Charge modulation, spin response, and dual Hofstadter butterfly in high-Tc cuprates

The modulated density of states observed in recent STM experiments in underdoped cuprates is argued to be a manifestation of the charge-density wave of Cooper pairs (CPCDW). CPCDW formation is due to superconducting phase fluctuations enhanced by Mott-Hubbard correlations near half-filling. The physics behind the CPCDW is related to a Hofstadter problem in a dual superconductor. It is shown that CPCDW does not impact nodal fermions at the leading order. An experiment is proposed to probe coupling of the CPCDW to the spin carried by nodal quasiparticles.     

Calculation of coefficients of a cardinal B-spline

It is well known that a cardinal B-spline of order $m,m\in \mathbb{N}$, is a piecewise polynomial function. In this note we propose an effective method for calculating the coefficients of polynomials which constitute a cardinal B-spline.     

Intra- and Intermolecular Rovibrational States of HCl-H\begin{document}$ _\textbf{2} $\end{document}O and DCl-H\begin{document}$ _\textbf{2} $\end{document}O Dimers from Full-Dimensional and Fully Coupled Quantum Calculations

We report full-dimensional and fully coupled quantum bound-state calculations of the \begin{document}$ J $\end{document} = 1 intra- and intermolecular rovibrational states of two isotopologues of the hydrogen chloride-water dimer, HCl-H\begin{document}$ _2 $\end{document}O (HH) and DCl-H\begin{document}$ _2 $\end{document}O (DH). The present study complements our recent theoretical investigations of the \begin{document}$ J $\end{document} = 0 nine-dimensional (9D) vibrational level structure of these and two other H/D isotopologues of this noncovalently bound molecular complex, and employs the same accurate 9D permutation invariant polynomial-neural network potential energy surface. The calculations yield all intramolecular vibrational fundamentals of the HH and DH dimers and the low-energy intermolecular rovibrational states in these intramolecular vibrational manifolds. The results are compared with those of the 9D \begin{document}$ J $\end{document} = 0 calculations of the same dimers. The energy differences between the \begin{document}$ K $\end{document} = 1 and \begin{document}$ K $\end{document} = 0 eigenstates exhibit pronounced variations with the intermolecular rovibrational states, for which a qualitative explanation is provided.     

Assembly of the first fullerene-type metal-organic frameworks using a planar five-fold coordination node

Pump up the volume: Slow crystallization of Na[C(5) (CN)(5) ], the unsolvated sodium salt of pentacyanocyclopentadienide, gives the first example of an anionic coordination network based on metal-fullerene units. The structure of this network is closely related to a type?I gas clathrate in which around 66?% of the unit cell volume is occupied by solvent molecules.     

Quantum criticality of D-wave quasiparticles and superconducting phase fluctuations

We present finite temperature (T) extension of the (2+1)-dimensional QED (QED3) theory of under-doped cuprates. The theory describes nodal quasiparticles whose interactions with quantum proliferated hc/2e vortex-antivortex pairs are represented by an emergent U(1) gauge field. Finite T introduces a scale beyond which the spatial fluctuations of vorticity are suppressed. As a result, the spin susceptibility of the pseudogap state is bounded by T2 at low T and crosses over to approximately T at higher T, while the low-T specific heat scales as T2, reflecting the thermodynamics of QED3. The Wilson ratio vanishes as T-->0; the pseudogap state is a "thermal (semi)metal" but a "spin-charge dielectric." This non-Fermi liquid behavior originates from two general principles: spin correlations induced by "gauge" interactions of quasiparticles and fluctuating vortices and the "relativistic" scaling of the T=0 fixed point.     

Wave function delocalization and large-amplitude vibrations of helium on corrugated aromatic microsurfaces: tetracene.He and pentacene.He van der Waals complexes

We report accurate quantum three-dimensional calculations of highly excited intermolecular vibrational states of the van der Waals (vdW) complexes tetracene.He and pentacene.He in the S1 excited electronic state. The aromatic molecules were taken to be rigid and the intermolecular potential energy surfaces (IPESs) were modeled as a sum of atom-atom Lennard-Jones pair potentials. The IPESs are corrugated in the direction of the long (x) axis of the aromatic molecules, due to the presence of the symmetrically equivalent global double minimum for tetracene.He, and a triple minimum (central global minimum and two equivalent local minima) for pentacene.He, on each side of the aromatic plane. Both IPESs have two additional minor equivalent local minima further away from the center of the molecule. The vdW vibrational states analyzed in this work cover about 80% of the well depths of the IPESs. The mode coupling is generally weak for those states whose out-of-plane (z) mode is unexcited. However, the z-mode fundamental is strongly coupled to the short-axis (y) in-plane mode, so that the pure z-mode excitation could not be identified. The He atom exhibits large in-plane spatial delocalizaton already in the ground vdW vibrational state, which increases rapidly upon the excitation of the in-plane x and y modes, with little hindrance by the corrugation of the aromatic microsurfaces. For the vdW vibrational energies considered, the He atom spatial delocalization reaches Deltax and Deltay values of approximately 5 and 4 A, respectively, and is limited only by the finite size of the aromatic substrates. Side-crossing delocalization of the wave functions on both sides of the molecular plane is found at excitation energies >30 cm(-1), giving rise to the energy splittings of the pairs of states symmetric/antisymmetric with respect to the aromatic plane; the splittings show strong vdW vibrational mode specificity.     

Polysubstituted 5-Phenylazopyrimidines: Extremely Fast Non-ionic Photochromic Oscillators

Photochromic systems with an ultrahigh rate of thermal relaxation are highly desirable for the development of new efficient photochromic oscillators. Based on DFT calculations, we designed a series of 5-phenylazopyrimidines with strong push–pull character in silico and observed very low energy barriers for the thermal (Z)-to-(E) isomerization. The structure of the (Z)-isomer of the slowest isomerizing derivative in the series was confirmed by NMR analysis with in situ irradiation at low temperature. The substituents can tune the lifetime of thermal back isomerization from hundreds of microseconds to several nanoseconds (8 orders of magnitude). The photoswitching parameters were extracted from transient absorption techniques and a dominant rotation mechanism of the (Z)-to-(E) thermal fading was proposed based on DFT calculations.     

Instability of the spiral state of the doped Hubbard model

It is shown that the homogeneous spiral state of the doped Hubbard model is unstable for infinitesimal doping concentration. The spin response about the Hartree-Fock spiral state is evaluated, considering both the interband and intraband processes. Driven by long-wavelength, intraband spin fluctuations, the instability towards infinitesimal fluctuations about the mean-field state is inferred from the nature of the static spin response.     

Molecular topological index: An extension to heterosystems

The molecular topological index (MTI), recently introduced by Schultz, is extended to heterosystems. In order to test the utility of this formulation of the MTI, the index is used to set up the structure-property model for boiling points of alkyl alcohols. This model is comparable to related models based on the connectivity index and on the Wiener index.Dedicated to Professor Frank Harary on the occasion of his 70th birthday.