We investigate the role of long range ferromagnetic order in the electronic structure of Sr$_{1-x}$Ca$_x$RuO$_3$ using high resolution photoemission spectroscopy. SrRuO$_3$ is a ferromagnetic metal but isostructural, isoelectronic CaRuO$_3$ is an enhanced paramagnet. Surface spectra of CaRuO$_3$ exhibit temperature induced modifications. This is not significant in other compositions. This may be attributed to the structural changes observed in previous studies. Interestingly, the bulk spectra reveal unusual spectral changes exhibiting large decrease in the coherent feature intensity corresponding to only ferromagnetic samples, although the Ru moment is very similar in all the compositions.
A series of epitaxial films were grown across the solid solution Ca(x)Sr(1-x)RuO(3) in order to pinpoint the ferromagnetic to paramagnetic quantum phase transition in this system and to study the evolution of transport and magnetic properties in its vicinity. The ferromagnetic Tc of SrRuO(3) was found to decrease linearly with Ca doping levels up to 70%. Further doping resulted in the abrupt elimination of ferromagnetic order, and the onset of low temperature (< 10K) non-Fermi liquid (NFL) resistivity of the form rho ~ rho(0 + AT^(1.5) for samples with x <= 0.75 <= 1.0. The resistivity exponen…
The ferromagnetic quantum phase transition in the perovskite ruthenate Sr$_{1-x}$Ca$_x$RuO$_3$ is studied by low-temperature magnetization and electrical resistivity measurements on thin films. The films were grown epitaxially on SrTiO$_3$ substrates using metalorganic aerosol deposition and characterized by X-ray diffraction and room temperature scanning tunneling microscopy. High residual resistivity ratios of 29 and 16 for $x=0$ and $x=1$, respectively, prove the high quality of the investigated samples. We observe a continuous suppression of the ferromagnetic Curie temperature from $T_C=16…
We show that the pressure-temperature phase diagram of the Mott insulator Ca$_{2}$RuO$_{4}$ features a metal-insulator transition at 0.5GPa: at 300K from paramagnetic insulator to paramagnetic quasi-two-dimensional metal; at $T \leq$ 12K from antiferromagnetic insulator to ferromagnetic, highly anisotropic, three-dimensional metal. % We compare the metallic state to that of the structurally related p-wave superconductor Sr$_{2}$RuO$_{4}$, and discuss the importance of structural distortions, which are expected to couple strongly to pressure.
We report the synthesis of Ca$_2$RuO$_4$ thin films on NdCaAlO$_{4}$ (110), LaAlO$_3$ (100) and LaSrAlO$_4$ (001) substrates and show that epitaxial strain induces a transition from the Mott-insulating phase of bulk Ca$_2$RuO$_4$ into a metallic phase. Magnetometry and spin-polarized neutron reflectometry reveal a low-temperature, small-moment ferromagnetic state in metallic Ca$_2$RuO$_4$ films.
The microscopic origin of triplet superconductivity in Sr$_2$RuO$_4$ is discussed, paying attention to the role of Coulomb interaction, $U_{pp}$, at the O site. It is shown on the $d$-$p$ model that $U_{pp}$ induces a ferromagnetic exchange interaction between "d-electrons" (molecular orbital with $d_{xy}$-symmetry) at adjacent Ru sites, leading to short-range ferromagnetic correlations and promoting Cooper pairing with ($\sin p_x\pm\ii\sin p_y$)-symmetry on the $γ$-band. The reason why such ferromagnetic correlations work effectively may be traced back to the fact that the level of 4d-electro…
By inelastic neutron scattering, we have analyzed the magnetic correlations in the paramagnetic metallic region of the series Ca(2-x)Sr(x)RuO(4), 0.2<=x<=0.62. We find different contributions that correspond to 2D ferromagnetic fluctuations and to fluctuations at incommensurate wave vectors (0.11,0,0), (0.26,0,0) and (0.3,0.3,0). These components constitute the measured response as function of the Sr-concentration x, of the magnetic field and of the temperature. A generic model is applicable to metallic Ca(2-x)Sr(x)RuO(4) close to the Mott transition, in spite of their strongly varying physica…
The electronic structures of the metallic and insulating phases of Ca(2-x)Sr(x)RuO(4) (0<= x <= 2) are calculated using LDA, LDA+U and Dynamical Mean-Field Approximation methods. For x=0 the ground state is an orbitally non-degenerate antiferromagnetic insulator. For 0.2<x<0.5 we propose a state with partial orbital and spin ordering. For x>0.5 the observed Curie-Weiss paramagnetic metallic state possessing a local moment with the unexpected spin S=1/2 is explained by the localization of only two of the three Ru-4d-orbitals.
The reliable {\it ab-initio} description of strongly correlated materials is a long-sought capability in condensed matter physics. The $GW$+EDMFT method is a promising scheme, which provides a self-consistent description of correlations and screening, and does not require user-provided parameters. In order to test the reliability of this approach we apply it to the experimentally well characterized perovskite compound Ca$_2$RuO$_4$, in which a temperature-dependent structural deformation drives a paramagnetic metal-insulator transition. Our results demonstrate that the nonlocal polarization an…
The importance of electronic correlation effects in the layered perovskite Sr$_2$RuO$_4$ is evidenced. To this end we use state-of-the-art LDA+DMFT (Local Density Approximation + Dynamical Mean-Field Theory) in the basis of Wannier functions to compute spectral functions and the quasiparticle dispersion of Sr$_2$RuO$_4$. The spectra are found to be in good agreement with various spectroscopic experiments. We also calculate the $\textbf{k}$-dependence of the quasiparticle bands and compare the results with new angle resolved photoemission (ARPES) data. Two typical manifestations of strong Coulo…
This Letter uses density functional, dynamical mean field, and Landau-theory methods to elucidate the interplay of electronic and structural energetics in the Mott metal-insulator transition. A Landau-theory free energy is presented that incorporates the electronic energetics, the coupling of the electronic state to local distortions and the coupling of local distortions to long-wavelength strains. The theory is applied to Ca$_2$RuO$_4$. The change in lattice energy across the metal-insulator transition is comparable to the change in electronic energy. Important consequences are a strongly fir…
We present an implementation of the rotationally invariant slave boson technique as an impurity solver for density functional theory plus dynamical mean field theory (DFT+DMFT). Our approach provides explicit relations between quantities in the local correlated subspace treated with DMFT and the Bloch basis used to solve the DFT equations. In particular, we present an expression for the mass enhancement of the quasiparticle states in reciprocal space. We apply the method to the study of the electronic correlations in Sr$_2$RuO$_4$ under anisotropic strain. We find that the spin-orbit coupling …
We present a general methodology that enables the disentanglement of the electronic and lattice contributions to the metal-insulator transition by building an energy landscape from numerical solutions of the equation of state. The methodology works with any electronic structure method that provides electronic expectation values at given atomic positions. Applying the theory to rare-earth perovskite nickelates ($R$NiO$_3$) and Ruddlesden-Popper calcium ruthenates (Ca$_2$RuO$_4$) in bulk, heterostructure and epitaxially strained thin film forms using equation of state results from density functi…
Insulator-to-metal transition in Ca$_{2}$RuO$_{4}$ has drawn keen attention because of its sensitivity to various stimulation and its potential controllability. Here, we report a direct observation of Fermi surface, which emerges upon introducing excess oxygen into an insulating Ca$_{2}$RuO$_{4}$, by using angle-resolved photoemission spectroscopy. Comparison between energy distribution curves shows that the Mott insulating gap is closed by eV-scale spectral-weight transfer with excess oxygen. Momentum-space mapping exhibits two square-shaped sheets of the Fermi surface. One is a hole-like $α$…
We have studied relationship between local lattice disorder, Ru 4$d$ spin-orbit interaction, and global spin/orbital orders of Ca$_{2-x}$Sr$_x$RuO$_4$ in the Sr-rich and Ca-rich regions of its phase diagram by using unrestricted Hartree-Fock calculation on a $8\times8$ RuO$_4$ lattice model. The calculations show that the local elongation of RuO$_6$ octahedron in an antiferromagnetic insulator Ca$_2$RuO$_4$ induces local orbital change with making the Mott gap narrower. On the other hand, local compression of RuO$_6$ octahedron in a paramagnetic metal Sr$_2$RuO$_4$ induces global antiferromagn…
We study the electronic states for Ca_{2-x}Sr_{x}RuO_{4} in $0.5\leq x \leq 2$ within the Gutzwiller approximation (GA) on the basis of the three-orbital Hubbard model for the Ru t_{2g} orbitals. The main effects of the Ca substitution are taken account as the changes of the $dp$ hybridizations between the Ru 4d and O 2p orbitals. Using the numerical minimization of the energy obtained in the GA, we obtain the renormalization factor (RF) of the kinetic energy and total RF, which estimates the inverse of the mass enhancement, for three cases with the effective models of x=2 and 0.5 and a specia…
Here, using density functional theory and density matrix renormalization group methods, we investigate the electronic and magnetic properties of RuOCl$_2$ and OsOCl$_2$ with $d^4$ electronic configurations. Different from a previous study using VOI$_2$ with $d^1$ configuration, these systems with $4d^4$ or $5d^4$ do not exhibit a ferroelectric instability along the $a$-axis. Due to the fully-occupied $d_{xy}$ orbital in RuOCl$_2$ and OsOCl$_2$, the Peierls instability distortion disappears along the $b$-axis, leading to an undistorted I${\rm mmm}$ phase (No. 71). Furthermore, we observe strong…
We measured the temperature dependence of low-frequency Raman spectra in Li$_2$RuO$_3$, and observed multipeak quasielastic scattering in the Ru honeycomb polarizations below and above the magnetostructural transition temperature. We attribute this scattering to the fluctuations of the energy density in the spin system. High-frequency electronic light scattering was observed at 2150 $cm^{-1}$. Its intensity increased significantly below the transition temperature, confirming substantial modification of electronic structure due to removal of degeneracy in $t_{2g}$-manifold of Ru$^{4+}$ ions.
The realistic description of correlated electron systems has taken an important step forward a few years ago as the combination of density functional methods and the dynamical mean-field theory was conceived. This framework allows access to both high and low energy physics and is capable of the description of the specific physics of strongly correlated materials, like the Mott metal-insulator transition. A very important step in the procedure is the interface between the band structure method and the dynamical mean-field theory and its impurity solver. We present a general interface between a …
The layered perovskite Sr$_2$RuO$_4$ is a most intensively studied superconductor, but its pairing mechanism, which is often coupled intimately with magnetic fluctuations in correlated materials, is still an open question. Here we present a systematic evolution of the Seebeck coefficient in Co- and Mn-substituted Sr$_2$RuO$_4$ single crystals, in which ferromagnetic and antiferromagnetic glassy states respectively emerge in proximity to the superconducting phase of the parent compound. We find that the Seebeck coefficient $S$ divided by temperature $T$, $S/T$, shows a maximum near characterist…
We demonstrate that the cluster-glass state emerges as ferromagnetic quantum criticality is avoided in itinerant ferromagnet Sr1-x(La0.5K0.5)xRuO3. In this compound, the ferromagnetic order is suppressed by increasing x, and then disappears at the critical concentration: x=0.5. In this x range, the present study reveals that no prominent feature is ascribed to the quantum critical fluctuations in specific heat. Instead, ac magnetic susceptibility exhibits a broad peak due to spontaneous spin freezing, and the peak temperature depends significantly on the frequency of the applied ac magnetic fi…
We investigate the optical conductivity of Sr$_{1-x}$Ca$_x$RuO$_3$ across the ferromagnetic to paramagnetic transition that occurs at $x=0.8$. The thin films were grown by metalorganic aerosol deposition with $0 \leq x \leq 1$ onto NdGaO$_3$ substrates. We performed THz frequency domain spectroscopy in a frequency range from 3~cm$^{-1}$ to 40~cm$^{-1}$ (100~GHz to 1.4~THz) and at temperatures ranging from 5~K to 300~K, measuring transmittivity and phase shift through the films. From this we obtained real and imaginary parts of the optical conductivity. The end-members, ferromagnetic SrRuO$_3$ …
Using a three-band Hubbard Hamiltonian we calculate within the random-phase-approximation the spin susceptibility, $χ({\bf q},ω)$, and NMR spin-lattice relaxation rate, 1/T$_1$, in the normal state of the triplet superconductor Sr$_2$RuO$_4$ and obtain quantitative agreement with experimental data. Most importantly, we find that due to spin-orbit coupling the out-of-plane component of the spin susceptibility $χ^{zz}$ becomes at low temperatures two times larger than the in-plane one. As a consequence strong incommensurate antiferromagnetic fluctuations of the quasi-one-dimensional $xz$- and $y…
Using a two-dimensional Hubbard Hamiltonian for the three electronic bands crossing the Fermi level in Sr$_2$RuO$_4$ we calculate the band structure and spin susceptibility $χ({\bf q}, ω)$ in quantitative agreement with nuclear magnetic resonance (NMR) and inelastic neutron scattering (INS) experiments. The susceptibility has two peaks at {\bf Q}$_i = (2π/3, 2π/3)$ due to the nesting Fermi surface properties and at {\bf q}$_i = (0.6π, 0)$ due to the tendency towards ferromagnetism. Applying spin-fluctuation exchange theory as in layered cuprates we determine from $χ({\bf q}, ω)$, electronic di…
We investigate the role of electron correlation in the electronic structure of honeycomb lattice Li$_2$RuO$_3$ using photoemission spectroscopy and band structure calculations. Monoclinic Li$_2$RuO$_3$ having Ru network as honeycomb lattice undergoes magneto-structural transition at T$_c$ $\sim$ 540 K from high temperature phase $C2/m$ to low temperature dimerized phase $P2_1/m$. Room temperature valence band photoemission spectra reveal an insulating ground state with no intensity at Fermi level ($E_F$). Ru 4$d$ band extracted from high and low photon energy valence band photoemission spectra…
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）
The synthesis of stoichiometric Sr$_2$RuO$_4$ thin films has been a challenge because of the high volatility of ruthenium oxide precursors, which gives rise to ruthenium vacancies in the films. Ru vacancies greatly affect the transport properties and electronic phase behavior of Sr$_2$RuO$_4$, but their direct detection is difficult due to their atomic dimensions and low concentration. We applied polarized X-ray absorption spectroscopy at the oxygen K-edge and confocal Raman spectroscopy to Sr$_2$RuO$_4$ thin films synthesized under different conditions. The results show that these methods can…
A paradigmatic case of multi-band Mott physics including spin-orbit and Hund's coupling is realised in Ca$_2$RuO$_4$. Progress in understanding the nature of this Mott insulating phase has been impeded by the lack of knowledge about the low-energy electronic structure. Here we provide -- using angle-resolved photoemission electron spectroscopy -- the band structure of the paramagnetic insulating phase of Ca$_2$RuO$_4$ and show how it features several distinct energy scales. Comparison to a simple analysis of atomic multiplets provides a quantitative estimate of the Hund's coupling $J=0.4$ eV. …
We report the evolution of the electronic structure at the surface of the layered perovskite Sr$_2$RuO$_4$ under large in-plane uniaxial compression, leading to anisotropic $B_{1g}$ strains of ${\varepsilon_{xx}-\varepsilon_{yy}=-0.9\pm0.1\%}$. From angle-resolved photoemission, we show how this drives a sequence of Lifshitz transitions, reshaping the low-energy electronic structure and the rich spectrum of van Hove singularities that the surface layer of Sr$_2$RuO$_4$ hosts. From comparison to tight-binding modelling, we find that the strain is accommodated predominantly by bond-length change…
Recently, rutile RuO$_2$ has raised interest for its itinerant antiferromagnetism, crystal Hall effect, and strain-induced superconductivity. Understanding and manipulating these properties demands resolving the electronic structure and the relative roles of the rutile crystal field and $4d$ spin-orbit coupling (SOC). Here, we use O-K and Ru $M_3$ x-ray absorption (XAS) and Ru $M_3$ resonant inelastic x-ray scattering (RIXS) to disentangle the contributions of crystal field, SOC, and electronic correlations in RuO$_2$. The locally orthorhombic site symmetry of the Ru ions introduces significan…
Motivated by the earlier experimental results and \textit{ab initio} studies on the electronic structure of layered ruthenates (Sr$_2$RuO$_4$ and Ca$_2$RuO$_4$) we introduce and investigate the multiband $d-p$ charge transfer model describing a single RuO$_4$ layer, similar to the charge transfer model for a single CuO$_2$ plane including apical oxygen orbitals in high $T_c$ cuprates. The present model takes into account nearest-neighbor anisotropic ruthenium-oxygen $d-p$ and oxygen-oxygen $p-p$ hopping elements, crystal-field splittings and spin-orbit coupling. The intraorbital Coulomb repuls…
Multiconfigurational Analysis of Local Electronic Structure of $\mathrm{RuO_2}$ Using Relativistic Embedded Clusters
St. Petersburg State University（圣彼得堡国立大学）；B. P. Konstantinov Petersburg Nuclear Physics Institute of National Research Center “Kurchatov Institute” (NRC “Kurchatov Institute”–PNPI)（库尔恰托夫国家研究中心B.P.康斯坦丁诺夫圣彼得堡核物理研究所）；St. Petersburg State Technological Institute (Technical University)（圣彼得堡国立技术学院（理工学院））
We investigate the core level spectra of Ca(1-x)Sr(x)RuO(3) employing high resolution photoemission spectroscopy. Sample surface appears to be dominated by the contributions from Ru-O layers. Sr 3p core level spectra are sharp and asymmetric in SrRuO(3) as expected in a metallic system, and exhibit multiple features for the intermediate compositions that can be attributed to the difference in Ca-O and Sr-O covalency. The Ru core level spectra exhibit distinct signature of satellite features due to the finite electron correlations strength among Ru 4d electrons. The intensity of the satellite f…
Sr$_2$MoO$_4$ is isostructural to the unconventional superconductor Sr$_2$RuO$_4$ but with two electrons instead of two holes in the Mo/Ru-t$_{2g}$ orbitals. Both materials are Hund's metals, but while Sr$_2$RuO$_4$ has a van Hove singularity in close proximity to the Fermi surface, the van Hove singularity of Sr$_2$MoO$_4$ is far from the Fermi surface. By using density functional plus dynamical mean-field theory we determine the relative influence of van Hove and Hund's metal physics on the correlation properties. We show that theoretically predicted signatures of Hund's metal physics occur …
We report the evolution of the $k$-space electronic structure of lightly doped bulk Ca$_{2}$RuO$_{4}$ with uniaxial strain. Using ultrathin plate-like crystals, we achieve strain levels up to $-4.1\%$, sufficient to suppress the Mott phase and access the previously unexplored metallic state at low temperature. Angle-resolved photoemission experiments performed while tuning the uniaxial strain reveal that metallicity emerges from a marked redistribution of charge within the Ru $t_{2g}$ shell, accompanied by a sudden collapse of the spectral weight in the lower Hubbard band and the emergence of …
The electric-current stabilized semi-metallic state in the quasi-two-dimensional Mott insulator Ca$_2$RuO$_4$ exhibits an exceptionally strong diamagnetism. Through a comprehensive study using neutron and X-ray diffraction, we show that this non-equilibrium phase assumes a crystal structure distinct from those of equilibrium metallic phases realized in the ruthenates by chemical doping, high pressure and epitaxial strain, which in turn leads to a distinct electronic band structure. Dynamical mean field theory calculations based on the crystallographically refined atomic coordinates and realist…
The chemical and magnetic structures of the series of compounds Ca$_{2-x}$La$_x$RuO$_4$ [$x = 0$, $0.05(1)$, $0.07(1)$, $0.12(1)$] have been investigated using neutron diffraction and resonant elastic x-ray scattering. Upon La doping, the low temperature S-Pbca space group of the parent compound is retained in all insulating samples [$x\leq0.07(1)$], but with significant changes to the atomic positions within the unit cell. These changes can be characterised in terms of the local RuO$_6$ octahedral coordination: with increasing doping the structure, crudely speaking, evolves from an orthorhomb…
The iso-electronic $d^{4}$ compounds of the $4d$ series show rich phase diagrams due to competing spin, charge and orbital degrees of freedom in presence of strong correlations and structural distortions. One such iso-electronic series, $Ca_{2-x}Sr_{x}RuO_{4}$, is studied within the GGA (and spin-orbit coupled GGA) plus DMFT formalism using the hybridization expansion of continuous time Quantum Monte Carlo solver. While the local dynamical correlations make $Sr_{2}RuO_{4}$ a Hund's metal, they drive $Ca_{2}RuO_{4}$ to a Mott insulating ground state. We study the dynamic and static single-parti…
Using quasiparticle self-consistent $GW$ calculations, we re-examined the electronic structure of Sr$_2$RuO$_4$ and SrRuO$_3$. Our calculations show that the correlation effects beyond the conventional LDA (local density approximation) and GGA (generalized gradient approximation) are reasonably well captured by QS$GW$ self-energy without any {\it ad hoc} parameter or any ambiguity related to the double-counting and the downfolding issues. While the spectral weight transfer to the lower and upper Hubbard band is not observed, the noticeable bandwidth reduction and effective mass enhancement are…
Universität Würzburg（维尔茨堡大学）；Würzburg-Dresden Cluster of Excellence ctd.qmat（维尔茨堡-德累斯顿卓越集群 ctd.qmat）；Istituto Officina dei Materiali, CNR-IOM（意大利国家研究委员会材料研究所）
T-square electric resistivity and its thermal counterpart in RuO$_2$
Laboratoire de Physique et d’Etude des Matériaux (CNRS) ESPCI Paris, PSL Université（巴黎高等物理化工学院，巴黎文理研究大学）；Wuhan National High Magnetic Field Center and School of Physics, Huazhong University of Science and Technology（华中科技大学物理学院，武汉国家强磁场中心）；Laboratoire de Cristallographie et Sciences des Matériaux, Université de Caen Normandie, ENSICAEN, CNRS, Normandie Univ, CRISMAT UMR6508（卡昂诺曼底大学）；Nantes Université, CNRS, Institut des Matériaux de Nantes Jean Rouxel (IMN)-UMR 6502（南特大学）
The anomalous Hall effect (AHE) of ferromagnetic thin films of Sr$_{1-x}$Ca$_{x}$RuO$_3$ (0 $\leq x \leq$ 0.4) is studied as a function of $x$ and temperature $T$. As $x$ increases, both the transition temperature $T_c$ and the magnetization $M$ are reduced and vanish near $x \sim$ 0.7. For all compositions, the transverse resistivity $ρ_{H}$ varies non-monotonously with $T$, and even changes sign, thus violating the conventional expression $ρ_{H}=R_o B + 4πR_s M(T)$ ($B$ is the magnetic induction, while $R_o$ and $R_s$ are the ordinary and anomalous Hall coefficients). From the rather complic…
We analyze the spin anisotropy of the magnetic susceptibility of Sr$_2$RuO$4$ in presence of spin-orbit coupling and anisotropic strain using quasi-two-dimensional tight-binding parametrization fitted to the ARPES results. Similar to the previous observations we find the in-plane polarization of the low ${\bf q}$ magnetic fluctuations and the out-of-plane polarization of the incommensurate magnetic fluctuation at the nesting wave vector ${\bf Q}_1 = (2/3 π,2/3 π)$ but also nearly isotropic fluctuations near ${\bf Q}_2=(π/6,π/6)$. Furthermore, one finds that apart from the high-symmetry directi…
Uniaxial pressure applied along an Ru-Ru bond direction induces an elliptical distortion of the largest Fermi surface of Sr$_2$RuO$_4$, eventually causing a Fermi surface topological transition, also known as a Lifshitz transition, into an open Fermi surface. There are various anomalies in low-temperature properties associated with this transition, including maxima in the superconducting critical temperature and in resistivity. In the present paper, we report new measurements, employing new uniaxial stress apparatus and new measurements of the low-temperature elastic moduli, of the strain at w…
The electronic structure of HfZn$_{2}$ has been studied based on the density functional theory within the local-density approximation. The calculation indicates that HfZn$_{2}$ shows ferromagnetic instability. Large enhancement of the static susceptibility over its non-interacting value is found due to a peak in the density of states at the Fermi level.
We have measured soft x-ray photoemission and O 1{\it s} x-ray absorption spectra of Ca$_{1-x}$Sr$_x$RuO$_3$ thin films prepared {\it in situ}. The coherent and incoherent parts have been identified in the bulk component of the photoemission spectra, and spectral weight transfer from the coherent to the incoherent part has been observed with decreasing $x$, namely, with increasing orthorhombic distortion. We propose that, while the Ru 4d one-electron bandwidth does not change with $x$, the distortion and hence the splitting of the $t_{2\text{g}}$ band effectively increases electron correlation…
The solid-solution SrRu$_{1-x}$Rh$_x$O$_3$ ($0\le x \le1$) is a variable-electron-configuration system forming in the nearly-cubic-perovskite basis, ranging from the ferromagnetic 4$d^4$ to the enhanced paramagnetic 4$d^5$. Polycrystalline single-phase samples were obtained over the whole composition range by a high-pressure-heating technique, followed by measurements of magnetic susceptibility, magnetization, specific heat, thermopower, and electrical resistivity. The ferromagnetic order in long range is gradually suppressed by the Rh substitution and vanishes at $x \sim 0.6$. The electronic …
Observation of mirror-odd and mirror-even spin texture in ultrathin epitaxially strained RuO2 films
University of Minnesota-Twin Cities（明尼苏达大学双城分校）；Kyung Hee University（庆熙大学）；Rice University（莱斯大学）；Paul Scherrer Institute（保罗谢勒研究所）；Gwangju Institute of Science and Technology (GIST)（光州科学技术院）
Among unconventional superconductors, Sr$_2$RuO$_4$ has become a benchmark for experimentation and theoretical analysis because its normal-state electronic structure is known with exceptional precision, and because of experimental evidence that its superconductivity has, very unusually, a spontaneous angular momentum, i.e. a chiral state. This hypothesis of chirality is however difficult to reconcile with recent evidence on the spin part of the order parameter. Measurements under uniaxial stress offer an ideal way to test for chirality, because under uniaxial stress the superconducting and chi…
We present an angle resolved photoemission study of the surface and bulk electronic structure of the single layer ruthenate Sr$_2$RuO$_4$. As the early studies of its electronic structure by photoemission and scanning tunneling microscopy were confronted with a problem of surface reconstruction, surface aging was previously proposed as a possible remedy to access the bulk states. Here we suggest an alternative way by demonstrating that, in the case of Sr$_2$RuO$_4$, circularly polarised light can be used to disentangle the signals from the bulk and surface layers, thus opening the possibility …
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）
