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Spin-rotation coupling (SRC) is a fundamental phenomenon that connects electronic spins with the rotational motion of a medium. We elucidate the Einstein-de Haas (EdH) effect and its inverse with SRC as the microscopic mechanism using the dynamic spin-lattice equations derived by elasticity theory and Lagrangian formalism. By applying the coupling equations to an iron disk in a magnetic field, we exhibit the transfer of angular momentum and energy between spins and lattice, with or without damping. The timescale of the angular momentum transfer from spins to the entire lattice is estimated by our theory to be on the order of 0.01 ns, for the disk with a radius of 100 nm. Moreover, we discover a linear relationship between the magnetic field strength and the rotation frequency, which is also enhanced by a higher ratio of Young's modulus to Poisson's coefficient. In the presence of damping, we notice that the spin-lattice relaxation time is nearly inversely proportional to the magnetic field. Our explorations will contribute to a better understanding of the EdH effect and provide valuable insights for magneto-mechanical manufacturing.

Local constraint in lattice gauge theory provides an exotic mechanism inducing disorder-free localization. However, the nonequilibrium dynamics in the non-Hermition lattice gauge model has not been well understood. Here, we investigate the quench dynamics of spinless fermions with nonreciprocal hopping in the $\mathbb{Z}_2$ gauge field formed from the bond spins. Based on the effective model from duality mapping, the non-Hermitian skin effect, disorder-free localization-delocalization transition, and the real-complex transition of eigenenergies are explored systematically. By identifying the diverse scaling behaviors of quantum mutual information for fermions and spins, we predict that the non-Hermition quantum disentangled liquid presents both in localized and delocalized phase with completely different physical nature, the first comes from the $\mathbb{Z}_2$ gauge field and the second originates from the non-Hermitian skin effect. We finally show that the nonreciprocal dissipation of fermions leads the quantum information flowing from the fermions to spins. Our results provide new insights to the nonequilibrium dynamics in the gauge field, and can be experimentally verified using ultracold atoms in optical lattices., 13pages, 10 figures

Recently, high-Tc superconductivity is reported in the bulk nickelate $\mathrm{La_3Ni_2O_7}$ at pressures above 14 GPa. Here, we study an eleven-band Hubbard model with hopping parameters derived from \textit{ab initio} calculations of $\mathrm{La_3Ni_2O_7}$, by employing large scale determinant quantum Monte Carlo and cellular dynamical mean-field theory methods. Our result suggests that the superexchange couplings in this system are comparable to that of cuprates. The superexchange couplings between the intra-layer $d_{x^2-y^2}$ orbitals are comparable to its cuprates counterpart, and that between the inter-layer $d_{3z^2-r^2}$ orbitals are substantially stronger than the former. The system is a charge transfer insulator as hole concentration becomes four per site at large Hubbard $U$. Upon hole doping, two low-energy spin-singlet bands emerge in the system exhibiting distinct correlation properties: while the one composed of the out-of-plane Ni-$d_{3z^2-r^2}$ and O-$p_z$ orbitals demonstrates strong antiferromagnetic correlations and narrow effective bandwidth, the in-plane singlet band consisting of the Ni-$d_{x^2-y^2}$ and O-$p_x / p_y$ orbitals is in general more itinerant. Over a broad range of hole doping, the doped holes occupy primarily the $d_{x^2-y^2}$ and $p_x / p_y$ orbitals, as the $d_{3z^2-r^2}$ and $p_z$ orbitals retain underdoped. We propose an effective $ t-J$ model to capture the relevant physics and discuss the implications of our result for comprehending the $\mathrm{La_3Ni_2O_7}$ superconductivity.

We study topological magnons on an anisotropic square-hexagon-octagon (SHO) lattice which has been found by a two-dimensional Biphenylene network (BPN). We propose the concepts of type-II Dirac magnonic states where new schemes to achieve topological magnons are unfolded without requiring the Dzyaloshinsky-Moriya interactions (DMIs). In the ferromagnetic states, the topological distinctions at the type-II Dirac points along with one-dimensional (1D) closed lines of Dirac magnon nodes are characterized by the $\mathbb{Z}_2$ invariant. We find pair annihilation of the Dirac magnons and use the Wilson loop method to depict the topological protection of the band-degeneracy. The Green's function approach is used to calculte chiral edge modes and magnon density of states (DOS). We introduce the DMIs to gap the type-II Dirac magnon points and demonstrate the Dirac nodal loops (DNLs) are robust against the DMIs within a certain parameter range. The topological phase diagram of magnon bands is given via calculating the Berry curvature and Chern number. We find that the anomalous thermal Hall conductivity gives connection to the magnon edge current. Furthermore, we derive the differential gyromagnetic ratio to exhibit the Einstein-de Haas effect (EdH) of magnons with topological features.

The newly discovered Ruddlesden-Popper bilayer La$_3$Ni$_2$O$_7$ reaches an remarkable superconducting transition temperature $T_c$ = 80 K under a pressure of above 14 GPa. Here we propose a minimal bilayer two-orbital model of the high-pressure phase of La$_3$Ni$_2$O$_7$. Our model is constructed with the Ni-3d$_{x^2-y^2}$, 3d$_{3z^2-r^2}$ orbitals by using Wannier downfolding of the density functional theory calculations, which captures the key ingredients of the material, such as band structure and Fermi surface topology. There are two electron pockets $\alpha$, $\beta$ and one hole pocket $\gamma$ on the Fermi surface, in which the $\alpha$, $\beta$ pockets show mixing of two orbitals, while the $\gamma$ pocket is associated with Ni-d$_{3z^2-r^2}$ orbital. The RPA spin susceptibility reveals a magnetic enhancement associating to the d$_{3z^2-r^2}$ state. A higher energy model with O-p orbitals is also provided for further study.

We investigate the experimental signatures of Raman spectroscopy of bi- and tri-magnon excitations in the distorted triangular lattice antiferromagnets alpha-LCr2O4 (L=Sr, Ca). We utilize spin wave theory to analyze the nearly 120 degree spin-3/2 spiral ordered antiferromagnetic ground state to compute the single-magnon density of states, single-magnon dispersion, and bimagnon and trimagnon Raman spectra (polarized and unpolarized). It is found that Raman scattering is capable of capturing the effect of the rotonlike M and M' points on the bimagnon Raman spectrum. Our calculation confirms the connection between single-magnon rotonlike excitation energy and bimagnon Raman excitation spectrum observed experimentally. The roton energy minimum in momentum space is half of the energy of a bimagnon excitation signal. The experimental magnetic Raman scattering result displays two peaks which have a Raman shift of 15 meV and 40 meV, respectively. Theoretical modeling and analysis of the experimental spectrum of alpha-SrCr2O4 within our distorted Heisenberg Hamiltonian lattice suggests that the low-energy peak at 15 meV is associated with the bimagnon excitation, whereas the high-energy peak around 40 meV is primarily a trimagnon excitation. Based on our fitting procedure we propose a new set of magnetic interaction parameters for alpha-SrCr2O4. These parameters reproduce not only the experimental Raman spectrum, but also the inelastic neutron scattering response (including capturing high energy magnon branches). We also compute the unpolarized bimagnon and trimagnon Raman spectra for alpha-CaCr2O4. Furhtermore, we found that the polarization sensitivity of Raman spectrum can be utilized to distinguish the bi- and tri-magnon excitation channels., 11 pages, 4 figures

We study the phase diagram and the dynamical spin structure factor of the spin-1/2 J1-J3 Heisenberg model on the square lattice using density matrix renormalization group, exact diagonalization (ED), and cluster perturbation theory (CPT). By extrapolating the order parameters and studying the level crossings of the low-lying energy and entanglement spectra, we obtain the phase diagram of this model and identify a narrow region of quantum spin liquid (QSL) phase followed by a plaquette valence-bond solid (PVBS) state in the intermediate region, whose nature has been controversial for many years. More importantly, we use CPT and ED to study the dynamical spin structure factor in the QSL and the PVBS phase. In the QSL phase, the high-energy magnon mode completely turns into some dispersive weak excitations around the X and M points. For the PVBS phase, the low-energy spectrum is characterized by a gapped triplet excitation, and at the high energy, we find another branch of dispersive excitation with broad continua, which is unlike the plaquette phase in the 2x2 checkerboard model. In the latter case, the second branch of excitation is nearly flat due to the weak effective interactions between the local excitations of the plaquettes. And in the J1-J3 Heisenberg model, the uniform interactions and the spontaneously translational symmetry breaking of the PVBS phase make the difference in the excitation spectra., 14 pages, 14 figures

We study the $S>1/2$ antiferromagnetic Heisenberg model on the 1/5-depleted square lattice as a function of the ratio of the intra-plaquette coupling to the inter-plaquette coupling. Using stochastic series expansion quantum Monte Carlo simulations, we numerically identify three quantum phases, including the dimer phase, N\'eel phase and plaquette valence bond solid phase. We also obtain the accurate quantum critical points that belong to the O(3) universality class using the large-scale finite-size scaling. Most importantly, we study the dynamic spin structure factors of different phases, which can be measured by inelastic neutron scattering experiments. The low-energy excitations can be explained as triplons in the dimer phase and plaquette valence bond solid phase. While in the N\'eel phase, the more prominent magnon mode can be found as the spin magnitude increases. Furthermore, we find a broader continuum at smaller $S$, which may be the dynamical signature of nearly deconfined spinon excitations.

Quasi-one-dimensional iron chalcogenides possess various magnetic states depending on the lattice distortion, electronic correlations, and presence of defects. We present neutron diffraction and inelastic neutron scattering experiments on the spin ladder compound BaFe$_{2-\delta}$S$_{1.5}$Se$_{1.5}$ with $\sim$6% iron vacancies. The data reveal that long-range magnetic order is absent, while the characteristic magnetic excitations that correspond to both the stripe- and block-type antiferromagnetic correlations are observed. First-principles calculations support the existence of both stripe and block-type antiferromagnetic short-range order in the experimental sample. The disappearance of long-range magnetic order may be due to the competition between these two magnetic orders, which is greatly enhanced for a certain concentration of iron vacancies, which we calculate to be about 6%, consistent with the measured iron vacancy concentration. Our results highlight how iron vacancies in the iron-based spin ladder system strongly influence the magnetic ground state., Comment: 8 pages, 6 figures