Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2609.13124

Magnon-induced hybridization brightens excitons in ferromagnetic semiconductors

Man-Yat Chu·Mona Berciu
View original source ↗Read source document ↗Export metadata ↓

Abstract

Excitons in magnetic semiconductors have energies and spin structures that are sensitive to the underlying magnetic order. We study this coupling in a minimal one-dimensional lattice model of a conduction electron and a valence hole moving in a ferromagnetic background of localized quantum spins, treating the electron, the hole, and the magnon(s) as explicitly resolved degrees of freedom. At zero temperature, spin conservation closes the relevant Hilbert subspaces at the one- or two-magnon level, so the model can be solved essentially exactly with a real-space Green's function method. Comparison against a frozen-spin approximation in which the local moments are replaced by their ordered values identifies which effects are due to emission and absorption of quantum magnons. A frozen background already lifts the spin degeneracy of the exciton and, if the two carriers couple with different strengths to the local moments, it mixes the singlet with the spin-zero triplet exciton. The emission and absorption of quantum magnons goes qualitatively further: it splits and shifts the exciton energies nonlinearly in the exchange coupling even when all frozen-spin effects vanish; for carriers with unequal hopping integrals, it hybridizes the singlet and spin-zero triplet excitons, thereby brightening the dark triplet; and it increases the exciton radius, which in turn enhances the magnon dressing by removing an on-site cancellation. These quantum effects are therefore strongest for extended, Wannier-like excitons, which is precisely the regime that is commonly modeled assuming a static (frozen-spin) magnetic order.

Explore related subjects

cond-mat.str-el

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Man-Yat Chu, Mona Berciu. 2026-09-11. Magnon-induced hybridization brightens excitons in ferromagnetic semiconductors. https://arxiv.org/abs/2609.13124

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

KEEP EXPLORING

Related papers

arXiv2026

Spontaneous Parity Breaking in Quantum Antiferromagnets on the Triangular Lattice

Frustration on the triangular lattice has long been a source of intriguing and often debated phases in many-body systems. Although symmetry analysis has been employed, the role of the seemingly trivial parity symmetry has received little attention. In this work, we show that phases induced by frustration are systematically shaped by an implicit rule-of-thumb associated with spontaneous parity breaking in weak longitudinal field. This principle enables us to anticipate and rationalize the regimes and conditions under which nontrivial phases emerge. For the spin-$S$ antiferromagnetic XXZ model, we demonstrate that a controversial parity-broken phase appears at intermediate values of $S$. In bilayer systems, enhanced frustration leads to additional phases, such as supersolids, whose properties can be classified by their characteristic parity features. Benefiting from our improved tensor network contraction techniques, we confirm these results through large-scale tensor-network calculations. This study offers an alternative viewpoint and a systematic approach for examining the interplay between spin, symmetry, and frustration in many-body systems.

cond-mat.str-el↗
arXiv2026

Directional Criticality and Higher-Order Flatness: Designing Van Hove Singularities in Three Dimensions

Van Hove singularities (VHSs) play a pivotal role in driving correlated electronic phenomena. Traditional classifications focus only on critical points where the band gradient vanishes in all directions. Here we establish a unified classification of VHSs in three-dimensional systems, characterized by the number of vanishing gradient components and Hessian eigenvalues: ordinary ($M$-type), higher-order ($T_1$, $T_2$, $T_3$), noncritical ordinary ($N_0$, $N_1$, $N_2$), and noncritical higher-order ($S_1$, $S_2$) types. Noncritical VHSs exhibit directional quenching: the gradient vanishes in a two-dimensional subspace while remaining finite along the orthogonal direction, yielding finite density-of-states enhancements with distinct energy dependencies. Using an $s$-orbital tight-binding model on the pyrochlore lattice with spin-orbit coupling, we demonstrate that all singularity classes emerge at distinct high-symmetry points through controlled tuning of the hopping ratio. This work establishes directional criticality and higher-order flatness as design principles for tailoring density-of-states enhancements in three-dimensional quantum materials.

cond-mat.str-el↗
arXiv2026

Quantum Rotors on the Fuzzy Sphere and the Cubic CFT

The three-dimensional cubic conformal field theory governs the critical behaviour of Heisenberg magnets with cubic anisotropy. Studying this theory non-perturbatively is challenging, because its most easily accessible observables are numerically very close to those of the more symmetric $O(3)$ model. In this work, we overcome this difficulty using the fuzzy sphere regularisation method. By adding a cubic-invariant two-body interaction to the quantum rotor Hamiltonian used for the $O(3)$ model, we break the continuous rotational symmetry by construction and unambiguously isolate the cubic critical point. Using exact diagonalisation and the density matrix renormalisation group, we calculate the scaling dimensions of several key operators, including the leading scalar singlets, and resolve the splitting of the $O(3)$ rank-two traceless symmetric tensor into the $E_g$ and $T_{2g}$ representations of the cubic group. Our results are consistent with existing Monte Carlo, conformal perturbation theory, and $\varepsilon$ expansion benchmarks, demonstrating the power of the fuzzy sphere in resolving closely spaced universality classes.

cond-mat.str-el↗