Direct bulk-sensitive probe of 5f symmetry in URu2Si2
Direct bulk-sensitive probe of 5f symmetry in URu2Si2
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DOI：
10.1073/pnas.1612791113
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发表时间：
2016-08
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通讯作者：
M. Sundermann;M. Haverkort;S. Agrestini;A. Al-Zein;M. Moretti Sala;Y. Huang;M. Golden;A. de Visser;P. Thalmeier;L. Tjeng;A. Severing
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作者：
M. Sundermann;M. Haverkort;S. Agrestini;A. Al-Zein;M. Moretti Sala;Y. Huang;M. Golden;A. de Visser;P. Thalmeier;L. Tjeng;A. Severing
意义在强关联电子材料领域，URU2Si2中的隐藏有序问题是一个尚未得到解答的问题。虽然已经研究了几十年，但对于这一新阶段是如何形成的，仍然没有达成共识。理解隐藏有序相的形成不仅是一个智力问题，也将为设计具有新的奇异性质的量子材料提供新的概念。许多隐序情形都是基于某些基态对称性的假设，本研究针对这一方面进行了研究。通过使用高亮度同步加速器，一种名为非共振非弹性X射线散射的光谱技术使我们能够在体敏感实验中直接测量URu2Si2中5f基态波函数的对称性。尽管经过了30年的研究，URu2Si2中的二级相变为隐藏的有序相伴随着一个仍然是谜的序参数。然而，可以理解，序参数的对称性必须与低位局域电子f态的对称性有关。在这里，我们介绍了一种光谱技术的结果，即芯级非共振非弹性X射线散射(NIXS)。这种方法允许测量局部高多极激发，并且是体敏的。观测到的散射函数的各向异性明确地表明，5f基态波函数主要由Γ1组成，其中大部分JZ=|4⟩+|−4⟩和/或Γ2单重态。不完全二向色性表明，其他不可约表示的量子态可能混合到基态中。
Significance The hidden order problem in URu2Si2 is an unanswered question in the field of strongly correlated electron materials. Although it has been studied for several decades, there is still no consensus about how this new phase forms. Understanding the hidden order phase formation is not only an intellectual problem, it will also advance concepts for designing quantum materials with new exotic properties. Many hidden order scenarios are based on the assumption of certain ground-state symmetries and the present study addresses this aspect. A spectroscopic technique, nonresonant inelastic X-ray scattering, that has become available through the use of high-brilliance synchrotrons, allows us to measure directly in a bulk-sensitive experiment the symmetry of the 5f ground-state wave function in URu2Si2. The second-order phase transition into a hidden order phase in URu2Si2 goes along with an order parameter that is still a mystery, despite 30 years of research. However, it is understood that the symmetry of the order parameter must be related to the symmetry of the low-lying local electronic f-states. Here, we present results of a spectroscopic technique, namely core-level nonresonant inelastic X-ray scattering (NIXS). This method allows for the measurement of local high-multipole excitations and is bulk-sensitive. The observed anisotropy of the scattering function unambiguously shows that the 5f ground-state wave function is composed mainly of the Γ1 with majority Jz = |4⟩ + |−4⟩ and/or Γ2 singlet states. The incomplete dichroism indicates the possibility that quantum states of other irreducible representation are mixed into the ground state.