Half-integer thermal quantum Hall conductance has recently been reported for the two-dimensional honeycomb material α-RuCl3 We found that half-integer plateau appears even a magnetic field with no out-of-plane components. The measured field-angular variation of quantized same sign structure as topological Chern number pure Kitaev spin liquid. This observation suggests non-Abelian order associated fractionalization local moments persists in presence non-Kitaev interactions α-RuCl3.

Finite-temperature ($T$) properties of a Kitaev model defined on honeycomb lattice are investigated by quantum Monte Carlo simulation, from the viewpoint fractionalization $S=1/2$ spins into two types Majorana fermions, itinerant and localized. In this system, entropy is released successively at well-separated $T$ scales, as clear indication thermal fractionalization. We show that high-$T$ crossover, which driven closely related with development nearest-neighbor spin correlations. On other...

Magnetic Skyrmions are swirling spin textures with topologically protected noncoplanarity. Recently, the topological number of unity have been extensively studied in both experiment and theory. We here show that a Skyrmion crystal an unusually high two is stabilized itinerant magnets at zero magnetic field. The results obtained for minimal Kondo lattice model on triangular by unrestricted large-scale numerical simulation variational calculations. find can be switched field as...

Noncollinear and noncoplanar magnetic textures including Skyrmions vortices act as emergent electromagnetic fields give rise to novel electronic transport properties. We here report a unified understanding of orderings from the spin-charge coupling in itinerant magnets. The mechanism has its roots effective multiple spin interactions beyond conventional Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism, which are ubiquitously generated electron systems with local moments. By carefully examining...

The Kitaev quantum spin liquid displays the fractionalization of spins into Majorana fermions. emergent edge current is predicted to manifest itself in form a finite thermal Hall effect, feature commonly discussed topological superconductors. Here we report on conductivity $\kappa_{xy}$ measurements $\alpha$-RuCl$_3$, candidate magnet with two-dimensional honeycomb lattice. In spin-liquid (Kitaev paramagnetic) state below temperature characterized by interaction $J_K/k_B \sim 80$ K, positive...

The quantum spin liquid is an exotic state of matter in magnets. This a analog helium that does not solidify down to the lowest temperature due strong fluctuations. In conventional fluids, and gas possess same symmetry adiabatically connect each other by bypassing critical end point. We find situation qualitatively different liquids realized three-dimensional Kitaev model; both gapless gapped phases at low temperatures are always distinguished from high-temperature paramagnet (spin gas)...

In the search for quantum spin liquids, candidate materials Kitaev model and its extensions have been intensively explored during past decade, as models realize exact liquids in ground state. Thus far, insulating magnets low-spin ${d}^{5}$ electron configuration under strong spin-orbit coupling studied realizing Kitaev-type bond-dependent anisotropic interactions between spin-orbital entangled Kramers doublets. To extend candidates, here we investigate systems a high-spin ${d}^{7}$...

Magnetic skyrmion is a topologically stable particle-like swirling spin texture potentially suitable for high-density information bit, which was first observed in noncentrosymmetric magnets with Dzyaloshinskii-Moriya interaction. Recently, nanometric has also been discovered centrosymmetric rare-earth compounds, and the identification of their formation mechanism further search nontrivial textures are highly demanded. Here, magnetic structures prototypical skyrmion-hosting tetragonal magnet...

We study the evolution of metals from Mott insulators in carrier-doped 2D Hubbard model using a cluster extension dynamical mean-field theory. While conventional metal is simply characterized by Fermi surface (pole Green function $G$), interference zero surfaces $G$ with pole becomes crucial doped insulators. Mutually interfering and are dramatically transferred over gap, when lightly holes synergetically loosen doublon-holon binding. The heart physics such as pseudogap, hole pockets, arcs,...

We investigate the ground-state phase diagram for ferromagnetic Kondo lattice model on a triangular by variational calculation various spin orderings up to four-site unit cell. find that noncoplanar four-sublattice ordering with finite scalar chirality emerges at and around 1/4 filling, in addition 3/4-filled case which was predicted be induced perfect nesting of Fermi surface. The 1/4-filling is stable wider range parameters than 3/4-filling one, includes large region gapped insulating...

We reveal the significance of kinetic-driven multiple-spin interactions hidden in geometrically-frustrated Kondo lattice models. Carefully examining perturbation terms spin-charge coupling up to fourth order, we find that a positive biquadratic interaction is critically enhanced and plays crucial role on stabilizing spin scalar chiral order near 1/4 filling triangular case. This generalized Kohn anomaly, appearing only when second-order inefficient because degeneracy under frustration. The...

The hallmark of the toroidal order $\mathbf{T}$ in solids is presence cross-coupling term $\mathbf{T}\ensuremath{\cdot}(\mathbf{H}\ifmmode\times\else\texttimes\fi{}\mathbf{E})$ free energy system that leads to antisymmetric magneto-electric effect. In last several years has attracted interest connection with multiferroic insulating materials. authors this manuscript show such an exotic can occur even metallic systems on lattice structures where spatial-inversion symmetry preserved globally...

In conventional insulating magnets, heat is carried by magnons and phonons. contrast, when the magnets harbor a quantum spin liquid state, emergent quasiparticles from fractionalization of spins can carry heat. Here, we investigate unconventional thermal transport yielded such exotic carriers, in both longitudinal transverse components, for Kitaev model, whose ground state exactly shown to be with fractional excitations described as itinerant Majorana fermions localized ${Z}_{2}$ fluxes. We...

We theoretically investigate the origin of square-type skyrmion crystal in centrosymmetric itinerant magnets, motivated from recent experimental finding GdRu$_2$Si$_2$ [N. D. Khanh $\mathit{et}$ $\mathit{al.}$, Nat. Nanotech. $\mathbf{15}$, 444 (2020)]. By simulated annealing for an effective spin model derived Kondo lattice on a square lattice, we find that composed superposition two helices is stabilized magnetic field by synergy between positive biquadratic, bond-dependent anisotropic,...

The Kitaev spin liquid provides a rare example of well-established quantum liquids in more than one dimension. It is obtained as the exact ground state model with bond-dependent anisotropic interactions. peculiar interactions can be yielded by synergy spin-orbit coupling and electron correlations for specific configuration lattice geometry, which known Jackeli-Khaliullin mechanism. Based on this mechanism, there has been fierce race materialization over last decade, but candidates have still...

Magnetic skyrmions were thought to be stabilised only in inversion-symmetry breaking structures, but skyrmion lattices recently discovered inversion symmetric Gd-based compounds, spurring questions of the stabilisation mechanism. A natural consequence a recent theoretical proposal, coupling between itinerant electrons and localised magnetic moments, is that are amenable detection using even non-magnetic probes such as spectroscopic-imaging scanning tunnelling microscopy (SI-STM). Here SI-STM...

We study noncoplanar magnetic ordering in frustrated itinerant magnets. For a family of Kondo square lattice models with classical local moments, we find that double-$Q$ vortex crystal has lower energy than the single-$Q$ helical order expected from Ruderman-Kittel-Kasuya-Yosida interaction whenever symmetry dictates four global maxima bare susceptibility. By expanding small exchange and degree noncoplanarity, demonstrate this state arises Fermi surface instability, it is generic for wide...

Experimental identification of quantum spin liquids remains a challenge, as the pristine nature is to be seen in asymptotically low temperatures. We here theoretically show that precursor appears dynamics paramagnetic state over wide temperature range. Using cluster dynamical mean-field theory and continuous-time Monte Carlo method, which are newly developed Majorana fermion representation, we calculate structure factor, relaxation rate nuclear magnetic resonance, susceptibility for...

We theoretically study noncoplanar spin textures in polar magnetic conductors. Starting from the Kondo lattice model with Rashba spin-orbit coupling, we derive an effective generalized Ruderman-Kittel-Kasuya-Yosida interactions including anisotropic and antisymmetric exchange interactions. By performing simulated annealing for model, find that a vortex crystal of N\'eel type is stabilized even absence field. Moreover, demonstrate Bloch-type crystal, which usually associated Dresselhaus can...

The magnetic hedgehog lattice (HL) is a noncoplanar texture with periodic array of monopoles and antimonopoles. Despite phenomenological numerical studies thus far, there remain open issues on the microscopic origin, especially respect to recent experimental findings two different types HLs even at zero field. Here, we study stability for an effective spin model long-range interactions arising from itinerant nature electrons. By variational calculations simulated annealing, find that are...

We theoretically investigate multiple-$Q$ spin textures, which are composed of superpositions density waves with different wave numbers, for an effective model centrosymmetric itinerant magnets. Our focus is on the interplay between biquadratic interactions arising from spin-charge coupling and magnetic anisotropy caused by spin-orbit coupling. Taking into account two types anisotropy, single-ion bond-dependent we elucidate phase diagrams archetypal triangular-lattice system in absence...