Unveiling unconventional magnetism at the surface of Sr$_2$RuO$_4$
Rosalba Fittipaldi, Roman Hartmann, Maria Teresa Mercaldo, Sachio Komori, Anders Bjørlig, Wonshik Kyung, Yuuki Yasui, Takuto Miyoshi, Linde Olde-Olthof, Carla P… 展开作者
Rosalba Fittipaldi, Roman Hartmann, Maria Teresa Mercaldo, Sachio Komori, Anders Bjørlig, Wonshik Kyung, Yuuki Yasui, Takuto Miyoshi, Linde Olde-Olthof, Carla Palomares-Garcia, Veronica Granata, Itai Keren, Wataru Higemoto, Andreas Suter, Thomas Prokscha, Alfonso Romano, Canio Noce, Changyoung Kim, Yoshiteru Maeno, Elke Scheer, Beena Kalisky, Jason W. A. Robinson, Mario Cuoco, Zaher Salman, Antonio Vecchione, Angelo Di Bernardo
Materials with strongly correlated electrons exhibit physical properties that are often difficult to predict as they result from the interactions of large numbers of electrons combined with several quantum degrees of freedom. The layered oxide perovskite Sr$_2$RuO$_4$ is a strongly correlated electron material that has been intensively investigated since its discovery due to its unusual physical properties. Whilst recent experiments have reopened the debate on the exact symmetry of the superconducting state in Sr$_2$RuO$_4$, a deeper understanding of the Sr$_2$RuO$_4$ normal state appears crucial as this is the background in which electron pairing occurs. Here, by using low-energy muon spin spectroscopy we discover the existence of magnetism at the surface of Sr$_2$RuO$_4$ in its normal state. We detect static weak dipolar fields yet manifesting below a relatively high onset temperature larger than 50 K, which reveals the unconventional nature of the observed magnetism. We relate the origin of this phase breaking time reversal symmetry to electronic ordering in the form of orbital loop currents that originate at the reconstructed Sr$_2$RuO$_4$ surface. Our observations set a reference for the discovery of the same magnetic phase in other materials and unveil an electronic ordering mechanism that can influence unconventional electron pairing with broken time reversal symmetry in those materials where the observed magnetic phase coexists with superconductivity.
Disentangling bulk and surface electronic structure using targeted cleave planes in RuO$_2$
Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；SUPA, School of Physics and Astronomy, University of St Andrews（圣安德鲁斯大学物理学与天文学学院（SUPA））；MAX IV Laboratory, Lund University（隆德大学MAX IV实验室）
Unveiling Hidden Magnons with Anomalous Rotational Symmetry
Sejong University（世宗大学）；CNR-SPIN, c/o Università di Salerno（意大利国家研究委员会自旋物理研究所（萨莱诺大学））；Institute of Theoretical Physics, Jagiellonian University（雅盖隆大学理论物理研究所）；International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences（波兰科学院物理研究所磁拓扑国际研究中心）；Center for Correlated Electron Systems, Institute for Basic Science（基础科学研究院相关电子系统中心）；Department of Physics and Astronomy, Seoul National University（首尔大学物理与天文学系）
Unveiling the role of competing fluctuations at an unconventional quantum critical point
量子临界点（QCP）被广泛认为是物质的各种集体量子相的来源。一个中心问题是如何序参量的相位附近的QCP相互作用，并确定驱动量子临界行为的临界动力学的基本特征。对于发生在相关电子系统中的量子临界行为，最有趣的建议之一是，这种行为可能是由序参量的局部（而不是长波长）临界波动引起的。局部临界性被认为会引起能量随温度变化（$E/T$）的动态磁化率与量子临界点（QCP）附近的分数指数缩放。在这里，我们表明，$E/T$缩放确实观察到CeCu $_{6-x}$ Ag $_x$，但仔细检查，波动可以分为两个组成部分，这意味着多个序参量发挥了重要作用，在非常规的临界行为。此外，当对应于磁有序的相图的一面的波动被分离，他们被发现是三维的，并遵守预期的巡游反铁磁QCP附近的长波长波动的标度行为。
Time-reversal symmetry breaking and inherent Josephson diodes in a multi-component order parameter superconductor
University of Cambridge（剑桥大学）；MESA+ Institute for Nanotechnology, University of Twente（特温特大学 MESA+ 纳米技术研究所）；Leiden University（莱顿大学）；Toyota Riken Kyoto University Research Center (TRiKUC)（丰田理研京都大学研究中心 (TRiKUC)）
Directional Andreev-Reflection Signatures of Inter-Orbital Pairing in Sr$_2$RuO$_4$
CNR-SPIN, c/o Università di Salerno（意大利萨莱诺大学CNR-SPIN研究所）；Faculty of Environmental Life, Natural Science and Technology, Okayama University（冈山大学环境生命理工学部）；Department of Applied Physics, Nagoya University（名古屋大学应用物理系）；Max-Planck Institute for Solid State Research（斯图加特马克斯·普朗克固体研究所）；University of St Andrews（圣安德鲁斯大学）；Department of Applied Science and Technology, Politecnico di Torino（都灵理工大学应用科学与技术系）
Quantum Oscillations of $\mathrm{Sr}_2\mathrm{RuO}_4$ under c-Axis Uniaxial Stress
Max Planck Institute for Chemical Physics of Solids（马克斯·普朗克固体化学物理研究所）；Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews（圣安德鲁斯大学物理与天文学学院苏格兰大学物理联盟）；National Institute for Materials Science（国立材料研究所）；Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院量子材料与技术研究所）
Preempting Fermion Sign Problem: Unveiling Quantum Criticality through Nonequilibrium Dynamics in Imaginary Time
School of Physics, Sun Yat-sen University（中山大学物理学院）；Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, Sun Yat-sen University（中山大学磁电物理与器件广东省重点实验室）；Beijing National Laboratory for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所（北京凝聚态物理国家研究中心））；University of Chinese Academy of Sciences（中国科学院大学）
