Bcc 4^4He as a Coherent Quantum Solid

In this work we investigate implications of the quantum nature of bcc $^{4}$% He. We show that it is a unique solid phase with both a lattice structure and an Off-Diagonal Long Range Order of coherently oscillating local electric dipole moments. These dipoles arise from the local motion of the atoms in the crystal potential well, and oscillate in synchrony to reduce the dipolar interaction energy. The dipolar ground-state is therefore found to be a coherent state with a well defined global phase and a three-component complex order parameter. The condensation energy of the dipoles in the bcc phase stabilizes it over the hcp phase at finite temperatures. We further show that there can be fermionic excitations of this ground-state and predict that they form an optical-like branch in the (110) direction. A comparison with 'super-solid' models is also discussed.Comment: 12 pages, 8 figure

Synthetic approaches to artificial photosynthesis: general discussion

Metals in Catalysis, Biomimetics & Inorganic Material

FREQUENCY AND TEMPERATURE DEPENDENCE OF IH NMR OF TRANS-(CH)x

Nous avons étudié la dépendance en température (0,3K < T < 4,2K) et en fréquence (23MHz < f < 35MHz) du temps de relaxation spin-lattice TI des protons dans le composé trans-(CH)x. A 4,2K, nos résultats concordent avec ceux obtenus par Nechtschein et al. Quand l'échantillon est refroidi, TI s'allonge, et T-II=αf-1/2-β, où α et β sont des fonctions de la température. TI peut aussi être exprimé par TI= A exp(-Ɗ/T), où Ɗ = γH est l'énergie d'activation (et A et γ sont des constantes). Nous observons un facteur g égal à 3,3 pour l'énergie d'activation, ce qui suggère que nous sommes dans la limite de basses températures de la diffusion I-D de spins nucléaires tel que Clark et al. l'ont indiqué.We have carried out a study of the temperature (0.3K < T < 4.2K) and frequency (23MHz < f < 35MHz) dependence of the proton spin lattice relaxation time, TI, of trans-(CH)x. The data at 4.2K are in agreement with earlier measurements of Nechtschein et al. As the sample is cooled, TI continues to increase, with T-II=α f-1/2-β), where α and β are temperature dependent quantities. Alternately TI is expressed as an activated quantity, TI = A exp(- Ɗ/T), with Ɗ = γH (A and γ constant). The observed g factor of 3.3 for the activation energy suggests that we are in the low temperature limit for I-D nuclear spin diffusion as discussed by Clark et al