Related papers: Goldstone modes in the emergent gauge fields of a …
Fractons are topological quasiparticles with limited mobility. While there exists a variety of models hosting these excitations, typical fracton systems require rather complicated many-particle interactions. Here, we discuss fracton…
Based on exact diagonalization data for finite quantum Heisenberg antiferromagnets on two frustrated lattices (two-leg ladder and bilayer) and analytical arguments we map low-energy degrees of freedom of the spin models in a magnetic field…
Frustrated quantum magnets can host a variety of exotic spin excitations, including fractionalized spin excitations coupled to emergent gauge fields at deconfined quantum critical points (DQCPs) and chiral magnons in altermagnets. Here, we…
The nature and effects of the Goldstone mode in the ordered phase of helical or chiral itinerant magnets such as MnSi are investigated theoretically. It is shown that the Goldstone mode, or helimagnon, is a propagating mode with a highly…
We use a semiclassical large-$S$ expansion to study a plateau at $1/3$ saturation in the magnetization curve of a frustrated ferrimagnet on a spatially anisotropic kagom\'{e} lattice. The spins have both ferromagnetic and antiferromagnetic…
We report on a Monte Carlo study of a diluted Ising antiferromagnet on a fcc lattice. This is a typical model example of a highly frustrated antiferromagnet, and we ask, whether sufficient random dilution of spins does produce a spin glass…
We study the energy-momentum relations of the Nambu-Goldstone modes in quantum antiferromagnetic Heisenberg models on a hypercubic lattice. This work is a sequel to the previous series about the models. We prove that the Nambu-Goldstone…
The Goldstone mode due to stripe or unidirectional charge-density-wave order in electron systems is found to have the same functional form as the one in classical smectic liquid crystals. It is very similar to the Goldstone mode that…
In the presence of quenched disorder, the interplay between local magnetic-moment formation and Anderson localization for electrons at a zero-temperature, metal-insulator transition (MIT) remains a long unresolved problem. Here, we study…
We study the Higgs condensation $H={\bar t}t$ mechanism in the Top-mode Standard Model at the next-to-leading order in 1/Nc. The calculation includes the effects of the Goldstone fields, but not the effects of the transverse components of…
Using a phenomenological Ginzburg-Landau theory for the magnetic conical cycloid state of a multiferroic, which has been recently reported in the cubic spinel CoCr$_{2}$O$_{4}$, we discuss its low-energy fluctuation spectrum. We identify…
We study the phase diagram of a bilayer quantum spin liquid model with Kitaev-type interactions on a square lattice. We show that the low energy limit is described by a $\pi$-flux Hubbard model with an enhanced SO(4) symmetry. The…
The fermionic Hubbard model, when combined with the ingredient of frustration, associated with the breaking of particle-hole symmetry, harbors a rich phase diagram. Aspects of theoretical findings associated with the nature of magnetism and…
Here we report the first inelastic neutron scattering study of the magnetic excitations in the incommensurate phase of a spin-Peierls material. The results on CuGeO3 provide direct evidence of a finite excitation gap, two sharp magnetic…
The spin-nematic state has proved elusive, due to the difficulty of observing the order parameter in experiment. In this article we develop a theory of spin excitations in a field-induced spin-nematic state, and use it to show how a…
In systems with competing interactions, continuous degeneracies can appear which are accidental, in that they are not related to any symmetry of the Hamiltonian. Accordingly, the pseudo-Goldstone modes associated with these degeneracies are…
We consider the spin-1/2 antiferromagnetic Heisenberg model on three frustrated lattices (the diamond chain, the dimer-plaquette chain and the two-dimensional square-kagome lattice) with almost dispersionless lowest magnon band. Eliminating…
Frustration refers to the inability to satisfy competing interactions simultaneously, often leading to a large number of degenerate ground states. This can suppress ordering tendencies, sometimes resulting in a spin liquid phase. An…
Spin excitations in an ordered Heisenberg magnet are magnons--bosons with spin 1. That may change when frustration and quantum fluctuations suppress the order and restore the spin-rotation symmetry. We show that spin excitations in the…
We investigate magnetic excitations in an $S=3/2$ Heisenberg model representing two-dimensional antiferromagnet ${\rm Ba_2CoGe_2O_7}$. In terahertz absorption experiment of the compound, Goldstone mode as well as novel magnetic excitations,…