2026
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Salgado-Linares, I.; Mook, A.; Mangeolle, L.; Knolle, J. Thermal Hall conductivity from semiclassical spin dynamics simulations: Implementation and applications to chiral ferromagnets and Kitaev magnets Journal Article Phys. Rev. B 114, 125123 (2026). @article{salgado-linaresThermalHallConductivity2026,
title = {Thermal Hall conductivity from semiclassical spin dynamics simulations: Implementation and applications to chiral ferromagnets and Kitaev magnets},
author = {I. Salgado-Linares and A. Mook and L. Mangeolle and J. Knolle},
url = {https://link.aps.org/doi/10.1103/b1r9-1l3f},
doi = {10.1103/b1r9-1l3f},
year = {2026},
date = {2026-08-21},
urldate = {2026-08-21},
journal = {Phys. Rev. B},
volume = {114},
number = {12},
pages = {125123},
publisher = {American Physical Society},
abstract = {We investigate thermal Hall transport in magnetic systems, using semiclassical spin dynamics simulations. Building on a linear response framework, we discuss the intricacies of computing the thermal Hall conductivity from real-time energy current correlations and the energy magnetization. We then apply this methodology to two models: a square-lattice chiral magnet with in-plane Dzyaloshinskii-Moriya interaction, and the antiferromagnetic Kitaev model in a field. Our results demonstrate the efficiency of semiclassical spin dynamics to study thermal Hall transport capturing quantitative effects beyond the simple intrinsic noninteracting approximation. They can serve as a benchmark for comparison with experiments in regimes where nonlinearities from magnon-magnon interactions and strong thermal fluctuations play a crucial role.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We investigate thermal Hall transport in magnetic systems, using semiclassical spin dynamics simulations. Building on a linear response framework, we discuss the intricacies of computing the thermal Hall conductivity from real-time energy current correlations and the energy magnetization. We then apply this methodology to two models: a square-lattice chiral magnet with in-plane Dzyaloshinskii-Moriya interaction, and the antiferromagnetic Kitaev model in a field. Our results demonstrate the efficiency of semiclassical spin dynamics to study thermal Hall transport capturing quantitative effects beyond the simple intrinsic noninteracting approximation. They can serve as a benchmark for comparison with experiments in regimes where nonlinearities from magnon-magnon interactions and strong thermal fluctuations play a crucial role. |  |
Srivastava, A.; Birnkammer, S.; Sim, G.; Knap, M.; Knolle, J. Theory of nonlinear spectroscopy of quantum magnets Journal Article Phys. Rev. B 113, 184421 (2026), datadoi: 10.5281/zenodo.14938103. @article{srivastavaTheoryNonlinearSpectroscopy2026,
title = {Theory of nonlinear spectroscopy of quantum magnets},
author = {A. Srivastava and S. Birnkammer and G. Sim and M. Knap and J. Knolle},
url = {https://link.aps.org/doi/10.1103/2rfx-8ql6},
doi = {10.1103/2rfx-8ql6},
year = {2026},
date = {2026-05-07},
urldate = {2026-05-01},
journal = {Phys. Rev. B},
volume = {113},
number = {18},
pages = {184421},
publisher = {American Physical Society},
abstract = {Two-dimensional coherent spectroscopy (2DCS) is an established method for characterizing molecules and has been proposed in the terahertz regime as a tool for probing exotic excitations of quantum magnets; however, the precise nature of the coupling between pump field and spin degrees of freedom has remained unclear. Here, we develop a general response theory of 2DCS and show how magnetoelectric as well as polarization couplings contribute to 2DCS in addition to the typically assumed magnetization. We propose experimental protocols to probe the presence of polarization couplings, for instance, from exchange-striction or spin-current mechanism, when the electric field couples to quadratic terms in spin operators. We provide example calculations for the paradigmatic twisted Kitaev chain material CoNb2O6 and highlight the crucial role of contributions from cross-coupling between polarization and magnetic nonlinear susceptibilities. Our work paves the way for systematic studies of light-matter couplings in quantum magnets and for establishing 2DCS as a versatile tool for probing fractional excitations of exotic magnetic quantum phases.},
note = {datadoi: 10.5281/zenodo.14938103},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional coherent spectroscopy (2DCS) is an established method for characterizing molecules and has been proposed in the terahertz regime as a tool for probing exotic excitations of quantum magnets; however, the precise nature of the coupling between pump field and spin degrees of freedom has remained unclear. Here, we develop a general response theory of 2DCS and show how magnetoelectric as well as polarization couplings contribute to 2DCS in addition to the typically assumed magnetization. We propose experimental protocols to probe the presence of polarization couplings, for instance, from exchange-striction or spin-current mechanism, when the electric field couples to quadratic terms in spin operators. We provide example calculations for the paradigmatic twisted Kitaev chain material CoNb2O6 and highlight the crucial role of contributions from cross-coupling between polarization and magnetic nonlinear susceptibilities. Our work paves the way for systematic studies of light-matter couplings in quantum magnets and for establishing 2DCS as a versatile tool for probing fractional excitations of exotic magnetic quantum phases. | |
2025
|
Papaefstathiou, I.; Knolle, J.; Bañuls, M. C. Real-time scattering in the lattice Schwinger model Journal Article Phys. Rev. D 111, 014504 (2025). @article{papaefstathiou_real-time_2025,
title = {Real-time scattering in the lattice Schwinger model},
author = {I. Papaefstathiou and J. Knolle and M. C. Bañuls},
url = {https://link.aps.org/doi/10.1103/PhysRevD.111.014504},
doi = {10.1103/PhysRevD.111.014504},
year = {2025},
date = {2025-01-15},
urldate = {2025-01-15},
journal = {Phys. Rev. D},
volume = {111},
number = {1},
pages = {014504},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
| |
2024
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Jin, H. -K.; Knolle, J. Floquet Prethermal Order by Disorder Journal Article Phys. Rev. Research 6, L042033 (2024). @article{jin_floquet_2024,
title = {Floquet Prethermal Order by Disorder},
author = {H. -K. Jin and J. Knolle},
url = {https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.L042033},
doi = {10.1103/PhysRevResearch.6.L042033},
year = {2024},
date = {2024-11-04},
urldate = {2024-11-01},
journal = {Phys. Rev. Research},
volume = {6},
pages = {L042033},
abstract = {Frustrated magnets can have accidental ground state degeneracies which may be lifted by various forms of disorder, for example in the form of thermal or quantum fluctuations. This order by disorder (ObD) paradigm is well established in equilibrium and here is generalized to Floquet many-body systems. Investigating a periodically-driven XXZ-compass model on the square lattice, we show that in a prethermal regime, dynamical fluctuations induced by high-frequency drives select a discrete set of states out of a degenerate ground state manifold of the lowest order Floquet Hamiltonian chosen as initial states. Remarkably, prior to the ObD selection, an unusual fluctuating regime emerges leading to a prethermalization timescale scaling linearly with the drive frequency. We argue that prethermal ObD with its unusual approach to the selected states is a generic phenomenon of driven frustrated systems and confirm it in the paradigmatic $J_1-J_2$ XX model.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Frustrated magnets can have accidental ground state degeneracies which may be lifted by various forms of disorder, for example in the form of thermal or quantum fluctuations. This order by disorder (ObD) paradigm is well established in equilibrium and here is generalized to Floquet many-body systems. Investigating a periodically-driven XXZ-compass model on the square lattice, we show that in a prethermal regime, dynamical fluctuations induced by high-frequency drives select a discrete set of states out of a degenerate ground state manifold of the lowest order Floquet Hamiltonian chosen as initial states. Remarkably, prior to the ObD selection, an unusual fluctuating regime emerges leading to a prethermalization timescale scaling linearly with the drive frequency. We argue that prethermal ObD with its unusual approach to the selected states is a generic phenomenon of driven frustrated systems and confirm it in the paradigmatic $J_1-J_2$ XX model. | |
Birnkammer, S.; Knolle, J.; Knap, M. Signatures of domain-wall confinement in Raman spectroscopy of Ising spin chains Journal Article Phys. Rev. B 110, 134408 (2024), datadoi: 10.5281/zenodo.8252835. @article{birnkammerSignaturesDomainwallConfinement2024a,
title = {Signatures of domain-wall confinement in Raman spectroscopy of Ising spin chains},
author = {S. Birnkammer and J. Knolle and M. Knap},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.134408},
doi = {10.1103/PhysRevB.110.134408},
year = {2024},
date = {2024-10-03},
urldate = {2024-10-01},
journal = {Phys. Rev. B},
volume = {110},
number = {13},
pages = {134408},
abstract = {Mesonic bound states of domain walls (DWs) can be stabilized in quasi-one-dimensional magnetic compounds. Here, we theoretically study the Raman light scattering response of a twisted Kitaev chain with tilted magnetic fields as a minimal model for confinement in CoNb2O6. By both numerical matrix product states and few-DW variational states, we show that confinement-induced bound states directly manifest themselves as sharp peaks in the Raman response. Remarkably, by tuning the polarization of the incident light field, we demonstrate that the Raman response offers insights into the intrinsic symmetry of the bound-state wave function.},
note = {datadoi: 10.5281/zenodo.8252835},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Mesonic bound states of domain walls (DWs) can be stabilized in quasi-one-dimensional magnetic compounds. Here, we theoretically study the Raman light scattering response of a twisted Kitaev chain with tilted magnetic fields as a minimal model for confinement in CoNb2O6. By both numerical matrix product states and few-DW variational states, we show that confinement-induced bound states directly manifest themselves as sharp peaks in the Raman response. Remarkably, by tuning the polarization of the incident light field, we demonstrate that the Raman response offers insights into the intrinsic symmetry of the bound-state wave function. | |
Jin, H. -K.; Kadow, W.; Knap, M.; Knolle, J. Kinetic ferromagnetism and topological magnons of the hole-doped Kitaev spin liquid Journal Article npj Quantum Mater. 9, 65 (2024), datadoi: (10.5281/zenodo.8370778). @article{jinKineticFerromagnetismTopological2024,
title = {Kinetic ferromagnetism and topological magnons of the hole-doped Kitaev spin liquid},
author = {H. -K. Jin and W. Kadow and M. Knap and J. Knolle},
doi = {10.1038/s41535-024-00678-8},
year = {2024},
date = {2024-09-04},
urldate = {2024-09-01},
journal = {npj Quantum Mater.},
volume = {9},
number = {1},
pages = {65},
abstract = {We study the effect of hole doping on the Kitaev spin liquid (KSL) and find that for ferromagnetic (FM) Kitaev exchange K the system is very susceptible to the formation of a FM spin polarization. Through density matrix renormalization group simulations on finite systems, we uncover that the introduction of a single hole, corresponding to ≈1% hole doping for the system size we consider, with a hopping strength of just t textasciitilde 0.28K is enough to disrupt fractionalization and polarize the spins in the [001] direction due to an order-by-disorder mechanism. Taking into account a material relevant FM anisotropic exchange Γ drives the polarization towards the [111] direction via a transition into a topological FM state with chiral magnon excitations. We develop a parton mean-field theory incorporating fermionic holons and bosonic magnons, which accounts for the doping induced FM phases and topological magnon excitations. We discuss experimental implications for Kitaev candidate materials.},
note = {datadoi: (10.5281/zenodo.8370778)},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We study the effect of hole doping on the Kitaev spin liquid (KSL) and find that for ferromagnetic (FM) Kitaev exchange K the system is very susceptible to the formation of a FM spin polarization. Through density matrix renormalization group simulations on finite systems, we uncover that the introduction of a single hole, corresponding to ≈1% hole doping for the system size we consider, with a hopping strength of just t textasciitilde 0.28K is enough to disrupt fractionalization and polarize the spins in the [001] direction due to an order-by-disorder mechanism. Taking into account a material relevant FM anisotropic exchange Γ drives the polarization towards the [111] direction via a transition into a topological FM state with chiral magnon excitations. We develop a parton mean-field theory incorporating fermionic holons and bosonic magnons, which accounts for the doping induced FM phases and topological magnon excitations. We discuss experimental implications for Kitaev candidate materials. | |
Das, P.; Leeb, V.; Knolle, J.; Knap, M. Realizing altermagnetism in fermi-hubbard models with ultracold atoms Journal Article Phys. Rev. Lett. 132, 263402 (2024), datadoi: 10.5281/zenodo.10391823. @article{dasRealizingAltermagnetismFermihubbard2024,
title = {Realizing altermagnetism in fermi-hubbard models with ultracold atoms},
author = {P. Das and V. Leeb and J. Knolle and M. Knap},
url = {https://doi.org/10.1103/PhysRevLett.132.263402},
doi = {10.1103/PhysRevLett.132.263402},
year = {2024},
date = {2024-06-26},
urldate = {2024-06-01},
journal = {Phys. Rev. Lett.},
volume = {132},
number = {26},
pages = {263402},
abstract = {Altermagnetism represents a type of collinear magnetism, that is in some aspects distinct from ferromagnetism and from conventional antiferromagnetism. In contrast to the latter, sublattices of opposite spin are related by spatial rotations and not only by translations and inversions. As a result, altermagnets have spin-split bands leading to unique experimental signatures. Here, we show theoretically how a 𝑑-wave altermagnetic phase can be realized with ultracold fermionic atoms in optical lattices. We propose an altermagnetic Hubbard model with anisotropic next-nearest neighbor hopping and obtain the Hartree-Fock phase diagram. The altermagnetic phase separates in a metallic and an insulating phase and is robust over a large parameter regime. We show that one of the defining characteristics of altermagnetism, the anisotropic spin transport, can be probed with trap-expansion experiments.},
note = {datadoi: 10.5281/zenodo.10391823},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Altermagnetism represents a type of collinear magnetism, that is in some aspects distinct from ferromagnetism and from conventional antiferromagnetism. In contrast to the latter, sublattices of opposite spin are related by spatial rotations and not only by translations and inversions. As a result, altermagnets have spin-split bands leading to unique experimental signatures. Here, we show theoretically how a 𝑑-wave altermagnetic phase can be realized with ultracold fermionic atoms in optical lattices. We propose an altermagnetic Hubbard model with anisotropic next-nearest neighbor hopping and obtain the Hartree-Fock phase diagram. The altermagnetic phase separates in a metallic and an insulating phase and is robust over a large parameter regime. We show that one of the defining characteristics of altermagnetism, the anisotropic spin transport, can be probed with trap-expansion experiments. | |
