Modern Physics Letters B

Biophoton emission is a general phenomenon of living systems. It concerns a weak photon radiation from a few to some hundred photons per second, per square centimeter surface area, at least within the spectral region from 200 to 800 nm. The results indicate that biophoton emission can be assigned to a coherent field within living organisms, its functions being intra and intercellular regulation and communication. This review deals with some central results and their interpretation.

The structural, electronic, magnetic, and optical properties of AuAl₂, AuGa₂, AuIn₂, and PtGa₂ are reviewed. These experimental results are compared with the values of the density of states at the Fermi level derived from band-structure calculations. The so-called “AuGa₂ dilemma” and the controversial positions of the Au 5d bands in AuAl₂, AuGa₂, and AuIn₂ are discussed. The physical properties of PtGa₂ are summarized and compared with those of the Au intermetallic compounds. Recent researches on the growth and characterization of these compounds in thin-film form are also presented.

We review recent work clarifying the sense in which the Jahn-Teller effect can exist in a molecular complex in liquid solution. We review the molecular dynamics methods for modeling such liquid systems using the cupric ion in aqueous solution as an example. We review the experimental evidence for the Jahn-Teller effect in liquids, emphasizing the importance of taking the time scale of the measurement into account. Finally we discuss the role of quantum coherence and the Berry phase in the Jahn-Teller effect.

A model for crack propagation is proposed that reproduces, for the first time, the morphological transitions of cracks in the quenched glass plate recently observed by Yuse and Sano [Nature362, 329 (1993)].

We consider the effect of dissipation on the nonlinear mobility in a superconducting tunnel junction. Using a variational approach, the critical mobility crucially depends on the coupling to the ohmic bath. At ultrasmall capacitances, good agreement is found with decay rates diagrams. The current model could be developed in other contexts, such as that of a ferroelectric capacitor, as proposed by Widom and Clark (Phys. Rev.B30, 1205 (1984)).

A new saddle point state is proposed for the lightly doped t-J model in both one-dimensional (1D) and two-dimensional (2D) cases. It is shown that in 2D a long range antiferromagnetic (AF) order is recovered in the zero-doping limit, while in the same limit the well-known power law spin-spin correlation can also be obtained in 1D. At finite doping, interesting properties for both dimensions are exhibited in this new saddle point state, known as the flux binding state.

After a brief description of the K state phenomenon in short-range-ordered substitutional alloys, it is shown that this effect also exists in an interstitial alloy β-PdH(D)_0.63, whose low-temperature resistivity decreases after a quench across the order-disorder transition region around 50 K and/or after electron irradiation.

An empirical “J_c expectation rule” has been devised for YBCO thin films (1000–8000 Å) deposited on various substrates by MOCVD and laser ablation techniques. The “rule” is based on a normal state parameter M defined as the ratio of ΔR/ΔT and R/T, and directly predicts J_c from resistivity measurements. The parameter also serves to delineate three general regions of J_c behavior that are proposed to be linked to film characteristics.

A new method using Fock space wave functions is proposed for studying resonant tunneling in semiconductor quantum wells. The use of binary occupation numbers as dynamical variables, rather than properties of individual electrons, manifestly takes account of electron statistics, which enables investigation of the influence of the Pauli principle on resonant tunneling in the presence of inelastic scattering. Applied to the evaluation of the resonant current in semiconductor heterostructures, our approach predicts considerable deviations from the one-electron and rate equations pictures.

We discuss a limiting procedure for solving for the electronic states in the standard tight-binding model of electrons in a CuO₂ plane, in which all contributions O(t²/U) are retained while all higher order terms are rejected. This limiting process yields the exact results in strong coupling, and uncovers a variety of quasiparticles: fermions with and without dispersion, localized spin-1 triplets, their interactions, but no superconductivity. In this paper we fill in some minor details and give a lower bound to the ground state energy valid at all ratios of t/U. We discuss the dynamic process by which two triplets can annihilate, and show that their lifetime is inversely proportional to their energy.