Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userEffect of delithiation on the dimer transition of the honeycomb-lattice ruthenate Li$_{2-x}$RuO$_3$
145
0
0.0
(
0
)
Added by
Marco Polo Jimenez Segura
Publication date
2016
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
The honeycomb-lattice ruthenate Li$_2$RuO$_3$ is made heavily Li-deficient by chemical oxidation by iodine. The delithiation triggers a different phase Li$_{2-x}$RuO$_3$, the D-phase, with superlattice. For the first time we disclose the magnetic and structural properties of the D-phase in the dimer-solid state. The low temperature magnetic susceptibility and the bond lengths indicate a bonding configuration consisting of both Ru$^{4+}$-Ru$^{4+}$ and Ru$^{5+}$-Ru$^{5+}$ dimers.
rate research
Read More
We report the synthesis and characterisation of polycrystalline Na$_2$RuO$_3$, a layered material in which the Ru$^{4+}$ ($4d^4$ configuration) form a honeycomb lattice. The optimal synthesis condition was found to produce a nearly ordered Na$_2$RuO$_3$ ($C2/c$ phase), as assessed from the refinement of the time-of-flight neutron powder diffraction. Magnetic susceptibility measurements reveal a large temperature-independent Pauli paramagnetism ($chi_0 sim 1.42(2)times10^{-3}$ emu/mol Oe) with no evidence of magnetic ordering down to 1.5 K, and with an absence of dynamic magnetic correlations, as evidenced by neutron scattering spectroscopy. The intrinsic susceptibility ($chi_0$) together with the Sommerfeld coeficient of $gamma=11.7(2)$ mJ/Ru mol K$^2$ estimated from heat capacity measurements, gives an enhanced Wilson ratio of $R_Wapprox8.9(1)$, suggesting that magnetic correlations may be present in this material. While transport measurements on pressed pellets show nonmetallic behaviour, photoemission spectrocopy indicate a small but finite density of states at the Fermi energy, suggesting that the bulk material is metallic. Except for resistivity measurements, which may have been compromised by near surface and interface effects, all other probes indicate that Na$_2$RuO$_3$ is a moderately correlated electron metal. Our results thus stand in contrast to earlier reports that Na$_2$RuO$_3$ is an antiferromagnetic insulator at low temperatures.
Li2RuO3 undergoes a structural transition at a relatively high temperature of 550 K with a distinct dimerization of Ru-Ru bonds on the otherwise isotropic honeycomb lattice. It exhibits a unique herringbone dimerization pattern with a largest ever reported value of the bond shrinkage of about ~ 0.5 r{A}. Despite extensive studies, both theoretical and experimental, however, its origin and its effect on physical properties still remain to be understood. In this work, using high quality single crystals we investigated the anisotropy of resistivity ($rho$) and magnetic susceptibility ($chi$) to find a very clear anisotropy: $rho$$_c*$ > $rho$$_b$ > $rho$$_a$ and $chi$$_b$ > $chi$$_a$ > $chi$$_c*$. For possible theoretical interpretations, we carried out density functional calculations to conclude that these anisotropic behavior is due to the correlation effects combined with the unique orbital structure and the dimerization of Ru 4d bands.
We consider the $(2+1)$-d $SU(2)$ quantum link model on the honeycomb lattice and show that it is equivalent to a quantum dimer model on the Kagome lattice. The model has crystalline confined phases with spontaneously broken translation invariance associated with pinwheel order, which is investigated with either a Metropolis or an efficient cluster algorithm. External half-integer non-Abelian charges (which transform non-trivially under the $mathbb{Z}(2)$ center of the $SU(2)$ gauge group) are confined to each other by fractionalized strings with a delocalized $mathbb{Z}(2)$ flux. The strands of the fractionalized flux strings are domain walls that separate distinct pinwheel phases. A second-order phase transition in the 3-d Ising universality class separates two confining phases; one with correlated pinwheel orientations, and the other with uncorrelated pinwheel orientations.
The control of the stoichiometry of Li$_{1+x}$Zn$_{2-y}$Mo$_3$O$_8$ was achieved by the solid-state-reaction. We found that the best sample that has the chemical composition Li$_{0.95(4)}$Zn$_{1.92(8)}$Mo$_3$O$_8$ was obtained from the starting nominal composition with Li : Zn : Mo : O = $(1+w)$ : $(2.8-w)$ : $3$ : $8.6$ with $w = -0.1$, indicating that the stoichiometry is greatly improved compared to those in the earlier reports. For larger $w$ detailed structural analysis indicates that the mixed sites of Li and Zn are preferentially occupied by Li atoms, as well as the fraction of the non-magnetic secondary phase Zn$_2$Mo$_3$O$_8$ decreases. Magnetic susceptibility of the improved stoichiometry powder samples shows a broad hump in the temperature range of 100 $< T <$ 200 K. This suggests that the development of antiferromagnetic correlations at the high temperatures is inherent to the ideal stoichiometric LiZn$_2$Mo$_3$O$_8$.
We report equilibrium and nonequilibrium optical measurements on the recently synthesized harmonic honeycomb iridate gamma-Li$_2$IrO$_3$ (LIO), as well as the layered honeycomb iridate Na$_2$IrO$_3$ (NIO). Using Fourier transform infrared microscopy we performed reflectance measurements on LIO, from which we obtained the optical conductivity below 2 eV. In addition we measured the photoinduced changed in reflectance, Delta R, as a function of time, t, temperature, T, and probe field polarization in both LIO and NIO. In LIO, Delta R(t,T) is anisotropic and comprised of three T dependent components. Two of these components are related to the onset of magnetic order and the third is related to a photoinduced population of metastable electronic excited states. In NIO, Delta R(t,T) has a single T dependent component that is strikingly similar to the electronic excitation component of Delta R in LIO. Through analysis and comparison of Delta R(t,T) for two compounds, we extract information on the onset of magnetic correlations at and above the transition temperature in LIO, the bare spin-flip scattering rate in equilibrium, the lifetime of low-lying quasiparticle excitations, and the polarization dependence of optical transitions that are sensitive to magnetic order.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
