We investigate the electronic structure of SrMnO$_3$ with Density Functional Theory (DFT) plus Dynamical Mean-Field Theory (DMFT). Within this scheme the selection of the correlated subspace and the construction of the corresponding Wannier functions is a crucial step. Due to the crystal field splitting of the Mn-$3d$ orbitals and their separation from the O-2$p$ bands, SrMnO$_3$ is a material where on first sight a 3-band $d$-only model should be sufficient. However, in the present work we demonstrate that the resulting spectrum is considerably influenced by the number of correlated orbitals and the number of bands included in the Wannier function construction. For example, in a $d$-$dp$ model we observe a splitting of the \tg lower Hubbard band into a more complex spectral structure, not observable in $d$-only models. To illustrate these high-frequency differences we employ the recently developed Fork Tensor Product State (FTPS) impurity solver, as it provides the necessary spectral resolution on the real-frequency axis. We find that the spectral structure of a 5-band $d$-$dp$ model is in good agreement with PES and XAS experiments. Our results demonstrate that the FTPS solver is capable of performing full 5-band DMFT calculations directly on the real-frequency axis.
A Kondo semiconductor CeRu$_2$Al$_{10}$ with an orthorhombic crystal structure shows an unusual antiferromagnetic ordering at rather high temperature $T_0$ of 27.3 K, which is lower than the Kondo temperature $T_{\rm K}\sim$ 60 K. In optical conductivity [$σ(ω)$] spectra that directly reflect electronic structure, the $c$-$f$ hybridization gap between the conduction and $4f$ states is observed at around 40 meV along the three principal axes. However, an additional peak at around 20 meV appears only along the $b$ axis. With increasing $x$ to 0.05 in Ce(Ru$_{1-x}$Rh$_x$)$_2$Al$_{10}$, the $T_0$ …
Neural-Network Quantum Embedding Solvers for Correlated Materials
Center for Computational Quantum Physics, Flatiron Institute（平顿研究所计算量子物理中心）；Collège de France（法兰西公学院）；CPHT, CNRS, Ecole Polytechnique, IP Paris（巴黎综合理工学院、法国国家科学研究中心、巴黎高等研究院）；DQMP, Université de Genève（日内瓦大学）；Department of Physics, Columbia University（哥伦比亚大学物理系）；Université Paris-Saclay, CNRS, CEA, Institut de Physique Théorique（巴黎萨克雷大学、法国国家科学研究中心、法国原子能和替代能源委员会、理论物理研究所）
Field-direction sensitivity of Kondo hybridization in UTe$_2$
NIST Center for Neutron Research（美国国家标准与技术研究院中子研究中心）；Department of Physics and Astronomy, University of Maryland（马里兰大学物理与天文系）；Department of Materials Science, University of Maryland, College Park（马里兰大学帕克分校材料科学系）；Neutron Scattering Division, Oak Ridge National Laboratory（橡树岭国家实验室中子散射部）；PSI Center for Neutron and Muon Sciences（瑞士保罗谢勒研究所中子与μ子科学中心）；Physik-Institut, Universität Zürich（苏黎世大学物理学院）
We present a detailed temperature and frequency dependence of the optical conductivity measured on clean high quality single crystals of URu$_{2}$Si$_{2}$ of $ac$- and $ab$-plane surfaces. Our data demonstrate the itinerant character of the narrow 5f bands, becoming progressively coherent as temperature is lowered below a cross-over temperature $T^*{\sim}75~K$. $T^*$ is higher than in previous reports as a result of a different sample preparation, which minimizes residual strain. We furthermore present the density-response (energy-loss) function of this compound, and determine the energies of …
The recent discovery of topological Kondo insulating behaviour in strongly correlated electron systems has generated considerable interest in Kondo insulators both experimentally and theoretically. The Kondo semiconductors CeT2Al10 (T=Fe, Ru and Os) possessing a c-f hybridization gap have received considerable attention recently because of the unexpected high magnetic ordering temperature of CeRu2Al10 (TN=27 K) and CeOs2Al10 (TN=28.5 K) and the Kondo insulating behaviour observed in the valence fluctuating compound CeFe2Al10 with a paramagnetic ground state down to 50 mK. We are investigating …
Optical study of charge instability in CeRu2Al10 in comparison with CeOs2Al10 and CeFe2Al10
利用光学电导谱、Ce 3d X射线光电子能谱和能带计算研究了CeRu $_2$ Al $_{10}$在$T_0$ = 28 K的异常高温下的反铁磁转变的各向异性电子结构.发现$ac$平面的电子结构是近藤半导体的电子结构，而沿b轴的电子结构在32 K以下具有嵌套（略高于$T_0$）。这些特性与CeO_3-$_2$-Al $_{10}$ [S. Kimura { \it等人}，物理修订信函106，056404（2011）.]。CeRu $_2$ Al $_{10}$和CeOs $_2$ Al $_{10}$的导电电子和$4f$电子之间的$c$-$f$杂化强度弱于CeFe $_2$ Al $_{10}$，显示没有磁有序。这些结果表明，沿b轴的一维弱$c$杂化和在$ac$平面的二维强杂化相结合的电子结构引起电荷密度波（CDW）不稳定性，CDW态诱导磁有序.
High magnetic fields induce a pronounced in-plane electronic anisotropy in the tetragonal antiferromagnetic metal CeRhIn$_{5}$ at $H^{*} \gtrsim 30$ T for fields $\simeq 20^{\mathrm{o}}$ off the $c$-axis. Here we investigate the response of the underlying crystal lattice in magnetic fields to $45$ T via high-resolution dilatometry. Within the antiferromagnetic phase of CeRhIn$_{5}$, a finite magnetic field component in the tetragonal $ab$-plane explicitly breaks the tetragonal ($C_{4}$) symmetry of the lattice well below $H^{*}$ revealing a finite nematic susceptibility at low fields. A modest…
Magnon-phonon hybrid excitations are studied theoretically in a two-dimensional antiferromagnet with an easy axis normal to the plane. We show that two magnon bands and one phonon band are intertwined by the magnetoelastic coupling through a nontrivial SU(3) topology, which can be intuitively perceived by identifying a skyrmion structure in the momentum space. We develop a continuum theory as the long-wavelength approximation to the tight-binding model, showing our results are insensitive to lattice details and generally applicable to two-dimensional antiferromagnets. The theoretical results c…
We measured the transverse magnetoresistivity of the mixed valence compound $α$-YbAlB$_4$. Two configurations were used where current was applied along [110] direction for both and magnetic field was applied along [-110] and $c$-axis. We found the transverse magnetoresistivity is highly anisotropic. In the weak field below 1 T, it is consistent with stronger $c$-$f$ hybridization in the $ab$ plane which was suggested from the previous zero field resistivity measurements. At the higher field above 3 T, we observed a negative transverse magnetoresistivity for the field applied along the $c$-axis…
An anisotropic Kondo semiconductor CeOs$_2$Al$_{10}$ exhibits an unusual antiferromagnetic order at rather high transition temperature $T_0$ of 28.5 K. Two possible origins of the magnetic order have been proposed so far, one is the Kondo coupling of the hybridization between the conduction ($c$) and the $4f$ states and the other is the charge-density wave/charge ordering along the orthorhombic $b$ axis. To clarify the origin of the magnetic order, we have investigated the electronic structure of hole- and electron-doped CeOs$_2$Al$_{10}$ [Ce(Os$_{1-y}$Re$_y$)$_2$Al$_{10}$ and Ce(Os$_{1-x}$Ir$…
We present a new impurity solver for dynamical mean-field theory based on imaginary-time evolution of matrix product states. This converges the self-consistency loop on the imaginary-frequency axis and obtains real-frequency information in a final real-time evolution. Relative to computations on the real-frequency axis, required bath sizes are much smaller and less entanglement is generated, so much larger systems can be studied. The power of the method is demonstrated by solutions of a three band model in the single and two-site dynamical mean-field approximation. Technical issues are discuss…
Neural network impurity solver for real-frequency dynamical mean-field theory
Suzhou Institute for Advanced Research, University of Science and Technology of China（中国科学技术大学苏州高等研究院）；School of Artificial Intelligence and Data Science, University of Science and Technology of China（中国科学技术大学人工智能与数据科学学院）；National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University（南京大学固体微结构物理实验室和物理系）；Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学先进微结构协同创新中心）
Field-rigid Ising antiferromagnetism with giant spin-flip fields in Van der Waals UOTe
Washington University in St. Louis（圣路易斯华盛顿大学）；National High Magnetic Field Laboratory, Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室国家高磁场实验室）；Neutron Scattering Division, Oak Ridge National Laboratory（橡树岭国家实验室中子散射部）；Harvard University（哈佛大学）；National High Magnetic Field Laboratory, Florida State University（佛罗里达州立大学国家高磁场实验室）
Directional Manipulation of a Staggered Charge Density Wave and Kondo Resonance in UTe2
University of Notre Dame（圣母大学）；Stavropoulos Center for Complex Quantum Matter, University of Notre Dame（圣母大学斯塔夫罗普洛斯复杂量子物质中心）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）
We describe the use of coupled-cluster theory as an impurity solver in dynamical mean-field theory (DMFT) and its cluster extensions. We present numerical results at the level of coupled-cluster theory with single and double excitations (CCSD) for the density of states and self-energies of cluster impurity problems in the one- and two-dimensional Hubbard models. Comparison to exact diagonalization shows that CCSD produces accurate density of states and self-energies at a variety of values of $U/t$ and filling fractions. However, the low cost allows for the use of many bath sites, which we defi…
