Muon spin relaxation and susceptibility studies of the pure and diluted spin 1/2 kagomé-like lattice system (CuxZn(1-x))3V2O7(OH2) 2H2O

Muon spin relaxation and magnetic susceptibility measurements have been performed on the pure and diluted spin 1/2 kagomé system (CuxZn(1-x))3V2O7(OH)2 2H2O. In the pure x=1 system we found a slowing down of Cu spin fluctuations with decreasing temperature towards T approximately 1 K, followed by slow and nearly temperature-independent spin fluctuations persisting down to T=50 mK, indicative of quantum fluctuations. No indication of static spin freezing was detected in either of the pure (x=1.0) or diluted samples. The observed magnitude of fluctuating fields indicates that the slow spin fluctuations represent an intrinsic property of kagomé network rather than impurity spins.     

Formation and annihilation of laser light pulse quanta in a thermodynamic-like pathway

We present a theoretical and experimental study of multiple pulse formation in passively mode-locked lasers. Following a statistical-mechanics approach, the study yields a thermodynamic-like "phase diagram" with boundaries representing cascaded first order phase transitions. They correspond to abrupt creation or annihilation of pulses and a quantized rf power behavior, as system parameters (noise and/or pumping levels) are varied, in excellent accordance with the experiments. Remarkably, individual pulses carry an almost constant quantum of energy.     

Crossover from dilute to majority spin freezing in two leg ladder system Sr(Cu,Zn)2O3

The two-dimensional electron gas (2DEG) in moderate magnetic fields in ultraclean AlAs-GaAs heterojunctions exhibits transport anomalies suggestive of a compressible anisotropic metallic state. Using scaling arguments and Monte Carlo simulations, we develop an order parameter theory of an electron nematic phase. The observed temperature dependence of the resistivity anisotropy behaves like the orientational order parameter if the transition to the nematic state occurs at a finite temperature T(c) approximately 65 mK, and is slightly rounded by a small background microscopic anisotropy. We propose a light scattering experiment to measure the critical susceptibility.     

The isotopic composition of evaporating waters - review of the historical evolution leading up to the Craig-Gordon model

Attempts to explain the variations in the abundance of heavy isotopic species of water throughout the hydrologic cycle solely by means of the classical equilibrium-fractionation processes could not be reconciled with measured abundances of the isotopic species in residues of "evaporation systems". Focusing on the evaporation of surface waters, the paper follows the evolution of the concepts during the 1950-ties and early 1960-ties leading up to the formulation of the Craig-Gordan Evaporation Model in 1965.     

Hydrodynamic Lyapunov Modes in Translation-Invariant Systems

We study the implications of translation invariance on the tangent dynamics of extended dynamical systems, within a random matrix approximation. In a model system, we show the existence of hydrodynamic modes in the slowly growing part of the Lyapunov spectrum, which are analogous to the hydrodynamic modes discovered numerically by Dellago, Posch, and Hoover. The hydrodynamic Lyapunov vectors lose the typical random structure and exhibit instead the structure of weakly perturbed coherent long-wavelength waves. We show further that the amplitude of the perturbations vanishes in the thermodynamic limit, and that the associated Lyapunov exponents are universal.     

THE ORIGIN OF THE RED-SHIFTED ABSORPTION MAXIMUM OF THE M412 INTERMEDIATE IN THE BACTERIORHODOPSIN PHOTOCYCLE

The factors that red shift the absorption maximum of the retinal Schiff base chromophore in the M₄₁₂ intermediate of bacteriorhodopsin photocycle relative to absorption in solution were investigated using a series of artificial pigments and studies of model compounds in solution. The artificial pigments derived from retinal analogs that perturb chromophore-protein interactions in the vicinity of the ring moiety indicate that a considerable part of the red shift may originate from interactions in the vicinity of the Schiff base linkage. Studies with model compounds revealed that hydrogen bonding to the Schiff base moiety can significantly red shift the absorption maximum. Furthermore, it was demonstrated that although s-trans ring-chain planarity prevails in the M₄₁₂ intermediate it does not contribute significantly (only ca 750 cm⁻¹) to the opsin shift observed in M₄₁₂. It is suggested that in M₄₁₂, the Schiff base linkage is hydrogen bonded to bound water and/or protein residues inducing a considerable red shift in the absorption maximum of the retinal chromophore.     

Semiclassics for Particles with Spin via a Wigner–Weyl-Type Calculus

We show how to relate the full quantum dynamics of a spin-½ particle on \({\mathbb{R}^d}\) to a classical Hamiltonian dynamics on the enlarged phase space \({\mathbb{R}^{2d} \times \mathbb{S}^{2}}\) up to errors of second order in the semiclassical parameter. This is done via an Egorov-type theorem for normal Wigner–Weyl calculus for \({\mathbb{R}^d}\) (Folland, Harmonic Analysis on Phase Space, 1989; Lein, Weyl Quantization and Semiclassics, 2010) combined with the Stratonovich–Weyl calculus for SU(2) (Varilly and Gracia-Bondia, Ann Phys 190:107–148, 1989). For a specific class of Hamiltonians, including the Rabi- and Jaynes–Cummings model, we prove an Egorov theorem for times much longer than the semiclassical time scale. We illustrate the approach for a simple model of the Stern–Gerlach experiment.