Interaction-enhanced antiferromagnetic correlations in a Kondo ladder with a gapped band structure

Tatsuya Kaneko; Ritsuki Hirabayashi; Yutaka Akagi

Home/Archive/arXiv

arXiv · 2610.31142

Interaction-enhanced antiferromagnetic correlations in a Kondo ladder with a gapped band structure

Tatsuya Kaneko·Ritsuki Hirabayashi·Yutaka Akagi

View original source ↗Read source document ↗Export metadata ↓

Abstract

We investigate magnetic correlations in the two-leg Kondo-Hubbard ladder using the density-matrix renormalization group method. We focus on a parameter regime in which the noninteracting electronic system has a narrow indirect band gap. In this regime, there is no Fermi surface, and the conventional Fermi-surface-based Ruderman-Kittel-Kasuya-Yosida picture is not directly applicable; magnetic correlations between localized spins become weaker as the noninteracting band gap increases. We find that a moderate on-site Coulomb interaction enhances the antiferromagnetic correlations between localized spins. This enhancement, which is also seen in the staggered magnetization induced by a pinning field at the edges, occurs for both ferromagnetic and antiferromagnetic Kondo couplings. Our results show that electron-electron interactions can enhance magnetic correlations between localized spins even when the underlying noninteracting electronic structure is gapped, suggesting an interaction-driven route to magnetic instabilities in narrow-gap Kondo-lattice systems.

Explore related subjects

cond-mat.str-el

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

Tatsuya Kaneko, Ritsuki Hirabayashi, Yutaka Akagi. 2026-10-22. Interaction-enhanced antiferromagnetic correlations in a Kondo ladder with a gapped band structure. https://arxiv.org/abs/2610.31142

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Benchmarking the accuracy of superconducting pair-pair correlations within Constrained Path Quantum Monte Carlo

Ground state properties of the Hubbard model are of fundamental importance to understand the mechanism of unconventional superconductivity in the high-T_c cuprates and other materials. One of the most powerful numerical methods for strongly interacting models is quantum Monte Carlo, which however faces a fundamental limitation, the Fermion sign problem. The sign problem can be mitigated using approximate methods such as Constrained Path Monte Carlo, where the sign of the overlap with a trial wavefunction is constrained to remain positive. Beyond the constraint, additional approximations must be made in order to measure observables for operators that do not commute with the Hamiltonian. We examine critically the most commonly used approximation, back propagation, as well as a recently proposed constraint release measurement technique. In comparisons with a variety of systems that can be solved numerically exactly by other methods, we find that back propagation tends to underestimate long-range superconducting pair-pair correlations. Except in special cases such as one dimension, back propagation introduces an uncontrolled approximation even when the exact trial wavefunction is used. The constraint release technique can provide accurate results, with the disadvantages that it much more computationally expensive and reintroduces the sign problem.

cond-mat.str-el↗

arXiv2026

Correlation-Driven Ballistic Exciton Expansion in a Moiré Bose-Fermi Mixture

Moiré superlattices of transition-metal dichalcogenides (TMDs) host strongly interacting Bose-Fermi mixtures in which bosonic excitons coexist with correlated electron lattices. Using ultrafast, time- and energy-resolved photoluminescence (PL) microscopy, we show that strong exciton-electron and exciton-exciton repulsion can enable ballistic exciton transport in a WSe$_2$/WS$_2$ heterobilayer. This ballistic transport is energy selective: repulsive interactions populate higher-energy moiré exciton bands, including the doubly occupied exciton state XX and the exciton-electron co-localized state Xe, exhibiting mean-squared displacement (MSD) with a quadratic time dependence, MSD $\propto t^2$. Transport in the Xe band is jointly governed by exciton and electron correlations. Exciton correlations suppress relaxation into the lower-energy localized exciton state, while generalized Wigner-crystal (GWC) order at fractional electron fillings enhances Auger recombination and the group velocity of the ballistic expansion. A two-dimensional Bose-Fermi Hubbard model solved using time-dependent mean-field methods qualitatively reproduces the measured exciton transport and time-dependent response. It further confirms that strong cross-species interactions allow the electron crystal to perforate the exciton Mott background, enhancing exciton motion. Our results establish moiré TMDs as highly tunable platforms for realizing strongly interacting Bose-Fermi mixtures.

cond-mat.str-el↗

arXiv2026

Lattice dynamics and structural correlations in antiferromagnet SrLaCoNbO$_6$ double perovskite

We report a detailed temperature-dependent Raman spectroscopy and Co $K$-edge extended x-ray absorption fine structure (EXAFS) study of the insulating antiferromagnetic double perovskite SrLaCoNbO$_6$. Interestingly, pronounced changes in the phonon frequencies, linewidths, and intensities are observed around 60~K, well above the long-range antiferromagnetic ordering temperature, $T_{\rm N} \approx 15$~K. These anomalies indicate a modification of the lattice dynamics that may involve local structural distortions, short-range magnetic correlations, or an interplay between them. Additional changes in both high- and low-energy Raman modes are detected near 160--180~K via variations in phonon intensities and linewidths, together with changes in the Fano asymmetry of selected low-energy modes. The asymmetric line shapes of these modes are well described phenomenologically by Fano profiles and indicate coupling of the discrete phonons to an underlying continuum, whose possible microscopic origins are discussed. Moreover, the EXAFS analysis reveals correlated changes in bond distances and Debye--Waller factors around the Co ions near 60~K and 160~K, indicating subtle local structural distortions at temperatures corresponding to the Raman anomalies. The combined Raman and EXAFS results therefore demonstrate a close correlation between anomalous lattice dynamics and local structural evolution in SrLaCoNbO$_6$.

cond-mat.str-el↗