Antiferromagnetism and superconductivity are often viewed as competing orders in correlated electron systems. Here, we demonstrate that kinetic frustration in hole motion facilitates their coexistence within the square-lattice repulsive Hubbard model. Combining exact analytical solutions on tailored geometries with large-scale numerical simulations, we reveal a robust pairing mechanism: Holes on opposite sublattices behave as if they carry opposite effective charges due to spin singlet formation from kinetic frustration. This emergent property suppresses phase separation and fosters a coherent [Formula: see text]-wave superconducting channel embedded within a long-range antiferromagnetic background. Our findings establish a minimal yet broadly applicable framework for stabilizing strong-coupling superconductivity in doped Mott insulators.
Antiferromagnetism and superconductivity are often viewed as competing orders in correlated electron systems. Here, we demonstrate that kinetic frustration in hole motion facilitates their coexistence within the square-lattice repulsive Hubbard model. Combining exact analytical solutions on tailored geometries with large-scale numerical simulations, we reveal a robust pairing mechanism: Holes on opposite sublattices behave as if they carry opposite effective charges due to spin singlet formation from kinetic frustration. This emergent property suppresses phase separation and fosters a coherent [Formula: see text]-wave superconducting channel embedded within a long-range antiferromagnetic background. Our findings establish a minimal yet broadly applicable framework for stabilizing strong-coupling superconductivity in doped Mott insulators.
We propose a pairing mechanism between holes in the dilute limit of doped frustrated Mott insulators. Hole pairing arises from a hole-hole-magnon three-body bound state. This pairing mechanism has its roots on single-hole kinetic energy frustration, which favors antiferromagnetic (AFM) correlations around the hole. We demonstrate that the AFM polaron (hole-magnon bound state) produced by a single hole propagating on a field-induced polarized background is strong enough to bind a second hole. The effective interaction between these three-body bound states is repulsive, implying that this pairing mechanism is relevant for superconductivity.
We study repulsive Hubbard and t-J type systems on a square lattice (long believed to capture certain quintessential aspects of the high temperature superconductors). These models (alongside the parent compounds of the high temperature superconductors) are antiferromagnetic in the absence of hole doping. As we illustrate, a unifying underlying principle for the dynamics of holes introduced by doping rationalizes the emergence of nonuniform electronic structures- "stripes" and possible pairing tendencies therein. Specifically, our analysis invokes the following (numerically verified) sublattice parity principle: a strong antiferromagnetic background forces injected holes to hop in steps of two such that they always remain on the same sub lattice. When applied to a domain wall in an antiferromagnet, this simple principle naturally gives rise to (bond centered) stripes. We demonstrate that the holes are self-consistently localized on stripes. Extending this picture, we then show that the holes on a stripe favor the formation of pairs on neighboring rungs or sites. Throughout this work much emphasis is placed on the problem of a two leg ladder immersed in a staggered magnetic field. Although we will focus on the square lattice, our considerations may be extended to similar electronic structures appearing in other models on bipartite lattices when these exhibit antiferromagnetic correlations with an underlying sublattice structure.
The pairing mechanism in doped antiferromagnets is essential for understanding high-temperature superconductivity. In this work, we investigate the pairing mechanism in bosonic doped antiferromagnets via large-scale density matrix renormalization group calculations of the bosonic $t\ensuremath{-}J$ model. We discover a pair density wave (PDW) coexists with the antiferromagnetic (AFM) order forming a ``supersolid'' at small doping. The pairing is attributed to a hidden many-body Berry phase that introduces the sole ``sign problem'' into this bosonic model and imposes quantum phase frustration to the spin-charge interference pattern. Only via tightly pairing of doped holes can such frustration be most effectively erased in an AFM background. By contrast, the pairing vanishes as the Berry phase is trivialized in the ferromagnetic condensate at larger doping or switched off into the Bose-Hubbard model at large U. The present pairing mechanism---distinct from the conventional mechanisms based on Fermi surface instabilities---may provide a different perspective and new insights for understanding the complex nature of doped Mott insulators and is promising to be probed on qudit-based quantum simulators such as ultracold Rydberg atom arrays.
Magnon-Mediated Superconductivity in the Infinite-U Triangular Lattice
We demonstrate that the infinite-U triangular-lattice Hubbard model supports a superconducting state built from tightly bound Cooper pairs composed of two holes and one magnon (2h1m). Building on the seminal prediction of repulsively bound 2h1m states, we show that next-nearest-neighbor hopping t2 coherently mixes symmetry-related configurations, stabilizing an s-wave bound state with substantial binding energy and a light effective mass. Large-scale DMRG calculations at finite doping identify a magnetization plateau corresponding to a gas of such bound states and quasi--long--range superconducting order with power-law 2h1m pair correlations. Our results establish a magnon-mediated superconducting mechanism driven by kinetic frustration, with immediate detectable signatures for moiré Hubbard materials and ultracold-atom simulators.
Inspired by the recent experimental advances in cold atom quantum simulators, we explore the experimentally implemented bosonic t-t^{'}-J model on the square lattice using large-scale density matrix renormalization group simulations. By tuning the doping level δ and hopping ratio t^{'}/t, we uncover six distinct quantum phases, several of which go far beyond the conventional paradigm of phase-coherent superfluidity (SF) expected for bosonic systems. In particular, in the presence of antiferromagnetic (AFM) order, doped holes are tightly bound into pairs, giving rise to a pair density wave phase at low doping and small |t^{'}/t|, which is suppressed on the t^{'}<0 side, resulting in a disordered pair density wave state that lacks coherence of either individual bosons or pairs. Upon further doping, bosons can regain phase coherence and form an SF* state, characterized by condensation at emergent incommensurate momenta concurrent with an incommensurate magnetic order. On the t^{'}>0 side, the sign-induced kinetic frustration inherently disfavors local AFM correlations, leading to a phase separation in which doped holes cluster into ferromagnetic (FM) domains spatially separated by undoped AFM regions. Upon further doping, this inhomogeneous state evolves into a uniform SF+xy-FM phase. Finally, we propose a concrete experimental scheme to realize both signs of t^{'}/t in Rydberg tweezer arrays, with an explicit mapping between model parameters and experimentally accessible regimes. Our results reveal competing and intertwined orders in doped antiferromagnets, which are relevant to central issues in high-T_{c} superconductivity, reflecting the frustrated interplay between doped holes and spin background.
The two-dimensional Hubbard model is widely believed to capture key ingredients of high-T_{c} superconductivity in cuprate materials. However, compelling evidence remains elusive. In particular, various magnetic orders may emerge as strong competitors of superconducting orders. Here, we study the ground state properties of the doped two-dimensional t-t^{'} Hubbard model on a square lattice via the infinite projected entangled-pair state method with U(1) or SU(2) spin symmetry. The former is compatible with antiferromagnetic orders, while the latter forbids them. Therefore, we obtain by comparison a detailed understanding of the magnetic impact on superconductivity. Moreover, an additional t^{'} term accommodates the particle-hole asymmetry, which facilitates studies on the discrepancies between electron- and hole-doped systems. We demonstrate that (i) a positive t^{'}/t significantly amplifies the strength of superconducting orders; (ii) at sufficiently large doping levels, the t-t^{'} Hubbard model favors a uniform state with superconducting orders instead of stripe states with charge and spin modulations; and (iii) the enhancement of magnetic frustration, by increasing either the strength of next-nearest neighbor interactions or the charge doping, impairs stripe orders and helps stabilize superconductivity.