The standard view is that at low energies Mott insulators exhibit only magnetic properties while charge degrees of freedom are frozen out as the electrons become localized by a strong Coulomb repulsion. We demonstrate that this is in general not true: for certain spin textures {\it spontaneous circular electric currents} or {\it nonuniform charge distribution} exist in the ground state of Mott insulators. In addition, low-energy ``magnetic'' states contribute comparably to the dielectric and magnetic functions $ε_{ik}(ω)$ and $μ_{ik}(ω)$ leading to interesting phenomena such as rotation the electric field polarization and resonances which may be common for both functions producing a negative refraction index in a window of frequencies.
We study the interplay of strong electron correlations and intra-triangle spin exchange at two-thirds filling of the single-orbital Hubbard model on the decorated honeycomb lattice using rotationally invariant slave bosons. We find that the spin exchange tunes between a spin-$1$ Mott insulator, a metal, and a spin-$0$ Mott insulator when the exchange is antiferromagnetic. The Mott insulators occur from effective intra-triangle multi-orbital interactions and are adiabatically connected to the ground state of an isolated triangle. An antiferromagnetic spin exchange, as determined by the Goodenou…
We provide the first unbiased evidence for a higher-order topological Mott insulator in three dimensions by numerically exact quantum Monte Carlo simulations. This insulating phase is adiabatically connected to a third-order topological insulator in the noninteracting limit, which features gapless modes around the corners of the pyrochlore lattice and is characterized by a $\mathbb{Z}_{4}$ spin-Berry phase. The difference between the correlated and non-correlated topological phases is that in the former phase the gapless corner modes emerge only in spin excitations being Mott-like. We also sho…
We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped Ca$_3$Ru$_2$O$_7$. Such an insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings have important implications because a magnetic field usually stabilizes the insulating ground state in a Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of Mott systems with magnetic and electronic instabilities and spin-lattic…
The Mott insulator is the quintessential strongly correlated electronic state. We obtain complete insight into the physics of the two-dimensional Mott insulator by extending the slave-fermion (holon-doublon) description to finite temperatures. We first benchmark its predictions against state-of-the-art quantum Monte Carlo simulations, demonstrating quantitative agreement. Qualitatively, the short-ranged spin fluctuations both induce holon-doublon bound states and renormalize the charge sector to form the Hubbard bands. The Mott gap is understood as the charge gap renormalized downwards by thes…
We study the topological properties of Bose-Mott insulators in one-dimensional non-Hermitian superlattices, which may serve as effective Hamiltonians for cold atomic optical systems with either two-body loss or one-body loss. We find that in the strongly repulsive limit, the Mott insulator states of the Bose-Hubbard model with a finite two-body loss under integer fillings are topological insulators characterized by a finite charge gap, nonzero integer Chern numbers, and nontrivial edge modes in a low-energy excitation spectrum under an open boundary condition. The two-body loss suppressed by t…
Cluster Mott insulators and two Curie-Weiss regimes on an anisotropic Kagome lattice
受量子自旋液体候选材料LiZn 2 Mo 3 O 8最近实验的启发，我们研究了各向异性Kagome晶格上1/6电子填充的单带扩展哈伯德模型.由于晶格的部分填充，需要产生莫特绝缘体，其中电子被定位在簇中，而不是在晶格位置处的位置间排斥相互作用。结果表明，这些团簇莫特绝缘体一般是具有自旋费米面的U（1）量子自旋液体.团簇莫特绝缘体中的电荷激发的性质与传统的莫特绝缘体有很大的不同，我们发现存在一种新颖的团簇莫特绝缘体，其中六角团簇周围的电荷波动诱导了元胞电荷序（PCO）。由于PCO的存在，自旋液体团簇莫特绝缘体中的自旋子激发谱被重构，只有1/3的自旋子激发是磁激活的。基于这些结果，我们提出LiZn_2 Mo_3 O_8中自旋磁化率的两个Curie-Weiss区域可以用具有PCO的团簇莫特绝缘体的有限温度性质以及自旋子的分数激发来解释。现有的和可能的未来实验LiZn 2 Mo 3 O 8，和其他钼基团簇磁体进行了讨论，根据这些理论预测。
Spin susceptibility anomaly in cluster Mott insulators on a partially-filled anisotropic Kagome lattice: applications to LiZn2Mo3O8
受量子自旋液体候选材料LiZn 2 Mo 3 O 8最近实验的启发，我们研究了各向异性Kagome晶格上1/6电子填充的单带扩展哈伯德模型.由于晶格的部分填充，需要产生莫特绝缘体，其中电子被定位在簇中，而不是在晶格位置处的位置间排斥相互作用。我们提供了这样的集群莫特绝缘体的例子，并研究金属态和集群莫特绝缘体的各向异性的可果美晶格之间的相变。结果表明，这些团簇莫特绝缘体一般是具有自旋费米面的U（1）量子自旋液体.然而，在不同的集群莫特绝缘体的电荷激发的性质可能是完全不同的，我们表明，存在一种新的集群莫特绝缘体的电荷波动周围的六边形集群诱导的元胞电荷秩序（PCO）。由于PCO的存在，自旋液体团簇莫特绝缘体中的自旋子激发谱被重构，只有1/3的自旋子激发是磁激活的。同一模型的强耦合极限也通过一个Kugel-Khomskii-like模型进行了分析。基于这些结果，我们认为LiZn_2Mo_3O_8有限温度自旋磁化率的反常行为可以用具有PCO的团簇莫特绝缘体的有限温度性质以及自旋子的分形激发来解释.现有的和可能的未来实验LiZn 2 Mo 3 O 8，和其他钼基团簇磁体进行了讨论，根据这些理论预测。
Ultrafast laser pulses can redistribute charges in Mott insulators on extremely short time scales, leading to the fast generation of photocarriers. It has recently been demonstrated that these photocarriers can form a novel $η$--paired condensate at low temperatures, featuring a staggered superconducting pairing field. In this conference paper, we discuss the origin of the $η$--paired hidden phase and its optical response which may be detected in a pump-probe experiment. The hidden phase may be relevant for possible light-induced superconductivity in Mott insulators.
Motivated by recent progress in the realization of artificial gauge fields and $SU(N)$ Mott insulators using alkaline-earth-like atoms in optical lattices, we develop an unbiased $SU(N)$ real-space dynamical mean-field theory (DMFT) approach to study the effect of spin-orbit coupling and onsite Hubbard interaction $U$ on $SU(3)$ fermionic systems. We investigate the behavior of the local magnetization, double occupancies, and the triple occupancy versus the Hubbard interaction across the metal to Mott insulator transition. We map out the magnetic phase diagram in the large-$U$ limit and show t…
We propose a phenomenological understanding of the recently discovered weak Mott insulator in the moiré superlattice of twisted bilayer graphene, especially the emergent superconductivity at low temperature within the weak Mott insulator phase, namely while lowering temperature, the longitudinal resistivity first grows below temperature $T_m$, but then rapidly drops to zero at even lower temperature $T_c$. An emergent superconductor in an insulator phase is very unusual. Here we propose that this phenomenon is due to the pure two-dimensional nature of the bilayer graphene moiré superlattice. W…
"Nonmagnetic" Dimer Mott insulator induced by the coupling of spin with quantum electric dipoles
基于强耦合分析，提出了一个有效的偶极自旋模型，该模型可以解释“自旋液体莫特绝缘体“的可能起源。这个问题与二聚体莫特绝缘体有关，它使人联想到有机三角晶格系统$κ$ Cu $_2$（CN）$_3$，它的无隙自旋液态已经在二聚体轨道上自旋之间交换耦合的几何阻挫（$J$）的背景下讨论过。事实证明，绝缘体中的另一个自由度，二聚体上的{ \it量子电偶极子}，通过库仑相互作用彼此相互作用，并通过偶极-自旋耦合带来对$J$的显著抑制。
To study excitonic effects on high-harmonic generation (HHG) in Mott insulators, we investigate pumped nonequilibrium dynamics in the one-dimensional extended Hubbard model. By employing time-dependent calculations based on the exact diagonalization and infinite time-evolving block decimation methods, we find the strong enhancement of the HHG intensity around the exciton energy. The subcycle analysis in the sub-Mott-gap regime shows that the intensity region of the time-resolved spectrum around the exciton energy splits into two levels and oscillates following the driving electric field. This …
Electrons undergoing a Mott transition may shed their charge but persist as neutral excitations of a quantum spin liquid (QSL). We introduce concrete two-dimensional models exhibiting this exotic behavior as they transition from superconducting or topological phases into fully charge-localized insulators. We study these Mott transitions and the confinement of neutral fermions at a second transition into a symmetry-broken phase. In the process, we also derive coupled-wire parent Hamiltonians for a non-Abelian QSL and a $\mathbb{Z}_4$ QSL.
The Mott insulating phase of the parent compounds is frequently taken as starting point for the underdoped high-$T_c$ cuprate superconductors. In particular, the pseudogap state is often considered as deriving from the Mott insulator. In this work, we systematically investigate different weakly-doped Mott insulators on the square and triangular lattice to clarify the relationship between the pseudogap and Mottness. We show that doping a two-dimensional Mott insulator does not necessarily lead to a pseudogap phase. Despite its inherent strong-coupling nature, we find that the existence or absen…
We investigate a model for a Mott insulator in presence of a time-periodic modulated interaction and a coupling to a thermal reservoir. The combination of drive and dissipation leads to non-equilibrium steady states with a large number of doublon excitations, well above the maximum thermal-equilibrium value. We interpret this effect as an enhancement of local pairing correlations, providing analytical arguments based on a Floquet Hamiltonian. Remarkably, this Hamiltonian shows a tendency to develop long-range staggered superconducting correlations. This suggests the possibility of realizing th…
