态的小局域偏离识别为系统的基本激发。因此，我们确定我们观察到的状态是在样品制造过程中发生的真正热力学的冻结残留物。不同激发的相对比例暗示了热化过程中的单极相互作用。
Recent advances in nanotechnology allow model systems to be constructed, in which frustrated interactions can be tuned at will, such as artificial spin ice. The symmetry of the square ice lattice leads to the emergence of a long-range-ordered ground state from the manifold of frustrated states. However, it is experimentally very difficult to access using the effective thermodynamics of rotating-field demagnetization protocols, because the energy barriers to thermal equilibrium are extremely large. Here we study an as-fabricated sample that approaches the ground state very closely. We identify the small localized departures from the ground state as elementary excitations of the system, at frequencies that follow a Boltzmann law. We therefore identify the state we observe as the frozen-in residue of true thermodynamics that occurred during the fabrication of the sample. The relative proportions of different excitations are suggestive of monopole interactions during thermalization.