Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany.; Scottish Universities Physics Alliance, School of Physics and Astronomy, North Haugh, University of St Andrews, St Andrews KY16 9SS, U.K.
Scottish Universities Physics Alliance, School of Physics and Astronomy, North Haugh, University of St Andrews, St Andrews KY16 9SS, U.K.; Max Planck Institute for Solid State Physics, Heisenbergstraße 1, 70569 Stuttgart, Germany.
Sci Adv. 2017 Feb 3;3(2):e1501804. doi: 10.1126/sciadv.1501804. eCollection 2017 Feb.
A major area of interest in condensed matter physics is the way electrons in correlated electron materials can self-organize into ordered states, and a particularly intriguing possibility is that they spontaneously choose a preferred direction of conduction. The correlated electron metal SrRuO has an anomalous phase at low temperatures that features strong susceptibility toward anisotropic transport. This susceptibility has been thought to indicate a spontaneous anisotropy, that is, electronic order that spontaneously breaks the point-group symmetry of the lattice, allowing weak external stimuli to select the orientation of the anisotropy. We investigate further by studying the response of SrRuO in the region of phase formation to two fields that lift the native tetragonal symmetry of the lattice: in-plane magnetic field and orthorhombic lattice distortion through uniaxial pressure. The response to uniaxial pressure is surprisingly strong: Compressing the lattice by ~0.1% induces an approximately 100% transport anisotropy. However, neither the in-plane field nor the pressure phase diagrams are qualitatively consistent with spontaneous symmetry reduction. Instead, both are consistent with a multicomponent order parameter that is likely to preserve the point-group symmetry of the lattice, but is highly susceptible to perturbation.
凝聚态物理的一个主要研究领域是关联电子材料中电子如何自我组织成有序状态，其中一个特别有趣的可能性是它们自发选择一个优先的传导方向。相关电子金属 SrRuO 在低温下具有异常相，表现出对各向异性输运的强烈敏感性。这种敏感性被认为表明存在自发各向异性，即电子有序自发打破晶格的点群对称性，从而允许较弱的外部刺激选择各向异性的方向。我们通过研究 SrRuO 在相变区域对两个场的响应来进一步研究，这两个场提升了晶格的本征四方对称性：面内磁场和通过单轴压力的正交晶格变形。对单轴压力的响应惊人地强烈：通过将晶格压缩约 0.1%，诱导约 100%的输运各向异性。然而，面内场和压力相图都与自发对称降低没有定性一致性。相反，两者都与可能保持晶格点群对称性的多分量有序参数一致，但对扰动非常敏感。
