Maximally localized Wannier function within linear combination of pseudo-atomic orbital method: Implementation and applications to transition-metal-benzene complex

Construction of maximally localized Wannier functions (MLWFs) has been implemented within the linear combination of pseudo-atomic orbital (LCPAO) method. Detailed analysis using MLWFs is applied to three closely related materials, single benzene (Bz) molecule, organometallic Vanadium-Bz infinite chain, and V$_2$Bz$_{3}$ sandwich cluster. Two important results come out from the present analysis: 1) for the infinite chain, the validity of the basic assumption in the mechanism of Kanamori and Terakura for the ferromagnetic (FM) state stability is confirmed; 2) for V$_2$Bz$_3$, an important role played by the difference in the orbital energy between the edge Bzs and the middle Bz is newly revealed: the on-site energy of p$\delta$ states of edge Bzs is higher than that of middle Bz, which further reduces the FM stability of V$_2$Bz$_3$.Comment: 19 pages and 5 figure

Antiferromagnetism and Superconductivity in UPt_3

The short ranged antiferromagnetism recently seen in UPt_3 is proved incompatible with two dimensional (2D) order parameter models that take the antiferromagnetism as a symmetry breaking field. To adjust to the local moment direction, the order parameter twists over very long length scales as per the Imry-Ma argument. A variational solution to the Ginzburg-Landau equations is used to study the nature of the short ranged order. Although there are still two transitions, the lower one is of first order -- in contradiction to experiments. It is shown that the latent heat predicted by the 2D models at the lower transition is too large not to have been seen. A simple periodic model is numerically studied to show that the lower transition can not be a crossover either.Comment: To appear in Journal of Physics: Condensed Matter. 9 pages, 2 figure

Three-dimensional crystal orientation of blue phase liquid crystals on surfaces

SPIE Organic Photonics + Electronics, 2018, San Diego, California, United StatesH. Yoshida, M. Takahashi, T. Ohkawa, J.-i. Fukuda, H. Kikuchi, and M. Ozaki "Three-dimensional crystal orientation of blue phase liquid crystals on surfaces", Proc. SPIE 10735, Liquid Crystals XXII, 107350I (14 September 2018). https://doi.org/10.1117/12.232315

Krylov Subspace Method for Molecular Dynamics Simulation based on Large-Scale Electronic Structure Theory

For large scale electronic structure calculation, the Krylov subspace method is introduced to calculate the one-body density matrix instead of the eigenstates of given Hamiltonian. This method provides an efficient way to extract the essential character of the Hamiltonian within a limited number of basis set. Its validation is confirmed by the convergence property of the density matrix within the subspace. The following quantities are calculated; energy, force, density of states, and energy spectrum. Molecular dynamics simulation of Si(001) surface reconstruction is examined as an example, and the results reproduce the mechanism of asymmetric surface dimer.Comment: 7 pages, 3 figures; corrected typos; to be published in Journal of the Phys. Soc. of Japa

Simultaneous ground-based and satellite observations of natural VLF waves in Antarctica: A case study of downward ionospheric penetration of whistler-mode waves

AbstractTo investigate downward ionospheric-penetration characteristics of VLF (several hundred Hz to 17.8 kHz) whistler-mode waves, we conducted simultaneous observations (in 2006) of natural VLF waves using both ground stations in Antarctica and the Japanese Akebono satellite. The ground-based and satellite observations included an interesting event for which both observed similar VLF waves. In this study, we theoretically calculate down-going whistler-mode wave propagation based on ground-satellite observations using the full-wave analysis. In a case study, the observed wave-normal angles were approximately 140–160 degrees for a dayside chorus event on 15 March 2006. The theoretical calculation showed that the wave-normal angles for ionospheric penetration should be around 155.6 degrees, with its angular width of approximately 2 degrees. Moreover, the wave-energy loss due to ionospheric penetration is estimated at 20.4 dB based on our theoretical calculation, in accordance with the observed 17–19 dB

Characterization of halogen-bridged binuclear metal complexes as hybridized two-band materials

We study the electronic structure of halogen-bridged binuclear metal (MMX) complexes with a two-band Peierls-Hubbard model. Based on a symmetry argument, various density-wave states are derived and characterized. The ground-state phase diagram is drawn within the Hartree-Fock approximation, while the thermal behavior is investigated using a quantum Monte Carlo method. All the calculations conclude that a typical MMX compound Pt_2(CH_3CS_2)_4I should indeed be regarded as a d-p-hybridized two-band material, where the oxidation of the halogen ions must be observed even in the ground state, whereas another MMX family (NH_4)_4[Pt_2(P_2O_5H_2)_4X] may be treated as single-band materials.Comment: 16 pages, 11 figures embedded, to be published in Phys. Rev.

Polar type density of states in non-unitary odd-parity superconducting states of gap with point nodes

It is shown that the density of states (DOS) proportional to the excitation energy, the so-called polar like DOS, can arise in the odd-parity states with the superconducting gap vanishing at points even if the spin-orbit interaction for Cooper pairing is strong enough. Such gap stuructures are realized in the non-unitary states, F_{1u}(1,i,0), F_{1u}(1,varepsilon,varepsilon^{2}), and F_{2u}(1,i,0), classified by Volovik and Gorkov, Sov. Phys.-JETP Vol.61 (1985) 843. This is due to the fact that the gap vanishes in quadratic manner around the point on the Fermi surface. It is also shown that the region of quadratic energy dependence of DOS, in the state F_{2u}(1,varepsilon,varepsilon^{2}), is restricted in very small energy region making it difficult to distinguish from the polar-like DOS.Comment: 5 pages, 3 figures, submitted to J. Phys.: Condens. Matter Lette

Separate measurements of the flexoelectric and surface polarization in a model nematic liquid crystal p-methoxybenzylidene-p´-butylaniline : Validity of the quadrupolar approach

The temperature dependences of the surface polarization have been measured at the interface of a conductive glass with both the homogeneously and homeotropically oriented nematic liquid crystal p-methoxybenzylidene-p´-butylaniline. The polarization was found in the field-off regime from the pyroelectric response of a cell to a short laser pulse, absorbed in the bulk of the liquid crystal. The temperature increment was calculated from the measurements of the birefringence induced by the same light pulse. It has been shown that the surface polarization at the homeotropic (mh) and planar (mp) interfaces is directed from an interface into the bulk and from the bulk to an interface, respectively (with a magnitude mh~— 0.3 pC/m and mp' ≈ 0.2 pC/m at 25℃). The experimental data may be explained in terms of the quadrupole model of the order-electric polarization with account of some additional contribution from molecular dipoles. The same technique also allows for the measurements of the z component of the flexoelectric polarization using a pyroelectric response of a hybrid (homeoplanar) aligned nematic cell and proper subtracting of the surface contributions. The flexoelectric polarization has been shown to be opposite to the sum of the surface terms mh + mp and directed from the planar to homeotropic interface. This means that the sum of the flexoelectric coefficients e=(e1 + e3) is positive (e ≅ 1.7 pC/m at 28℃). The temperature dependence of e has been shown to involve a combination of both the quadrupolar and dipolar contributions