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تسجيل مستخدم جديدFingerprints of Kitaev physics in the magnetic excitations of honeycomb iridates
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In the quest for realizations of quantum spin liquids, the exploration of Kitaev materials - spin-orbit entangled Mott insulators with strong bond-directional exchanges - has taken center stage. However, in these materials the local spin-orbital j=1/2 moments typically show long-range magnetic order at low temperature, thus defying the formation of a spin-liquid ground state. Using resonant inelastic x-ray scattering (RIXS), we here report on a proximate spin liquid regime with clear fingerprints of Kitaev physics in the magnetic excitations of the honeycomb iridates alpha-Li2IrO3 and Na2IrO3. We observe a broad continuum of magnetic excitations that persists up to at least 300K, more than an order of magnitude larger than the magnetic ordering temperatures. We prove the magnetic character of this continuum by an analysis of the resonance behavior. RIXS measurements of the dynamical structure factor for energies within the continuum show that dynamical spin-spin correlations are restricted to nearest neighbors. Notably, these spectroscopic observations are also present in the magnetically ordered state for excitation energies above the conventional magnon excitations. Phenomenologically, our data agree with inelastic neutron scattering results on the related honeycomb compound RuCl3, establishing a common ground for a proximate Kitaev spin-liquid regime in these materials.
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We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev - Heisenberg model proposed for A2IrO3 (A=Li, Na) compounds. The spin-wave excitation spectrum, the sublattice magnetization, and the transition temperatures are calculated in the random ph
ase approximation (RPA) for four different ordered phases, observed in the parameter space of the model: antiferomagnetic, stripe, ferromagnetic, and zigzag phases. The N{e}el temperature and temperature dependence of the sublattice magnetization are compared with the experimental data on Na2IrO3.
We investigate the doping effects of magnetic and nonmagnetic impurities injected to the honeycomb iridate sample of Na2IrO3 . Both the doping result in changing the ordering temperature as well as the Curie-Weiss temperature of the parent sample as
a consequence of enhancement of the lattice frustration, screening of the Ir atoms and spin-orbit effects that reflects in the susceptibility and specific heat measurements. Our findings are corroborated by a detailed comparative study of various magnetic and nonmagnetic impurity atoms that have notable effects on different electronic properties of the doped compounds.
The complexity of the antiferromagnetic orders observed in the honeycomb iridates is a double-edged sword in the search for a quantum spin-liquid ground state: both attesting that the magnetic interactions provide many of the necessary ingredients, b
ut simultaneously impeding access. As a result, focus has been drawn to the unusual magnetic orders and the hints they provide to the underlying spin correlations. However, the study of any particular broken symmetry state generally provides little clue as to the possibilities of other nearby ground states cite{Anderson}. Here we use extreme magnetic fields to reveal the extent of the spin correlations in $gamma$-lithium iridate. We find that a magnetic field with a small component along the magnetic easy-axis melts long-range order, revealing a bistable, strongly correlated spin state. Far from the usual destruction of antiferromagnetism via spin polarization, the correlated spin state possesses only a small fraction of the total moment, without evidence for long-range order up to the highest attainable magnetic fields (>90 T).
We report the successful synthesis of single-crystals of the layered iridate, (Na$_{1-x}$Li$_{x}$)$_2$IrO$_3$, $0leq x leq 0.9$, and a thorough study of its structural, magnetic, thermal and transport properties. The new compound allows a controlled
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The fractionalization of elementary excitations in quantum spin systems is a central theme in current condensed matter physics. The Kitaev honeycomb spin model provides a prominent example of exotic fractionalized quasiparticles, composed of itineran
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