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标题：Direct bulk-sensitive probe of 5f symmetry in URu2Si2
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作者：Martin Sundermann ; Maurits W. Haverkort ; Stefano Agrestini 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：49
页码：13989-13994
DOI：10.1073/pnas.1612791113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe 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 5[IMG]f1.gif" ALT="Formula" BORDER="0"> 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 [IMG]f1.gif" ALT="Formula" BORDER="0">-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 5[IMG]f1.gif" ALT="Formula" BORDER="0"> ground-state wave function is composed mainly of the [IMG]f2.gif" ALT="Formula" BORDER="0"> with majority [IMG]f3.gif" ALT="Formula" BORDER="0"> = [IMG]f4.gif" ALT="Formula" BORDER="0"> + [IMG]f5.gif" ALT="Formula" BORDER="0"> and/or [IMG]f6.gif" ALT="Formula" BORDER="0"> singlet states. The incomplete dichroism indicates the possibility that quantum states of other irreducible representation are mixed into the ground state.
关键词：strongly correlated electron systems ; X-ray spectroscopy ; crystal-electric field ; heavy fermions ; hidden order