In previous work [C. A. Chatzidimitriou-Dreismann et al., J. Chem. Phys. 113, 2784 (2000)] we provided first results of the subfemtosecond dynamics of C–H bond dissociation of solid fully protonated polystyrene at T≈295 K, applying neutron Compton scattering (NCS). A striking anomalous shortfall of the proton scattering intensity with respect to that of the carbon nucleus has been observed. A theoretical explanation based on short-lived protonic quantum entanglement (QE) has also been given. Here we present a twofold extension of that work: Investigation of the found anomaly (i) in solid D-polystyrene with various degrees of aromatic protonation [(-CD2CDC6HxDy-)n with x+y=5] and (ii) in liquid C6H6 and C6H6–C6D6 mixtures. A striking decrease of the neutron cross-section density of H by 20% (on the average) was observed, which appeared to be weakly dependent on the H:D atomic ratio. This result indicates that the considered effect is mainly of intramolecular origin. In contrast to previous NCS experiments on metallic hydrides which revealed a strong scattering time (τscatt) dependence of the decrease of the neutron cross-section density of H, this effect is only slightly apparent in polystyrene and benzene, thus indicating different dynamics of the decoherence process due to different electronic environments. All presented results imply that short-lived QE may be highly relevant for chemical and biological systems.
Although magnetically ordered at low temperatures, the spin-
21 triangular antiferromagnet
Cs2CuCl4 exhibits remarkable spin dynamics that strongly suggest proximity to a spin-liquid phase. Here we ask whether a proximate spin liquid may also occur in an applied magnetic field, leaving a similar imprint on the dynamical spin correlations of this material. Specifically, we explore a spatially anisotropic Heisenberg spin-
21 triangular antiferromagnet at
31 magnetization from a dual vortex perspective, and indeed find a ``critical'' spin-liquid phase described by quantum electrodynamics in
(2+1)-dimensions with an emergent SU(6) symmetry. A number of nontrivial predictions follow for the dynamical spin structure factor in this ``algebraic vortex liquid'' phase, which can be tested via inelastic neutron scattering. We also discuss how well-studied ``up-up-down'' magnetization plateaus can be captured within our approach, and further predict the existence of a stable gapless solid phase in a weakly ordered up-up-down state. Finally, we predict several anomalous ``roton'' minima in the excitation spectrum in the regime of lattice anisotropy where the canted N\'eel state appears.