Magneto-Roton Modes of the Ultra Quantum Crystal: Numerical Study

The Field Induced Spin Density Wave phases observed in quasi-one-dimensional conductors of the Bechgaard salts family under magnetic field exhibit both Spin Density Wave order and a Quantized Hall Effect, which may exhibit sign reversals. The original nature of the condensed phases is evidenced by the collective mode spectrum. Besides the Goldstone modes, a quasi periodic structure of Magneto-Roton modes, predicted to exist for a monotonic sequence of Hall Quantum numbers, is confirmed, and a second mode is shown to exist within the single particle gap. We present numerical estimates of the Magneto-Roton mode energies in a generic case of the monotonic sequence. The mass anisotropy of the collective mode is calculated. We show how differently the MR spectrum evolves with magnetic field at low and high fields. The collective mode spectrum should have specific features, in the sign reversed "Ribault Phase", as compared to modes of the majority sign phases. We investigate numerically the collective mode in the Ribault Phase.Comment: this paper incorporates material contained in a previous cond-mat preprint cond-mat/9709210, but cannot be described as a replaced version, because it contains a significant amount of new material dealing with the instability line and with the topic of Ribault Phases. It contains 13 figures (.ps files

On the self-similarity in quantum Hall systems

The Hall-resistance curve of a two-dimensional electron system in the presence of a strong perpendicular magnetic field is an example of self-similarity. It reveals plateaus at low temperatures and has a fractal structure. We show that this fractal structure emerges naturally in the Hamiltonian formulation of composite fermions. After a set of transformations on the electronic model, we show that the model, which describes interacting composite fermions in a partially filled energy level, is self-similar. This mathematical property allows for the construction of a basis of higher generations of composite fermions. The collective-excitation dispersion of the recently observed 4/11 fractional-quantum-Hall state is discussed within the present formalism.Comment: 7 pages, 4 figures; version accepted for publication in Europhys. Lett., new version contains energy calculations for collective excitations of the 4/11 stat

Crustal Thickening, Partial Melting, and Strain Localization: Insights from the Leo Pargil dome, NW India

Abstract HKT-ISTP 2013 A

An alternative search for the electron capture of Te-123

A search for the electron capture of Te-123 has been performed using CdZnTe detectors. After a measuring time of 195 h no signal could be found resulting in a lower half-life limt of $T_{1/2} > 3.2 \cdot 10^{16}$ yrs (95 % CL) for this process. This clearly discriminates between existing experimental results which differ by six orders of magnitude and our data are in strong favour of the result with longer half-lifes.Comment: 2 pages, 2 eps-figures, reanalysis of data set

Optical absorption measurements of silica containing Si nanocrystals produced by ion implantation and thermal annealing

Optical absorption spectra from silicon-implanted silica slides are shown to contain features due to optical interference. These features, which result from the modified refractive index profile produced by the implant, can readily lead to misinterpretation of absorption spectra. To demonstrate the importance of such effects, silica samples were implanted with 80, 400, and 600 keV Si ions to fluences in the range 0.6–3.0×10¹⁷ Si.cm⁻² and annealed at 1100 °C for 1 h to form Si nanocrystals. Optical absorption/transmittance spectra from these samples show considerable structure that is characteristic of the particular implant conditions. This structure is shown to correlate with the transmittance of the samples as calculated from the modified refractive index profile for each implant. The lack of such structure in absorption spectra measured by photodeflection spectrometry is used to confirm this interpretation

Ultrafast trapping times in ion implanted InP

As⁺ and P⁺implantation was performed on semi-insulating (SI) and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1×10¹⁶ cm⁻² and p-type InP was implanted with doses between 1×10¹² and 1×10¹⁶ cm⁻². Subsequently, rapid thermal annealing at temperatures between 400 and 700 °C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implantedp-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity

Emission of gamma rays shifted from resonant absorption by electron-nuclear double transitions in ^{151}Eu^{2+}:CaF_2

We show that the emission of a gamma-ray photon by a nucleus can be influenced by a microwave magnetic field acting on the atomic electrons. We study theoretically these electron-nuclear double transitions (ENDTs) for ^{151}Eu nuclei in a CaF_2 lattice at low temperature, in the presence of a static magnetic field and of a microwave magnetic field. The ENDTs acquire a significant intensity for certain resonance frequencies. The ENDTs are of interest for the identification of the position of the lines in complex M\"{o}ssbauer spectra.Comment: 8 pages; 3 Postscript figures: Fig. 1, Fig. 2(a), Fig. 2(b

Multicentric Castleman's disease as a cause for unclear febrile episodes in a 55-year-old HIV-infected man

Our case illustrates the difficulties involved in diagnosing multicentric Castleman's disease (MCD) in a human immunodeficiency virus-infected man with febrile episodes and malaise. In the absence of well-established treatment protocols, we have chosen a new treatment algorithm with rituximab, etoposide, and valganciclovir, which led to the remission of clinical symptoms. Yet, we advocate focused exploration for MCD in immunosuppressed patients with unclear febrile episodes, as recent advances in treatment are promisin

Self-energy corrections to anisotropic Fermi surfaces

The electron-electron interactions affect the low-energy excitations of an electronic system and induce deformations of the Fermi surface. These effects are especially important in anisotropic materials with strong correlations, such as copper oxides superconductors or ruthenates. Here we analyze the deformations produced by electronic correlations in the Fermi surface of anisotropic two-dimensional systems, treating the regular and singular regions of the Fermi surface on the same footing. Simple analytical expressions are obtained for the corrections, based on local features of the Fermi surface. It is shown that, even for weak local interactions, the behavior of the self-energy is non trivial, showing a momentum dependence and a self-consistent interplay with the Fermi surface topology. Results are compared to experimental observations and to other theoretical results.Comment: 13 pages, 10 figure