（Sr $_{1-x}$ Ca $_x$）$_3$ Ru $_2$ O $_7$（0 $\leq x \leq$ 1）的磁基态是复杂的，从巡回变磁态（0 $\leq x <$ 0.08）到不寻常的重质量近铁磁（FM）态（0.08 $< x <$ 0.4），最后到反铁磁（AFM）态（0.4 $\leq x \leq$ 1）。在这份报告中，我们阐明了这些磁态的电子性质，并表明，在这个系统中的电子和磁性是强耦合的。电子基态从$x =$ 1.0的AFM准二维金属演化到$0.4 \leq x < 1.0$的Anderson局域态（AFM区域）。当磁性状态经历从AFM到近FM状态的转变时，对于$0.25 \leq x < 0.4$，电子基态切换到由磁散射诱导的弱局域态，然后切换到具有面内电阻率$ρ_{ab} \propto T^α$（$α>$ 2）的磁性金属态，对于$0.08 < x < 0.25$。当磁基态进入$x < 0.08$的巡游变磁态时，系统最终转变为费米液体基态。当$x$接近临界组成（$x \sim$ 0.08）时，费米液体温度被抑制到零开尔文，并且观察到非费米液体行为。这些结果表明，在双层双链酸盐的电荷和自旋自由度之间的强烈的相互作用。
英文摘要：
The magnetic ground state of (Sr$_{1-x}$Ca$_x$)$_3$Ru$_2$O$_7$ (0 $\leq x \leq$ 1) is complex, ranging from an itinerant metamagnetic state (0 $\leq x <$ 0.08), to an unusual heavy-mass, nearly ferromagnetic (FM) state (0.08 $< x <$ 0.4), and finally to an antiferromagnetic (AFM) state (0.4 $\leq x \leq$ 1). In this report we elucidate the electronic properties for these magnetic states, and show that the electronic and magnetic properties are strongly coupled in this system. The electronic ground state evolves from an AFM quasi-two-dimensional metal for $x =$ 1.0, to an Anderson localized state for $0.4 \leq x < 1.0$ (the AFM region). When the magnetic state undergoes a transition from the AFM to the nearly FM state, the electronic ground state switches to a weakly localized state induced by magnetic scattering for $0.25 \leq x < 0.4$, and then to a magnetic metallic state with the in-plane resistivity $ρ_{ab} \propto T^α$ ($α>$ 2) for $0.08 < x < 0.25$. The system eventually transforms into a Fermi liquid ground state when the magnetic ground state enters the itinerant metamagnetic state for $x < 0.08$. When $x$ approaches the critical composition ($x \sim$ 0.08), the Fermi liquid temperature is suppressed to zero Kelvin, and non-Fermi liquid behavior is observed. These results demonstrate the strong interplay between charge and spin degrees of freedom in the double layered ruthenates.
Unusual heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio in the double layered ruthenates (Sr$_{1-x}$Ca$_{x}$)$_{3}$Ru$_{2}$O$_{7}$
我们报告了一个不寻常的近铁磁性，重质量态，具有令人惊讶的大威尔逊比$R_{\textrm{w}}$（例如，$R_{\textrm{w}}\sim$ 700，用于$x =$ 0.2）在双层双油酸酯（Sr $_{1-x}$ Ca $_{x}$）中的混合物。这种状态不会演变成一个长程铁磁有序状态，尽管相当强的铁磁关联，但冻结成一个集群自旋玻璃在低温下。此外，观察到的非费米液体行为的证据作为自旋冻结温度的集群自旋玻璃接近零附近的$x \approx$ 0.1。我们讨论了这种独特的磁性状态的起源从费米表面的信息探测霍尔效应测量。
Materials realizing the XY model in two dimensions (2D) are sparse. Here we use neutron triple-axis spectroscopy to investigate the critical static and dynamical magnetic fluctuations in the square-lattice antiferromagnets Ca$_{2}$RuO$_{4}$ and Ca$_{3}$Ru$_2$O$_{7}$. We probe the temperature-dependence of the antiferromagnetic (AFM) Bragg-intensity, the $Q$-width, the amplitude, and the energy-width of the magnetic diffuse scattering in vicinity to the Néel temperature $T_N$ to determine the critical behavior of the magnetic order parameter $M$, correlation length $ξ$, susceptibility $χ$, and …
Anomalous Itinerant-Electron Metamagnetic Transition in the Layered Sr1-xCaxCo2P2 System
本文报道了层状巡游体系Sr $_{1-x}$ Ca $_x$ Co $_2$ P $_2$在高达70 T的磁场中的磁性。对于交换增强的泡利顺磁金属SrCo $_2$ P $_2$，磁化曲线显示两个特征异常。低场异常很小，没有明显的磁滞现象，而高场异常则是巡游电子变磁转变的典型行为。由于自由能的朗道展开，这种磁化曲线的连续转变不能用IEMT的传统唯象理论来解释，而是用具有可区分的两个能态的扩展朗道展开理论来解释。在对Sr $_{1-x}$ Ca $_x$ Co $_2$ P $_2$的系统研究中，随着$x$增加到0.5，变磁跃迁场减小并趋于零，表明在$x \sim 0.5$处存在铁磁量子临界点（QCP）。
Layered ruthenates are a unique class of systems which manifests a variety of electronic and magnetic features emerged from competing energy scales. At the heart of such features lies the multi-orbital physics, especially, the orbital-selective behavior. Here, we propose that the SrRuO3-SrTiO3 heterostructure is a highly tunable platform to obtain the various emergent properties. Employing the density functional theory plus dynamical mean-field theory, we thoroughly investigate the orbital-dependent physics of the system and identify the competing magnetic fluctuations. We show that the epitax…
A new layered perovskite-type oxide Ba$_2$RhO$_4$ was synthesized by a high-pressure technique with the support of convex-hull calculations. The crystal and electronic structure were studied by both experimental and computational tools. Structural refinements for powder x-ray diffraction data showed that Ba$_2$RhO$_4$ crystallizes in a K$_2$NiF$_4$-type structure, isostructural to Sr$_2$RuO$_4$ and Ba$_2$IrO$_4$. Magnetic, resistivity, and specific heat measurements for polycrystalline samples of Ba$_2$RhO$_4$ indicate that the system can be characterized as a correlated metal. Despite the clo…
The ruthenate family of layered perovskites has been a topic of intense interest with much work dedicated to understanding the superconducting state of the single layer, Sr$_2$RuO$_4$. Another longstanding puzzle is the lack of superconductivity in its sister compound, Sr$_3$Ru$_2$O$_7$, which constrains the possible superconducting mechanisms of Sr$_2$RuO$_4$. Here we address a microscopic mechanism that unifies superconducting and spin-density wave order in this family of materials. Beginning from a model of Sr$_2$RuO$_4$ featuring intraband pseudospin-singlet superconductivity originating f…
We report electronic band structure calculations for Sr$_{4}$Ru$_{3}$O$_{10}$ that displays both ferromagnetic and metamagnetic behavior. The density functional calculations find the ground state to be ferromagnetic in agreement with the experiment and we find that the inclusion of Coulomb Hubbard interaction U applied to the Ru 4d states has dramatic effects on the Fermi surface, which reveal the role of Coulomb interactions and correlated many-body physics. The minority spin bands are mainly empty with Fermi surfaces in the outer areas of the Brillouin zone away from the $Γ$ point with bands…
We report the synthesis and characterisation of polycrystalline Na$_2$RuO$_3$, a layered material in which the Ru$^{4+}$ ($4d^4$ configuration) form a honeycomb lattice. The optimal synthesis condition was found to produce a nearly ordered Na$_2$RuO$_3$ ($C2/c$ phase), as assessed from the refinement of the time-of-flight neutron powder diffraction. Magnetic susceptibility measurements reveal a large temperature-independent Pauli paramagnetism ($χ_0 \sim 1.42(2)\times10^{-3}$ emu/mol Oe) with no evidence of magnetic ordering down to 1.5 K, and with an absence of dynamic magnetic correlations, …
The single-layered ruthenate Sr$_2$RuO$_4$ is one of the most enigmatic unconventional superconductors. While for many years it was thought to be the best candidate for a chiral $p$-wave superconducting ground state, desirable for topological quantum computations, recent experiments suggest a singlet state, ruling out the original $p$-wave scenario. The superconductivity as well as the properties of the multi-layered compounds of the ruthenate perovskites are strongly influenced by a van Hove singularity in proximity of the Fermi energy. Tiny structural distortions move the van Hove singularit…
Sr3Ru2O7 belongs to the family of layered strontium ruthenates and exhibits a range of unusual emergent properties, such as electron nematic behavior and metamagnetism. Here, we show that epitaxial film strain significantly modifies these phenomena. In particular, we observe enhanced magnetic interactions and an electron nematic phase that extends to much higher temperatures and over a larger magnetic field range than in bulk single crystals. Furthermore, the films show an unusual anisotropic non-Fermi liquid behavior that is controlled by the direction of the applied magnetic field. At high m…
