双层钙钛矿钌氧化物是典型的4d过渡金属氧化物，其电荷、自旋、轨道、晶格等自由度间存在强烈耦合。由于轨道相对于3d电子更为扩展，电子带宽W与库仑势U较为接近，体系位于Mott-Hubbard极限，对外加微扰更为敏感。针对该领域的研究已成为凝聚态物理研究的重点之一，但多重量子序中各种涨落的共存与竞争、多种序参量间的关联和耦合，以及量子序调控背后的物理机制等还有待澄清。本项目将以双层钙钛矿钌氧化物(Sr,Ca)3Ru2O7为研究对象，在现有工作基础上，通过材料设计与压力相结合，对单电子带宽、载流子浓度、晶格畸变等参数进行调制，结合强磁场开展调控，系统研究由此引发的多重量子序间的复杂相变，发掘由此引发的奇异量子物性，探究其自旋涨落和集体激发，阐明各种序参量之间的竞争与制约关系，明晰其背后的物理机制，为深入理解4d过渡金属氧化物中电荷、自旋、轨道、晶格等多种自由度之间相互竞争与合作提供关键实验信息。

Double layered perovskite ruthenate is a typical 4d transition metal oxides (TMOs), in which spin, charge, orbital and lattice degrees of freedom are strongly coupled. Compared to their 3d cousins, orbitals of 4d transition metal oxides (TMOs) are more extended in the space, leading to comparable electron bandwidth U and Coulomb repulsion U and pushing the system close to the Mott-Hubbard limit. This results in unstable ground states and makes the system sensitive to external stimulations such as the magnetic field, pressure or chemical composition, resulting in exceptional rich quantum phenomena. The study in this area has been a focus in comtemporary condensed matter physics. Nevertheless, there are still many questions remain open. The coexistence and competition among various flucutaitons, the coupling between multiple quantum order parameters, and the underlying physics behind the manipulation of quantum orders are still not fully understood. In this project, we choose to investigate the double layered perovskite ruthenates (Sr,Ca)3Ru2O7, on the basis of our previous studies. We plan to tune the single-electron bandwidth, carrier density, and lattice distortion through the combination of material design and the application of external pressure. On this basis, and with the help of the high magneitic field, we plan to systematically invesigated the complex transitions among multiple quantum orders and resulted unusual quantum phenomena. We want to investigate the spin flucutations and collective excitations in the system, clarify the correlation among multiple order parameters, and try to unravel their underlying physics. This project is expected to provide critical experimental information towards the in depth understanding of the cooperation and competition among charge, spin, orbital and lattice degrees of freedom.