Evolution of magnetic correlation in doped Hubbard model with altermagnetic spin splitting
School of Science, Harbin Institute of Technology, Shenzhen（哈尔滨理工大学深圳校区理学院）；Shenzhen Key Laboratory of Advanced Functional Carbon Materials Research and Comprehensive Application（深圳市先进功能碳材料研究及综合应用重点实验室）；Department of Physics, City University of Hong Kong（香港城市大学物理系）；Department of Physics, Jiangsu University（江苏大学物理系）
Yinlong Li, Rana Imran Mushtaq, Ji Liu, Wing Chi Yu, Xiaosen Yang, Cho-Tung Yip, Ho-Kin Tang
The evolution of magnetic correlation in strongly correlated electron systems with altermagentic spin splitting remains largely unexplored. Here we investigate how spin splitting generated by spin-dependent next-nearest-neighbor hopping t' reshapes the Fermi surface nesting and van Hove singularities in the two-dimensional square-lattice Hubbard model, leading evolution of magnetic instabilities. Using the constrained-path quantum Monte Carlo method, we find the dominant magnetic correlation as functions of the filling and t'/t by computing the momentum-resolved spin structure factor. The analysis reveals a transition from antiferromagnetic (π,π) order in the isotropic, half-filled system to non-collinear spiral (π,q) order upon increasing the spin-dependent anisotropy or doping away from half-filling, ultimately entering a short-range correlation regime where stripe and spiral correlation coexist. These findings highlight a possible route to realizing spiral correlation in altermagnetic systems, potentially providing a platform for spintronic devices that exploit non-collinear spin textures.
We study the dynamical behavior of doped electronic systems subject to a global ramp of the repulsive Hubbard interaction. We start with formulating a real-time generalization of the fluctuation-exchange approximation. Implementing this numerically, we investigate the weak-coupling regime of the Hubbard model both in the electron-doped and hole-doped regimes. The results show that both local and nonlocal (momentum-dependent) observables evolve toward a thermal state, although the temperature of the final state depends on the ramp duration and the chemical doping. We further reveal a momentum-d…
We derived a simple metal-insulator criterion in analytical form for the doped Mott-Hubbard materials. Its readings closely related to the orbital and spin nature of the ground states of the unit cell. The available criterion readings (metal or insulator) in the paramagnetic phase points to the possibility of the insulator state of doped materials with the forbidden first removal electron states. According to its physical meaning the result is similar to Wilsons criterion in the itinerant electron systems. An application of the criterion to the high-Tc cuprates discussed.
Local spin fluctuations provide the glue for orbital-singlet spin-triplet pairing in the doped Mott insulating regime of multi-orbital Hubbard models. At large Hubbard repulsion $U$, the pairing susceptibility is nevertheless very low, because the pairing interaction cannot overcome the suppression of charge fluctuations. Using nonequilibrium dynamical mean field simulations of the two-orbital Hubbard model, we show that out of equilibrium the pairing susceptibility in this large-$U$ regime can be strongly enhanced by creating a photo-induced population of the relevant charge states, and that …
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University（斯坦福材料能源科学研究所、SLAC国家加速器实验室和斯坦福大学）；Department of Physics and Astronomy, California State University, Northridge（加州州立大学北岭分校物理与天文学系）
We have performed large-scale density-matrix renormalization group studies of the lightly doped Hubbard model on the honeycomb lattice on long three and four-leg cylinders. We find that the ground state of the system upon lightly doping is consistent with that of a superconducting state with coexisting quasi-long-range superconducting and charge density wave orders. Both the superconducting and charge density wave correlations decay as a power law at long distances with corresponding exponents $K_{sc}<2$ and $K_c<2$. On the contrary, the spin-spin and single-particle correlations decay exponen…
We study the Hubbard model on a square lattice, using the dynamical vertex approximation and the parquet approximation. These methods allow us to describe the mutual interference of spin-fluctuations in the particle-hole channel and superconducting fluctuations in the cooperon channel in an unbiased way. For small dopings we find predominant commensurable antiferromagnetic spin- and d-wave superconducting fluctuations; for larger doping incommensurate antiferromagnetic spin fluctuations are concomitant to triplet s-wave superconducting fluctuations.
Strange or bad metallic transport, defined by its incompatibility with conventional quasiparticle pictures, is a theme common to strongly correlated materials and ubiquitous in many high temperature superconductors. The Hubbard model represents a minimal starting point for modeling strongly correlated systems. Here we demonstrate strange metallic transport in the doped two-dimensional Hubbard model using determinantal quantum Monte Carlo calculations. Over a wide range of doping, we observe resistivities exceeding the Mott-Ioffe-Regel limit with linear temperature dependence. The temperatures …
We demonstrate the existence of an insulating phase in the three-legged Hubbard ladder at two-thirds filling. In this phase chargons are bound because the physics within a unit cell favors the formation of triplets. The resultant moments lead to a ground state in the Haldane phase, a symmetry protected topological state of matter. In this purely fermionic model, reflection is protecting but time reversal and dihedral symmetries are not, in contrast to spin models.
School of Physical Science and Technology, ShanghaiTech University（上海科技大学物理科学与技术学院）；Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory and Stanford University（斯坦福大学材料能源科学研究所，SLAC国家加速器实验室和斯坦福大学）；Department of Materials Science and Engineering, Stanford University（斯坦福大学材料科学与工程系）
We have studied the ground state properties of Hubbard model on long six-leg square cylinders with doped hole concentration per site $5.55\% \leq δ\leq 12.5\%$ using density-matrix renormalization group. By keeping a large number of states for long system sizes, we find that the nature of the ground state is remarkably sensitive to the presence of next-nearest-neighbor electron hopping $t'$. In the positive $t'$ side, we find a robust $d$-wave superconducting (SC) phase characterized by coexisting quasi-long-range SC and charge density wave (CDW) correlations. Without $t'$ the ground state for…
Hirsch's dynamic Hubbard model describes the effect of orbital expansion with occupancy by coupling the doublon operator to an auxiliary boson. We use the nonequilibrium dynamical mean field method to study the properties of doublon and hole carriers in this model in the strongly correlated regime. In particular, we discuss how photodoping leads to doublon and hole populations with different effective temperatures, and we analyze the relaxation behavior as a function of the boson coupling and boson energy. In the polaronic regime, the nontrivial energy exchange between doublons, holes and boso…
Motivated by the current interest in the understanding of the Mott insulators away from half filling, observed in many perovskite oxides, we study the Mott metal-insulator transition (MIT) in the doped Hubbard-Holstein model using the Hatree-Fock mean field theory. The Hubbard-Holstein model is the simplest model containing both the Coulomb and the electron-lattice interactions, which are important ingredients in the physics of the perovskite oxides. In contrast to the half-filled Hubbard model, which always results in a single phase (either metallic or insulating), our results show that away …
By using the constrained-phase quantum Monte Carlo method, we performed a systematic study of the pairing correlations in the ground state of the doped Kane-Mele-Hubbard model on a honeycomb lattice. We find that pairing correlations with $d+id$ symmetry dominate close to half filling, but pairing correlations with $p+ip$ symmetry dominate as hole doping moves the system below three-quarters filling. We correlate these behaviors of the pairing correlations with the topology of the Fermi surfaces of the non-interacting problem. We also find that the effective pairing correlation is enhanced gre…
In this paper, we have systematically studied the single hole problem in two-leg Hubbard and $t$-$J$ ladders by large-scale density-matrix renormalization group calculations. We found that the doped hole in both models behaves similarly with each other while the three-site correlated hopping term is not important in determining the ground state properties. For more insights, we have also calculated the elementary excitations, i.e., the energy gaps to the excited states of the system. In the strong rung limit, we found that the doped hole behaves as a Bloch quasiparticle in both systems where t…
We derive the disorder vs. doping phase diagram of the doped Hubbard model via Dynamical Mean Field Theory combined with Typical Medium Theory, which allows the description of both Mott (correlation driven) and Anderson (disorder driven) metal-insulator transitions. We observe a transition from a metal to an Anderson-Mott insulator for increasing disorder strength at all interactions. In the weak correlation regime and rather small doping, the Anderson-Mott insulator displays properties which are alike to the ones found at half-filling. In particular, this phase is characterized by the presenc…
We present a non-perturbative, divergence-free series expansion of Green's functions using effective operators. The method is especially suited for computing correlators of complex operators as a series of correlation functions of simpler forms. We apply the method to study low-energy excitations in resonant inelastic x-ray scattering (RIXS) in doped one- and two-dimensional single-band Hubbard models. The RIXS operator is expanded into polynomials of spin, density, and current operators weighted by fundamental x-ray spectral functions. These operators couple to different polarization channels…
Using determinant quantum Monte Carlo (DQMC) simulations, we systematically study the doping dependence of the crossover from one to two dimensions and its impact on the magnetic properties of the Hubbard model. A square lattice of chains is used, in which the dimensionality can be tuned by varying the interchain coupling $t_\perp$. The dynamical spin structure factor and static quantities, such as the static spin susceptibility and nearest-neighbor spin correlation function, are characterized in the one- and two-dimensional limits as a benchmark. When the dimensionality is tuned between these…
While both the hole and electron doped cuprates can exhibit $d_{x^2-y^2}$-wave superconductivity, the local distribution of the doped carriers is known to be significantly different with the doped holes going primarily on the O sites while the doped electrons go on the Cu sites. Here we report the results of density matrix renormalization calculations for a three-orbital model of a CuO$_2$ lattice. In addition to the asymmetric dependence of the intra-unit-cell occupation of the Cu and O for hole and electron doping, we find important differences in the longer range spin and charge correlation…
Bad-Metal (BM) behavior featuring linear temperature dependence of the resistivity extending to well above the Mott-Ioffe-Regel (MIR) limit is often viewed as one of the key unresolved signatures of strong correlation. Here we associate the BM behavior with the Mott quantum criticality by examining a fully frustrated Hubbard model where all long-range magnetic orders are suppressed, and the Mott problem can be rigorously solved through Dynamical Mean-Field Theory. We show that for the doped Mott insulator regime, the coexistence dome and the associated first-order Mott metal-insulator transiti…
We discuss the rich phase diagram of doped AB2 $t-J$ chains by using data from density matrix renormalization group and exact diagonalization techniques. The $J$ vs $δ$ (hole doping) phase diagram exhibits regions of itinerant ferrimagnetism, incommensurate, resonating valence bond and Nagaoka states, phase separation, and Luttinger liquid (LL) physics. Several features are highlighted, such as the modulated ferrimagnetic structure, the occurrence of Nagaoka spin polarons in the underdoped regime and small values of $J=4t^2/U$, where $t$ is the first-neighbor hopping amplitude and $U$ is the o…
Low-energy photoexcitations inside the Mott gap in doped Hubbard and t-J ladders
Tokyo University of Science（东京科学大学）；Mawlana Bhashani Science and Technology University（毛拉纳·巴沙尼科学技术大学）；RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所新兴物质科学中心）；RIKEN Center for Computational Science (R-CCS)（理化学研究所计算科学中心）；RIKEN Center for Quantum Computing (RQC)（理化学研究所量子计算中心）；RIKEN Cluster for Pioneering Research (CPR)（理化学研究所先锋研究集群）
We investigate the excitation spectrum of strongly correlated sodium cobaltate within a realistic many-body description beyond dynamical mean-field theory (DMFT). At lower doping around $x$=0.3, rather close to Mott-critical half-filling, the single-particle spectral function of Na$_x$CoO$_2$ displays an upper Hubbard band which is captured within DMFT. Momentum-dependent self-energy effects beyond DMFT become dominant at higher doping. Around a doping level of $x\sim 0.67$, the incoherent excitations give way to finite-energy spin-polaron excitations in close agreement with optics experiments…
The damaging effect of strong electron-electron repulsion on regular, electron-phonon %$s$-wave superconductivity is a standard tenet. In spite of that, an increasing number of compounds such as fullerides and more recently alkali-doped aromatics exhibit %$s$-wave or presumably $s$ wave superconductivity despite very narrow bands and very strong electron repulsion. Here, we explore superconducting solutions of a model Hamiltonian inspired by the electronic structure of alkali doped aromatics. The model is a two-site, two-narrow-band metal with a single intersite phonon, leading to attraction-m…
