K.H. Bennemann

Soliton-like processes during right-left transition in DNA

Abstract A salt induced right-left conformational change in DNA is discussed. A phenomenological model is presented for the transition in short DNAs. For long DNAs. For long DNAs, a microscopic model equation of motion is analyzed. Solitary-waves solutions are demonstrated and some experimental implications are emphasized.

Analysis of the anomoulos ultrasonic attenuation in the heavy-fermion metal UPt3

Abstract Using the Boltzmann equiation, we determine the sound attenuation Γ , in particular the contribution ΔΓ arising from heat conduction. We show that in constrast to normal metals this contribution is significant or heavy-fermion metals with large Gruneisen constant Ω and responsible for the anomalous temperature dependence of Γ observed recently at lopw temperature for UPt 3 . Since ΔΓ ∝ Ω 2 , an anomalous temperature dependence pf Ω(T) is mirrored in Λ ( T ). We present results for Ω(T) .

On the valence change at the surface of samarium

Abstract Within a model previously used to investigate the mixed valence transition in rare-earth compounds we show that the samarium ions at the surface are most probably in a divalent state.

On the doping induced gap states of high-Tc oxides due to oxygen disorder

Abstract The photoemission and inverse photoemission spectra clearly show doping induced states inside the antiferromagnetic gap of high- T c superconducting oxides. Experimental data indicate that these states have dominant oxygen character and result from the transfer of density of states from the lower and upper Hubbard bands. They also seem to be related to localized orbitals. It is important to determine the physical nature of these states and whether these states in the gap result solely from strong correlations or from a combination of strong correlation and oxygen disorder. We show in this paper that structural defects like excess oxygen and oxygen vacancies in the CuO 2 plane will cause deep impurity states in the gap and which have approximately the observed characteristics. Furthermore, we find that copper disorder does not cause such states in the gap. Despite its simplicity these results are interesting with regard to clarifying the physical origin of these states.

Equilibrium polymerization in two dimensions

Abstract A mean-field theory of equilibrium polymerization on a square lattice is presented. A novel feature of the model is the treatment of the whole range of rigidity of polymers (from flexible to stiff) as well as a simultaneous account of both polymer rings and excluded volume. As a result a line of tricritical points is found.

On high Tc superconductivity in La2CuO4-type compounds

Abstract Important electronic parameters and phonon frequencies are estimated for La 2− x M x CuO 4 systems. The hybridized p-d states of copper and oxygen give rise to large frequency modes of the CuO 6 octahedron. We estimate 〈 h ω ph 〉 ∼ 0.05 eV, N (0) ∼ 1 state/ eV cell spin, λ ≤1, and thus T c ∼ 28 K due to electron-phonon coupling. No large phonon softening occurs due to electron correlations. An isotope effect is expected.

Equilibrium polymerization of stiff polymers

Equilibrium polymerization of stiff polymers is considered in a meanfield approximation. It is shown that polymerization is of order-disorder type. The phase diagram exhibits a critical line which is replaced at tricritical point,by a discontinuity line. It is also found that polymer weight fraction is non-zero at both sides of the transition showing only a mild singularity (∼‖T-Tc‖) at continuous transition.

Stochastic approach to electron lattice system in one dimension

Abstract The one dimensional electron lattice problem is studied using Dysons approach to 1d glasses. For the extreme narrow band case an exact solution is found.

Liquid metals and alloys in the tight-binding model

Abstract Self consistent single site expressions are derived for the electronic density of liquid metals and liquid alloys in the tight-binding approximation.