We characterize the low-energy physics of the two-orbital Hubbard model in the orbital-selective Mott phase, in which one band is metallic and the other insulating. Using dynamical mean-field theory with the numerical renormalization group at zero temperature, we show that this phase has a ferromagnetic instability for any nonzero Hund's rule exchange interaction, which can be understood in terms of an effective spin-1 Kondo Hamiltonian. The metallic band therefore behaves as a singular Fermi liquid for which the self-energy has a logarithmic singularity at the Fermi energy.
Site-Selective Mott Transition in a Quasi-One-Dimensional Vanadate V6O13
利用轨道分辨51 V核磁共振谱研究了准一维体系V6 O 13的金属-绝缘体转变的微观机制。我们发现，过渡涉及一个网站选择性d轨道的顺序提升两个VO 6链中的一个的双重轨道简并。另一个链在整个过渡中在单占据的dxy轨道上留下顺磁矩。这两条链分别稳定了基态的轨道辅助自旋Peierls态和反铁磁长程序。择位Mott跃迁可能是反常金属和Mott-Peierls对偶性的一个来源。
The effect of interorbital hopping on the orbital selective Mottness in a two-band correlation system is investigated by using the dynamical mean-field theory with the Lanczos method as impurity solver. We construct the phase diagram of the two-orbital Hubbard model with interorbital hopping ($t_{12})$, where the orbital selective Mott phases (OSMP) show different evolution trends. We find that the negative interorbital hopping ($t_{12}<0$) can enhance the OSMP regime upon tuning the effective bandwidth ratio. On the contrary, for the cases with positive interorbital hopping ($t_{12}>0$), the …
Comment on: "Orbital-selective Mott transitions in the anisotropic two-band Hubbard model at finite temperatures" by C. Knecht, N. Bluemer, and P. G. J. van Dongen, cond-mat/0505106
详细比较了Liebsch [Phys.Rev.B70，165103（2004）]和C. Knecht，N. Bluemer和P.G. J. van Dongen [cond-mat/0505106（提交至Phys. Rev. Lett.）]给出了这两个结果被证明是非常一致的。因此，Knecht等人的主张：“在早期使用QMC和IPT的研究中没有看到第二次转变”和“我们的高精度数据纠正了Liebsch早期的QMC结果”被证明是没有根据的。
Fingerprints of an Exotic Orbital-Selective Mott Phase in the Block Magnetic State of BaFe$_2$Se$_3$ Ladders
铁基梯形BaFe $_2$ Se $_3$的共振非弹性X射线散射（RIXS）实验揭示了块型反铁磁相中与局域轨道（$dd$）激发相关的意想不到的双峰结构。相关的带状和本地化的激发之间的混合字符也被报道。本文利用密度矩阵重整化群方法计算了多轨道Hubbard链的动量分辨电荷和轨道动力学响应函数。值得注意的是，我们的研究结果定性类似于BaFe $_2$ Se $_3$ RIXS数据，同时也捕捉到存在的长程磁序中子散射，$only$时，该模型是在一个异国情调的轨道选择莫特相（OSMP）。在计算中，实验观察到的零动量转移RIXS峰对应于巡回和莫特绝缘轨道之间的激发。我们提供了实验可测试的动量分辨电荷和轨道动力学结构的预测，这可以提供进一步的洞察OSMP制度的BaFe $_2$ Se $_3$。
The recent detailed study of quasi-one-dimensional iron-based ladders, with the $3d$ iron electronic density $n = 6$, has unveiled surprises, such as orbital-selective phases. However, similar studies for $n=6$ iron chains are still rare. Here, a three-orbital electronic Hubbard model was constructed to study the magnetic and electronic properties of the quasi-one-dimensional $n=6$ iron chain Ce$_2$O$_2$FeSe$_2$, with focus on the effect of doping. Specifically, introducing the Hubbard $U$ and Hund $J_{H}$ couplings and studying the model via the density matrix renormalization group, we report…
Moiré super-potentials in two-dimensional materials allow unprecedented control of the ratio between kinetic and interaction energy. By this, they pave the way to study a wide variety of strongly correlated physics under a new light. In particular, the transition metal dichalcogenides (TMDs) are promising candidate "quantum simulators" of the Hubbard model on a triangular lattice. Indeed, Mott and generalized Wigner crystals have been observed in such devices. Here we theoretically propose to extend this model into the multi-orbital regime by focusing on electron doped systems at filling highe…
The heavy fermion state with Kondo-hybridization (KH), usually manifested in f-electron systems with lanthanide or actinide elements, was recently discovered in several 3d transition metal compounds without f-electrons. However, KH has not yet been observed in 4d/5d transition metal compounds, since more extended 4d/5d orbitals do not usually form flat bands that supply localized electrons appropriate for Kondo pairing. Here, we report a doping- and temperature-dependent angle-resolved photoemission study on 4d Ca2-xSrxRuO4, which shows the signature of KH. We observed a spectral weight transf…
Spin dynamics of the block orbital-selective Mott phase
铁基超导体显示出各种各样的磁相，起源于电子、轨道和自旋自由度之间的竞争。以前对一维多轨道哈伯德模型的理论研究揭示了具有块自旋序的轨道选择性Mott相的存在。最近对BaFe $_2$ Se $_3$梯形化合物的非弹性中子散射（INS）实验证实了块OSMP的相关性。此外，粉末INS光谱揭示了一个意想不到的结构，包含低能量的声学和高能量的光学模式。本文用密度矩阵重整化群方法对块体-OSMP体系的动态自旋结构因子进行了理论预测。在协议与实验中，我们发现两个主要特点：低能量色散和高能量dispersionless模式。我们认为，前者代表的块铁磁岛的自旋波的动力学，而后者是由于一种新型的本地现场自旋激发控制的Hund耦合。
The localization-delocalization transition is at the heart of strong correlation physics. Recently, there is great interest in multiorbital systems where this transition can be restricted to certain orbitals, leading to an orbital-selective Mott phase (OSMP). Theoretically, the OSMP is widely studied for kinetically decoupled orbitals, but the effect of interorbital hopping remains unclear. Here, we show how nonlocal interorbital hopping leads to local hybridization in single-site dynamical mean-field theory (DMFT). Under fairly general circumstances, this implies that, at zero temperature, th…
Instability of the Mott or Lieb-Wu insulator caused by an infinitesimal perturbation
利用近藤晶格理论研究了一维哈伯德模型的半满基态。由于近藤效应的存在，任何带隙完全打开的绝缘基态在无限小微扰的存在下都是不稳定的。这一事实对E. H. Lieb和F. Y. Wu，Phys. Rev. Lett. 20，1445（1968），半填充基态是莫特绝缘体。虽然这一说法是基于贝特-安伯解给出的严格结果，但严格结果只是基态是绝缘体的必要条件。
Inspired by the physics of rare earth nickelates, we study the photoemission (PES) and resonant inelastic X-ray scattering (RIXS) spectra of a correlated electron system with two types of insulating sublattices. Sublattice A is characterized by a hybridization gap and a low-spin state, while sublattice B features a Mott gap and a local magnetic moment. We show how the coupling of these two qualitatively different insulating states affects the dynamics of photo-induced charge carriers and how the nonequilibrium states manifest themselves in the PES and RIXS signals. In particular, we find that …
