We study the magnetism and lattice distortion of Fe_{1+y}Te_{1-x}Se_x with a general field theory formalism, motivated by recent neutron scattering experiments. Besides the Ising nematic order parameter which can be naturally defined in the 1111 and 122 materials, We show that the collinear order observed in $\mathrm{Fe_{1+y}Te}$ materials is stabilized by an extra Ising order parameter which doubles the generalized unit cell of the system. By tuning this Ising order parameter, one can drive a transition between collinear and noncollinear spin density wave orders, both of which are observed in the FeTe family. The nature of the quantum and classical phase transitions are also studied in this field theory formalism, with lattice strain tensor fluctuation considered.
We investigate ground states of $s$=1/2 Heisenberg antiferromagnets on the eleven two-dimensional (2D) Archimedian lattices by using the coupled cluster method. Magnetic interactions and quantum fluctuations play against each other subtly in 2D quantum magnets and the magnetic ordering is thus sensitive to the features of lattice topology. Archimedean lattices are those lattices that have 2D arrangements of regular polygons and they often build the underlying magnetic lattices of insulating quasi-two-dimensional quantum magnetic materials. Hence they allow a systematic study of the relationshi…
The Fe3+ lattice in the Bi2Fe4O9 compound is found to materialize the first analogue of a magnetic pentagonal lattice. Due to its odd number of bonds per elemental brick, this lattice, subject to first neighbor antiferromagnetic interactions, is prone to geometric frustration. The Bi2Fe4O9 magnetic properties have been investigated by macroscopic magnetic measurements and neutron diffraction. The observed non-collinear magnetic arrangement is related to the one stabilized on a perfect tiling as obtained from a mean field analysis with direct space magnetic configurations calculations. The pecu…
Our resistivity, magnetoresistance, magnetization and specific heat data provide unambiguous evidence that CeRhSn2 is a Kondo lattice system which undergoes magnetic transition below 4 K.
This is a comment for a paper entitled "Low-Temperature Magnetic Properties of the Kondo Lattice Model in One Dimension" [S.Minami and H.Kawamura, JPSJ84,044702(2015)].
We study the stability of some strongly frustrated antiferromagnetic spin lattices in high magnetic fields against lattice distortions. In particular, we consider a spin-s anisotropic Heisenberg antiferromagnet on the square-kagomé and kagomé lattices. The independent localized magnons embedded in a ferromagnetic environment, which are the ground state at the saturation field, imply lattice instabilities for appropriate lattice distortions fitting to the structure of the localized magnons. We discuss in detail the scenario of this spin-Peierls instability in high magnetic fields which essentia…
We study theoretically the lattice instability in the spin gap systems under magnetic field. With the magnetic field larger than a critical value h_{c1}, the spin gap is collapsed and the magnetization arises. We found that the lattice distortion occurs in the spin-ladder at an incommensurate wavevector corresponding to the magnetization, while it does not occur in the Haldane system. At low temperatures the magnetization curve shows a first order phase transition with this lattice distortion.
Numerical investigation on the thermodynamic properties of an Ising spin Kondo lattice model on a kagome lattice is reported. By using Monte Carlo simulation, we investigated the magnetic phases at 1/3-filling. We identified two successive transitions from high-temperature paramagnetic state to a Kosterlitz-Thouless-like phase in an intermediate temperature range and to a partially disordered phase at a lower temperature. The partially disordered state is characterized by coexistence of antiferromagnetic hexagons and paramagnetic sites with period $\sqrt3 \times \sqrt3$. We compare the results…
We report the results of Cu and Cl nuclear magnetic resonance experiments (NMR) and thermal expansion measurements in magnetic fields in the coupled dimer spin system TlCuCl3. We found that the field-induced antiferromagnetic transition as confirmed by the splitting of NMR lines is slightly discontinuous. The abrupt change of the electric field gradient at the Cl sites, as well as the sizable change of the lattice constants, across the phase boundary indicate that the magnetic order is accompanied by simultaneous lattice deformation.
Lattice Wigner crystal states stabilized by long-range Coulomb interactions have recently been realized in two-dimensional moiré materials. We employ large-scale unrestricted Hartree-Fock techniques to unveil the magnetic phase diagrams of honeycomb lattice Wigner crystals. For the three lattice filling factors with the largest charge gaps, n = 2/3, 1/2, 1/3, the magnetic phase diagrams contain multiple phases, including ones with non-collinear and non-coplanar spin arrangements. We discuss magnetization evolution with external magnetic field, which has potential as an experimental signature o…
Bi3Mn4O12(NO3), in which the Mn4+ ions carry S=3/2, is the first honeycomb lattice system that shows no long-range magnetic order. Using neutron scattering, we have determined that short-range antiferromagnetic correlations develop at low temperatures. Applied magnetic fields induce a magnetic transition, in which the short-range order abruptly expands into a long-range order.
We consider the Kondo-lattice model on the kagome lattice and study its weak-coupling instabilities at band filling fractions for which the Fermi surface has singularities. These singularites include Dirac points, quadratic Fermi points in contact with a flat band, and Van Hove saddle points. By combining a controlled analytical approach with large-scale numerical simulations, we demonstrate that the weak-coupling instabilities of the Kondo-lattice model lead to exotic magnetic orderings. In particular, some of these magnetic orderings produce a spontaneous quantum anomalous Hall state.
Exchange interaction tends to favor collinear or coplanar magnetic orders in rotationally invariant spin systems. Indeed, such magnetic structures are usually selected by thermal or quantum fluctuations in highly frustrated magnets. Here we show that a complex noncoplanar magnetic order with a quadrupled unit cell is stabilized by itinerant electrons on the pyrochlore lattice. Specifically we consider the Kondo-lattice and Hubbard models at quarter filling. The electron Fermi 'surface' at this filling factor is topologically equivalent to three intersecting Fermi circles. Perfect nesting of th…
The magnetic translation algebra plays an important role in the quantum Hall effect. Murthy and Shankar, arXiv:1207.2133, have shown how to realize this algebra using fermionic bilinears defined on a two-dimensional square lattice. We show that, in any dimension $d$, it is always possible to close the magnetic translation algebra using fermionic bilinears, whether in the continuum or on the lattice. We also show that these generators are complete in even, but not odd, dimensions, in the sense that any fermionic Hamiltonian in even dimensions that conserves particle number can be represented in…
Ground state properties of spinless, extended Falicov-Kimball model (FKM) on a finite size triangular lattice with orbital magnetic field normal to the lattice are studied using numerical diagonalization and Monte-Carlo simulation methods. We show that the ground state configurations of localized electrons strongly depend on the magnetic field. Magnetic field induces a metal to insulator transition accompanied by segregated phase to an ordered regular phase except at density $n_f = 1/2$ of localized electrons. It is proposed that magnetic field can be used as a new tool to produce segregated p…
We investigate the interplay between the formation of lattice and magnetic polaron in the case of a single hole in the antiferromagnetic background. We present an exact analytical solution of the Holstein-t-J model in infinite dimensions. Ground state energy, electron-lattice correlation function, spin bag dimension as well as spectral properties are calculated. The magnetic and hole-lattice correlations sustain each other, i.e. the presence of antiferromagnetic correlations favors the formation of the lattice polaron at lower value of the electron-phonon coupling while the polaronic effect co…
We succeeded in observing pressure-suppressed magnetic long range ordering (LRO) in the triangular lattice antiferromagnet CuFeO$_{2}$, using neutron diffraction experiments under an isotropic pressure. The magnetic LRO of the four-sublattice ground state under ambient pressure in CuFeO$_{2}$ almost disappears at the high pressure of 7.9 GPa, and is replaced by an incommensurate order with temperature-independent wave number of (0.192 0.192 1.5). The incommensurate wave number observed at 7.9 GPa corresponds to that observed just above the temperature at which lattice distortion and magnetic L…
An extended non-magnetic phase in the spin-1/2 Heisenberg antiferromagnet from the ruby to the maple-leaf lattice
Freie Universität Berlin（柏林自由大学）；University of Cologne（科隆大学）；Helmholtz-Zentrum Berlin für Materialien und Energie（柏林亥姆霍兹材料与能源中心）；Indian Institute of Technology Madras（马德拉斯印度理工学院）
A molecular Mott insulator $κ$-(ET)$_2$B(CN)$_4$ [ET = bis(ethylenedithio)tetrathiafulvalene] with a distorted triangular lattice exhibits a quantum disordered state with gapped spin excitation in the ground state. $^{13}$C nuclear magnetic resonance, magnetization, and magnetic torque measurements reveal that magnetic field suppresses valence bond order and induces long-range magnetic order above a critical field $\sim 8$ T. The nuclear spin-lattice relaxation rate $1/T_1$ shows persistent evolution of antiferromagnetic correlation above the transition temperature, highlighting a quantum spin…
Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The for…
The magnetic inhomogeneity of the A-phase in MnSi chiral magnet is identified for the first time from the precise measurements of transverse magnetoresistance (MR) anisotropy. The area inside the A-phase (A-phase core) corresponds to isotropic MR having no confinement to the MnSi crystal lattice. Per contra, the MR becomes anisotropic both on the border of the A-phase and in other magnetic phases, the strongest magnetic scattering being observed when external magnetic field applied along [001] or [00-1] directions. We argue here that the established MR features prove the presence of two differ…
Motivated by the mysteries of the heavy fermion quantum critical point, we investigate the competition between Kondo screening and magnetic ordering in the honeycomb Kondo lattice at half filling. We examine the destruction of the Kondo phase by proliferating vortex configurations in the Kondo hybridization order parameter. We find that there are zero modes associated with Kondo vortices. Condensing these vortices can lead to the antiferromagnetic phase.
We compare predictions of the mean-field theory of superconductivity for nearly antiferromagnetic and nearly ferromagnetic metals for cubic and tetragonal lattices. The calculations are based on the parametrization of an effective interaction arising from the exchange of magnetic fluctuations and assume that a single band is relevant for superconductivity. The results show that for comparable model parameters, the robustness of magnetic pairing increases gradually as one goes from a cubic structure to a more and more anisotropic tetragonal structure either on the border of antiferromagnetism o…
Magnetoelectric and magnetoelastic phenomena correlated with a phase transition into noncollinear magnetic phase have been investigated for single crystals of CuFeO2 with a frustrated triangular lattice. CuFeO2 exhibits several long-wavelength magnetic structures related to the spin frustration, and it is found that finite electric polarization, namely inversion symmetry breaking, occurs with noncollinear but not at collinear magnetic phases. This result demonstrates that the noncollinear spin structure is a key role to induce electric polarization, and suggests that frustrated magnets which o…
Synchrotron x-ray diffraction and resonant magnetic scattering experiments on single crystal DyMnO3 have been carried out between 4 and 40 K. Below TN(Dy) = 5K, the Dy magnetic moments order in a commensurate structure with propagation vector 0.5 b*. Simultaneous with the Dy magnetic ordering, an incommensurate lattice modulation with propagation vector 0.905 b* evolves while the original Mn induced modulation is suppressed and shifts from 0.78 b* to 0.81 b*. This points to a strong interference of Mn and Dy induced structural distortions in DyMnO3 besides a magnetic coupling between the Mn an…
The magnetic hedgehog lattice (HL), which was recently discovered in the $B$20-type chiral magnet MnSi$_{1-x}$Ge$_x$, is a topological spin texture with a periodic array of magnetic monopoles and anti-monopoles. Within the continuum approximation, the monopoles and anti-monopoles are predicted to move, collide, and pair annihilate in an applied magnetic field, but it remains unclear how the lattice discretization affects their motions. Here, we study the trajectories of monopoles and anti-monopoles in a lattice system by simulated annealing with field sweep. We show that the monopoles and anti…
Excitation spectra of square lattice Heisenberg antiferromagnets in magnetic fields are investigated by the spin-wave theory. It is pointed out that a rotonlike structure appears in a narrow range of magnetic fields, as a result of strong nonlinear effects. It is shown that the energy gap and the mass of the "roton" are quite sensitive to the magnetic field: the roton gap softens rapidly and eventually closes as a precursor of a quantum phase transition. The possibility of the experimental observation of the roton and a new ground state after its softening are discussed.
We consider the quantum spin-$s$ $XXZ$ Heisenberg antiferromagnet on the two- and three-dimensional pyrochlore lattices and examine a spin-Peierls mechanism of lowering the total energy by a lattice distortion in a high magnetic field. For the exact eigenstates consisting of several independent localized magnons in a ferromagnetic environment we show the existence of a spin-Peierls instability by rigorous analytical calculations. In addition we report on exact diagonalization data for finite two-dimensional pyrochlore lattices up to N=64 sites. We discuss a scenario of the field-tuned changes …
We report Hall, magnetic, heat capacity and doping studies from single crystals of Yb_14MnSb_11 and Yb_13.3La_0.7MnSb_11. These heavily doped semiconducting compounds are ferromagnetic below 53 K and 39 K respectively. The renormalization of the carrier mass from 2 me near room temperature to 15 me at 5 K, plus the magnetic evidence for partial screening of the Mn magnetic moments suggest that these compounds represent rare examples of an underscreened Kondo lattice with T_K = 350 K.
A quantum mean field theory of the pyrochlore lattice is presented. The starting point is not the individual magnetic ions, as in the usual Curie-Weiss mean field theory, but a set of interacting corner sharing tetrahedra. We check the consistency of the model against magnetic susceptibility data, and find a good agreement between the theoretical predictions and the experimental data. Implications of the model and future extensions are also discussed.
Scaling equations for the Kondo lattice in the paramagnetic and magnetically ordered phases are derived to two-loop order with account of spin dynamics. The results are applied to describe various mechanisms of the non-Fermi-liquid (NFL) behavior in the multichannel Kondo-lattice model where a fixed point occurs in the weak-coupling region. The corresponding temperature dependences of electronic and magnetic properties are discussed. The model describes naturally formation of a magnetic state with soft boson mode and small moment value. An important role of Van Hove singularities in the magnon…
The magnetic ground state phase diagram of the ferromagnetic Kondo-lattice model is constructed by calculating internal energies of all possible bipartite magnetic configurations of the simple cubic lattice explicitly. This is done in one dimension (1D), 2D and 3D for a local moment of S = 3/2. By assuming saturation in the local moment system we are able to treat all appearing higher local correlation functions within an equation of motion approach exactly. A simple explanation for the obtained phase diagram in terms of bandwidth reduction is given. Regions of phase separation are determined …
We have measured the electric resistivity, magnetoresistance, magnetic susceptibility and magnetization of the new Kondo-lattice compound Ce3Pd4Ge4. The electrical resistivity exhibits a rapid drop at temperatures below 6 K, while the magnetic susceptibility does not show any corresponding anomaly at that temperature. This phenomenon is similar to that of Ce3Pd20Ge6 which shows quadrupolar interation. We suggest that there is the possibility of quadrupolar interaction in the orthorhombic 4f-electron system Ce3Pd4Ge4. In addition, it is realized that the spin-dependent scattering effect is resp…
We study the magnetic order and excitations in strong spin-orbit coupled, Van Vleck-type, $d^4$ Mott insulators on a square lattice. Extending the previous work, we include the tetragonal crystal field splitting and explore its effects on magnetic phase diagram and magnon spectra. Two different ordered phases, with in-plane and out-of-plane orientation of the staggered moments, are found for the higher and lower values of the crystal field splitting, respectively. The magnetic excitation spectra for paramagnetic and magnetically ordered phases are calculated and discussed in the context of a c…
In order to study the magnetic properties of frustrated metallic systems, we present Quantum Monte Carlo data on the magnetic susceptibility of the Hubbard model on triangular and Kagome lattices. We show that the underlying lattice structure is important, and determines the nature and the doping dependence of the magnetic fluctuations. In particular, in the doped Kagome case we find strong short-range magnetic correlations, which makes the metallic Kagome systems a promising field for studies of superconductivity.
We study the spectral and magnetic properties of one-dimensional lattices filled with 2 to 4 fermions (with spin 1/2) per lattice site. We use a generalized Hubbard model that takes account all interactions on a lattice site, and solve the many-particle problem by exact diagonalization. We find an intriguing magnetic phase diagram which includes ferromagnetism, spin-one Heisenberg antiferromagnetism, and orbital antiferromagnetism.
The magnetic ground-state of copper metaborate is investigated by means of elastic neutron scattering.The magnetic structure of CuB2O4 is incommensurate with respect to the chemical lattice at T=1.8K and undergoes a continuous phase transition to a non-collinear commensurate antiferromagnetic state which is realized at T=10K. Close to the phase transition higher-order magnetic satellites are observed. Coexistence of long-range and short range magnetic order observed in both magnetic phases. This suggests that the association of the Dzyialoshinskii-Moriya interaction, lattice symmetry and tetra…
For a class of frustrated antiferromagnetic spin lattices (in particular, the square-kagomé and kagomé lattices) we discuss the impact of recently discovered exact eigenstates on the stability of the lattice against distortions. These eigenstates consist of independent localized magnons embedded in a ferromagnetic environment and become ground states in high magnetic fields. For appropriate lattice distortions fitting to the structure of the localized magnons the lowering of magnetic energy can be calculated exactly and is proportional to the displacement of atoms leading to a spin-Peierls lat…
Exploration of rare-earth (RE)-based Kagome lattice magnets with spin-orbital entangled jeff=1/2 moments will provide new platform for investigating the exotic magnetic phases. Here, we report a new family of RE3BWO9 (RE=Pr,Nd,Gd-Ho) boratotungstates with magnetic RE3+ ions arranged on Kagome lattice, and perform its structure and magnetic characterizations. This serial compounds crystallize in hexagonal coordinated structure with space group P63 (No.173), where magnetic RE3+ ions have distorted Kagomé lattice connections within the ab plane and stacked in a AB-type fashion along c axis. The i…
We propose theoretically that a magnetic field can realize spin-triplet superconductivity in repulsively interacting electron systems having strong ferromagnetic spin fluctuations. We confirm the general idea for the low-density Hubbard model on a triangular lattice, whose Fermi surface consists of disconnected pieces, by calculating the pairing susceptibility in a moderate magnetic field with the quantum Monte-Carlo method combined with the dynamical cluster approximation.
We theoretically propose that magnetic skyrmion, nanometric spin vortex characterized by a quantized topological number, can be electrically created on a thin-film specimen of chiral-lattice magnetic insulator within a few nanoseconds by applying an electric field via an electrode tip taking advantage of coupling between noncollinear skyrmion spins and electric polarizations. This finding will pave a route to utilizing multiferroic skyrmions as information carriers for low-energy-consuming magnetic storage devices without Joule-heating energy losses.
Assuming that the order parameter corresponds to an equal spin triplet pairing symmetry state, we calculate the effect of phase fluctuations in quasi-one-dimensional superconductors at high magnetic fields applied along the y (b') axis. We show that phase fluctuations can destroy the theoretically predicted triplet reentrant superconducting state, and that they are responsible for melting the magnetic field induced Josephson vortex lattice above a magnetic field dependent melting temperature Tm.
Detailed dynamics of a moving magnetic skyrmion lattice in MnSi observed using a small-angle neutron scattering under an alternating electric current flow
Quantum Heisenberg antiferromagnets on pyrochlore and checkerboard lattices in a strong external magnetic field are mapped onto hard-core lattice gases with an extended exclusion region. The effective models are studied by the exchange Monte Carlo simulations and by the transfer matrix method. The transition point and the critical exponents are obtained numerically for a square-lattice gas of particles with the second-neighbor exclusion, which describes a checkerboard antiferromagnet. The exact structure of the magnon crystal state is determined for a pyrochlore antiferromagnet.
We develop the cluster self-consistent field method incorporating both electronic and lattice degrees of freedom to study the origin of ferromagnetism in Cs$_{2}$AgF$_{4}$. After self-consistently determining the harmonic and anharmonic Jahn-Teller distortions, we show that the anharmonic distortion stabilizes the staggered x$^{2}$-z$^{2}$/y$^{2}$-z$^{2}$ orbital and ferromagnetic ground state, rather than the antiferromagnetic one. The amplitudes of lattice distortions, Q$_{2}$ and Q$_{3}$, the magnetic coupling strengthes, J$_{x,y}$, and the magnetic moment, are in good agreement with the ex…
We report a clear anomaly in the rf response of a tunnel-diode resonator measured in borocarbide crystals in dc fields along the $c-$axis. We associate the anomaly in the dynamic magnetic susceptibility, $χ$, with a structural transition in the vortex lattice. $χ$ is sensitive to the Campbell penetration depth $λ_{C}$ of the rf perturbation into the mixed state. $λ_{C}$ depends on the vortex lattice elastic moduli, which in turn depend on the vortex lattice structure. The high-field transition line is clearly mapped and shown to behave in agreement with theory.
This study examines the effect of distorted triangular magnetic interactions in the Kagome lattice. Using a Holstein-Primakoff expansion, we determine the analytical solutions for classical energies and the spin-wave modes for various magnetic configurations. By understanding the magnetic phase diagram, we characterize the changes in the spin waves and examine the spin distortions of the ferromagnetic (FM), Antiferrimagnetic (AfM), and 120$^{\circ}$ phases that are produced by variable exchange interactions and lead to various non-collinear phases, which provides a deeper understanding of the …
Magnetic field effects on single-particle energy bands (Hofstadter butterfly), Hall conductance, flat-band ferromagnetism, and magnetoresistance of two-dimensional Kagome lattices are studied. The flat-band ferromagnetism is shown to be broken as the flat-band has finite dispersion in the magnetic field. A metal-insulator transition induced by the magnetic field (giant negative magnetoresistance) is predicted. In the half-filled flat band, the ferromagnetic-paramagnetic transition and the metal-insulator one occur simultaneously at a magnetic field for strongly interacting electrons. All of th…
Magnetic and electronic states of an Ising-spin Kondo lattice model on a kagome lattice are investigated by a Monte Carlo simulation. In addition to the conventional ferromagnetic and ferrimagnetic orders, we show that this model exhibits several thermally-induced phases, such as partially disordered, Kosteritz-Thouless-like, and loop-liquid states. In the partially disordered state, we show that the magnetic transition is associated with the charge-gap formation. We find that the density of state shows characteristic peaks reflecting the underlying spin texture. In the loop-liquid state, we a…
Here, we report the synthesis and magnetic properties of a Yb-based triangular-lattice compound LiYbS$_2$. At low temperatures, it features an effective spin-$\frac{1}{2}$ state due to the combined effect of crystal electric field and spin orbit coupling. Magnetic susceptibility measurements and $^7$Li nuclear magnetic resonance experiments reveal the absence of magnetic long range ordering down to 2~K, which suggests a possible quantum spin liquid ground state. A dominant antiferromagnetic nearest neighbour exchange interaction $J/k_{\rm B}\simeq$ 5.3~K could be extracted form the magnetic su…
We use Schwinger boson mean field theory to study the antiferromagnetic spin-1/2 Heisenberg model on an anisotropic triangular lattice in the presence of a uniform external magnetic field. We calculate the field dependence of the spin incommensurability in the ordered spin spiral phase, and compare the results to the recent experiments in Cs$_{2}$CuCl$_{4}$ by Coldea et al. (Phys. Rev. Lett. 86, 1335 (2001)).
An effective-field theory based on the single-spin cluster has been used to study of a diluted spin-$1/2$ Ising antiferromagnet on the Kagome lattice with nearest-neighbor interactions. We observe five plateaus in the magnetization curve of the diluted antiferromagnet when a magnetic field is applied which is in agreement with Monte Carlo calculation. The effect of the site-dilution on the magnetic susceptibility is also investigated and discussed. In particular, we have found that the frustrated Kagome lattice inverse susceptibility fall to zero at $0$K.
Ordering of the frustrated classical Heisenberg model on the triangular-lattice with an incommensurate spiral spin structure is studied under magnetic fields by means of a mean-field analysis and a Monte Carlo simulation. Several types of multiple-q states including the "skyrmion-lattice" state is observed in addition to the standard single-q state. In contrast to the Dzyaloshinskii-Moriya interaction driven system, the present model allows both skyrmions and anti-skyrmions, together with a new thermodynamic phase where skyrmion and anti-skyrmion lattices form a domain state.
The thermal properties of antiferromagnetic films -- in particular, the square-lattice antiferromagnet -- subjected to an external magnetic field pointing into the direction of the staggered magnetization are explored. The effective field theory analysis of the free energy density is carried out to two-loop order. While the emphasis is on finite temperature, we also discuss the behavior of the magnetization and staggered magnetization at zero temperature. Our results imply that the staggered magnetization increases in presence of the magnetic field -- reminiscent of magnetic catalysis. Most re…
We propose utilizing the Cooper pair to induce magnetic frustration in systems of two-dimensional (2D) magnetic adatom lattices on s-wave superconducting surfaces. The competition between singlet electron correlations and the RKKY coupling is shown to lead to a variety of hidden order states that break the point-group symmetry of the 2D adatom lattice at finite temperature. The phase diagram is constructed using a newly developed effective bond theory [M. Schecter et al., Phys. Rev. Lett. 119, 157202 (2017)], and exhibits broad regions of long-range vestigial nematic order.
Motivated by a recent experimental demonstration of a chiral edge mode in an array of spinning gyroscopes, we theoretically study the coupled gyration modes of topological magnetic solitons, vortices and magnetic bubbles, arranged as a honeycomb lattice. The soliton lattice under suitable conditions is shown to support a chiral edge mode like its mechanical analogue, the existence of which can be understood by mapping the system to the Haldane model for an electronic system. The direction of the chiral edge mode is associated with the topological charge of the constituent solitons, which can b…
We present the theory of nonlinear ac magnetic response for the highly nonlinear regime of the chiral soliton lattice. Increasing of the dc magnetic field perpendicularly to the chiral axis results in crossover inside the phase, when nearly isolated $2π$-kinks are partitioned by vast ferromagnetic domains. Assuming that each of the kink reacts independently from the other ones to the external ac field, we demonstrate that internal deformations of such a kink give rise to the nonlinear response.
We demonstrate a fast numerical method of theoretical studies of skyrmion lattice or spiral order in magnetic materials with Dzyaloshinsky-Moriya interaction. The method is based on the Fourier expansion of the magnetization combined with a minimization of the free energy functional of the magnetic material in Fourier space, yielding the optimal configuration of the system for any given set of parameters. We employ a Lagrange multiplier technique in order to satisfy micromagnetic constraints. We apply this method to a system that exhibits, depending on the parameter choice, ferromagnetic, skyr…
