Investigations of proximity-induced superconductivity in the topological insulator Bi2Te3 by microRaman spectroscopy.

We used the topological insulator (TI) Bi2Te3 and a high-temperature superconductor (HTSC) hybrid device for investigations of proximity-induced superconductivity (PS) in the TI. Application of the superconductor YBa2Cu3O7-δ (YBCO) enabled us to access higher temperature and energy scales for this phenomenon. The HTSC in the hybrid device exhibits emergence of a pseudogap state for T > Tc that converts into a superconducting state with a reduced gap for T < Tc. The conversion process has been reflected in Raman spectra collected from the TI. Complementary charge transport experiments revealed emergence of the proximity-induced superconducting gap in the TI and the reduced superconducting gap in the HTSC, but no signature of the pseudogap. This allowed us to conclude that Raman spectroscopy reveals formation of the pseudogap state but cannot distinguish the proximity-induced superconducting state in the TI from the superconducting state in the HTSC characterised by the reduced gap. Results of our experiments have shown that Raman spectroscopy is a complementary technique to classic charge transport experiments and is a powerful tool for investigation of the proximity-induced superconductivity in the Bi2Te3.

Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi2Te3 heterostructure studied by high resolution Brillouin spectroscopy.

The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm-1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm-1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models.

The electron-phonon interaction at deep Bi 2 Te3-semiconductor interfaces from Brillouin light scattering.

It is shown that the electron-phonon interaction at a conducting interface between a topological insulator thin film and a semiconductor substrate can be directly probed by means of high-resolution Brillouin light scattering (BLS). The observation of Kohn anomalies in the surface phonon dispersion curves of a 50 nm thick Bi2Te3 film on GaAs, besides demonstrating important electron-phonon coupling effects in the GHz frequency domain, shows that information on deep interface electrons can be obtained by tuning the penetration depth of optically-generated surface phonons so as to selectively probe the interface region, as in a sort of quantum sonar.

Landau model for the elastic properties of the ferroelastic crystal Rb(4)LiH(3)(SO(4))(4).

Using sound velocity measurements, we report a detailed investigation of the elastic properties of Rb(4)LiH(3)(SO(4))(4) realized as a function of temperature and pressure. Results are compared to predictions of a phenomenological Landau model. Supported by recent Raman scattering measurements, we assume that the [Formula: see text] structural transformation observed at T(c) = 134 K corresponds to a pseudo-proper ferroelastic transition. For the numerical analysis, all coupling parameters are determined using the temperature dependence of the frequency of the soft optical B mode, the temperature dependence of spontaneous strains, and the pressure dependence dT(c)/dP = 191 ± 2 K GPa(-1) also determined in this work. Our comparison indicates that the [Formula: see text] structural transition in Rb(4)LiH(3)(SO(4))(4) is fully consistent with predictions derived using our pseudo-proper ferroelastic model. Thus, all data presented in this paper corroborate that the mechanism leading to the structural transition at T(c) = 134 K results from the softening of the B optical mode observed at 31 cm(-1). This detailed analysis also refutes the idea that Rb(4)LiH(3)(SO(4))(4) shows incomplete softening of the soft acoustic mode also associated with that structural transition.

Bond selective dissociative electron attachment to thymine.

Free-electron attachment to thymine and partially deuterated thymine, where D replaces H at all carbon atoms, is studied in the electron energy range from about 0 to 15 eV. The formation of fragment anions that are formed by the loss of one or two H (D) atoms is analyzed as a function of the incident electron energy using a crossed electron/neutral beam apparatus in combination with a quadrupole mass spectrometer. By using partially deuterated thymine and quantum-chemical calculation a bond selectivity for the loss of one and two hydrogen atoms is observed that is determined only by the kinetic energy of the incident electron.

Hemoptysis as the presenting symptom in bronchiolitis obliterans organizing pneumonia.

Bronchiolitis obliterans organizing pneumonia (BOOP) is an uncommon but increasingly recognized pulmonary entity that usually presents with symptoms of dyspnea, cough, and fever. The medical literature describes rare cases of hemoptysis in BOOP, with very small quantities of blood expectorated. We describe two cases of BOOP, one idiopathic and one in association with rheumatoid arthritis, in which large-quantity hemoptysis was the primary presenting symptom.