The spin-orbit assisted Mott insulator \(\alpha\)-RuCl\(_3\) is a prime candidate for material realization of the Kitaev quantum spin liquid. While little attention has been paid to charge degrees of ...freedom, charge effects, such as electric polarization, may arise in this system. Here, we report distortion-induced local electric polarization in \(\alpha\)-RuCl\(_3\) as evidenced by single-crystal X-ray diffraction, second harmonic generation (SHG) and dielectric measurements. The SHG signal appears at room temperature and develops substantially in the Kitaev paramagnetic state when short-range spin correlations come into play. Despite sizable pyroelectric currents in the Kitaev paramagnetic state, the absence of hysteresis in electric field-dependent polariza-tion (P-E) points to the short-range nature of electric polarization. This localized electric polarization is likely the result of distortion-induced charge dimerization, achieved through virtual hopping-induced charge redistribution. In addition, the electric polarization is boosted by short-range spin correlations via spin-phonon coupling in the Kitaev paramagnetic state. Our results emphasize the importance of charge degrees of freedom in \(\alpha\)-RuCl\(_3\), which establish a novel platform to investi-gate charge effects in Kitaev materials.
Phys. Rev. B 96, 121107 (2017) We report magnetotransport study on type-II Weyl semimetal WP$_2$ single
crystals. Magnetoresistance (MR) exhibits a nonsaturating $H^{n}$ field
dependence (14,300\% at ...2 K and 9 T) whereas systematic violation of Kohler's
rule was observed. Quantum oscillations reveal a complex multiband electronic
structure. The cyclotron effective mass close to the mass of free electron
m$_e$ was observed in quantum oscillations along $b$-axis, while reduced
effective mass of about 0.5$m_e$ was observed in $a$-axis quantum oscillations,
suggesting Fermi surface anisotropy. Temperature dependence of the resistivity
shows a large upturn that cannot be explained by the multi-band
magnetoresistance of conventional metals. Even though crystal structure of
WP$_{2}$ is not layered as in transition metal dichalcogenides, quantum
oscillations suggest partial two-dimensional character.
By measuring and comparing δD, δ18O, and3H values of different sections in Lhasa River, we can trace its water resource and water environment. We have concluded that the upper reaches of the Lhasa ...River are mainly supplied by melt-water (with lower3H value and mineralization degree) and underground water (with lower3H value and higher mineralization degree). The middle reaches are mainly supplied by rainwater (with higher3H value and mineralization degree).
We report magnetotransport properties of BaZnBi\(_{2}\) single crystals. Whereas electronic structure features Dirac states, such states are removed from the Fermi level by spin-orbit coupling (SOC) ...and consequently electronic transport is dominated by the small hole and electron pockets. Our results are consistent with three dimensional (3D) but also with quasi two dimensional (2D) portions of the Fermi surface. The spin-orbit coupling-induced gap in Dirac states is much larger when compared to isostructural SrMnBi\(_{2}\). This suggests that not only long range magnetic order but also mass of the alkaline earth atoms A in ABX\(_{2}\) (A = alkaine earth, B = transition metal and X=Bi/Sb) are important for the presence of low-energy states obeying the relativistic Dirac equation at the Fermi surface
We report electrical and thermal transport properties of single crystalline kagome metals \(A\)Ti\(_3\)Bi\(_5\) (\(A\) = Rb, Cs). Different from the structural similar kagome superconductors ...\(A\)V\(_3\)Sb\(_5\), no charge density wave instabilities are found in \(A\)Ti\(_3\)Bi\(_5\). At low temperatures below 5 K, signatures of superconductivity appear in \(A\)Ti\(_3\)Bi\(_5\) as seen in magnetization measurements. However, bulk superconductivity is not evidenced by specific heat results. Similar to \(A\)V\(_3\)Sb\(_5\), \(A\)Ti\(_3\)Bi\(_5\) show nonlinear magnetic field dependence of the Hall effect below about 70 K, pointing to a multiband nature. Unlike \(A\)V\(_3\)Sb\(_5\) in which phonons and electron-phonon coupling play important roles in thermal transport, the thermal conductivity in \(A\)Ti\(_3\)Bi\(_5\) is dominated by electronic contributions. Moreover, our calculated electronic structure suggests that van Hove singularities are sitting well above the Fermi energy. Compared with \(A\)V\(_3\)Sb\(_5\), the absence of charge orders in \(A\)Ti\(_3\)Bi\(_5\) is closely associated with minor contributions from electron-phonon coupling and/or van Hove singularities.
High-tech industry zone play a important role in the global economic system with the continuously new knowledge innovation, itpsilas becoming the main motion of regional economic structure ...optimization and competition. The technology ability and diffuse effect of High-tech zone influence itself and regional economic development greatly. This paper design High-tech zone technology innovation ability appraisal index system, and take integrated appraisal with BP neural network, a improved method is put forward to identification mode by Euclidean distance, and appraise a true sample with it.
Connections between crystal chemistry and critical temperature \(T_c\) have been in the focus of superconductivity, one of the most widely studied phenomena in physics, chemistry and materials ...science alike. In most Fe-based superconductors, materials chemistry and physics conspire so that \(T_c\) correlates with the average anion height above the Fe plane, i. e. with the geometry of the FeAs4 or FeCh4 (Ch = Te, Se, or S) tetrahedron. By synthesizing Fe\(_{1-y}\)Se\(_{1-x}\)S\(_x\) (0$\leq$$x$$\leq\(1, \)y$$\leq\(0.1), we find that in alloyed crystals \)T_c\( is not correlated with the anion height like it is for most other Fe superconductors. Instead, changes in \)T_c\((\)x\() and tetragonal-to-orthorombic (nematic) transition \)T_s\((\)x\() upon cooling are correlated with disorder in Fe vibrations in the direction orthogonal to Fe planes, along the crystallographic c-axis. The disorder stems from the random nature of S substitution, causing deformed Fe(Se,S)4 tetrahedra with different Fe-Se and Fe-S bond distances. Our results provide evidence of \)T_c\( and \)T_s$ suppression by disorder in anion height. The connection to local crystal chemistry may be exploited in computational prediction of new superconducting materials with Fe/S building blocks.
Layered van der Waals (vdW) magnets are prominent playgrounds for developing magnetoelectric, magneto-optic and spintronic devices. In spintronics, particularly in spincaloritronic applications, low ...thermal conductivity (\(\kappa\)) is highly desired. Here, by combining thermal transport measurements with density functional theory calculations, we demonstrate low \(\kappa\) down to 1 W m\(^{-1}\) K\(^{-1}\) in a typical vdW ferromagnet Cr\(_2\)Si\(_2\)Te\(_6\). In the paramagnetic state, development of magnetic fluctuations way above \(T_\mathrm{c}=\) 33 K strongly reduces \(\kappa\) via spin-phonon scattering, leading to low \(\kappa \sim\) 1 W m\(^{-1}\) K\(^{-1}\) over a wide temperature range, in comparable to that of amorphous silica. In the magnetically ordered state, emergence of resonant magnon-phonon scattering limits \(\kappa\) below \(\sim\) 2 W m\(^{-1}\) K\(^{-1}\), which would be three times larger if magnetic scatterings were absent. Application of magnetic fields strongly suppresses the spin-phonon scattering, giving rise to large enhancements of \(\kappa\). Our calculations well capture these complex behaviours of \(\kappa\) by taking the temperature- and magnetic-field-dependent spin-phonon scattering into account. Realization of low \(\kappa\) which is easily tunable by magnetic fields in Cr\(_2\)Si\(_2\)Te\(_6\), may further promote spincaloritronic applications of vdW magnets. Our theoretical approach may also provide a generic understanding of spin-phonon scattering, which appears to play important roles in various systems.
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