Pressure dependence of raman modes in double wall carbon nanotubes filled with 1D tellurium

The preparation of highly anisotropic one-dimensional (1D) structures confined into carbon nanotubes (CNTs) in general is a key objective in nanoscience. In this work, capillary effect was used to fill double wall carbon nanotubes (DWCNTs) with trigonal Tellurium. The samples are characterized by high resolution transmission electronic microscopy and Raman spectroscopy. In order to investigate their structural stability and unravel the differences induced by intershell interactions, unpolarized Raman spectra of radial and tangential modes of DWCNTs filled with 1D nanocrystalline Te excited with 514 nm were studied at room temperature and high pressure. Up to 11 GPa we found a pressure coefficient of 3.7 cm−1 GPa−1 for the internal tube and 7 cm−1 GPa−1 for the external tube. In addition, the tangential band of the external and internal tubes broaden and decrease in amplitude. All findings lead to the conclusion that the outer tube acts as a protection shield for the inner tube (at least up 11 GPa). No pressure-induced structural phase transition was observed in the studied range

Trigonal field acting at the Cr3+ 2 E states in ruby from magneto-optical measurements under high pressure

Magneto-optical measurements on ruby under high-pressure conditions provided direct determination of the trigonal crystal field acting at the t2g orbitals of Cr3+ in Al2O3 CrO6 and its dependence with pressure. The correlation study between the measured trigonal splitting and the trigonal distortion at the Al3+-substituted site indicates that the trigonal splitting increases with pressure whereas the trigonal distortion slightly reduces. The result is interpreted in terms of an enhancement of the electron-lattice coupling due to trigonal distortion upon reduction in the Al-O bond distance, i.e., the Cr-O bond distance R. The observed variations can be explained on the basis of empirical R dependence of the trigonal crystal field as VtrR?n with n=6. It is shown that this exponent does not change when we consider the pressure variation of the local structure around Cr3+ obtained from ab initio calculations. By the way, we also demonstrate that a methanol-ethanol mixture is a good pressure transmitting medium at cryogenic temperaturesFinancial support from the Spanish Ministerio de Ciencia e Innovación Project No. MAT2008-06873-C02-01, MALTA INGENIO-CONSOLIDER 2010 Grant No. CDS2007-0045, and EuroMagnet II FP7 program are acknowledged

Electronic structure of indium selenide probed by magnetoabsorption spectroscopy under high pressure

We report on an investigation of the peculiar electronic structure of the layered semiconductor InSe by magneto-optical experiments under high pressure up to 5 GPa. Magneto-absorption spectroscopy is performed under pulsed magnetic field up to 53 T using a specific setup. Excitonic magnetofingerprints and high-field oscillatory magnetoabsorption yield significant details on the band structure. In addition, the application of an external pressure unveils phenomena that confirm the specific k·p model proposed for this compound on the basis of earlier measurements

Anharmonic effects in ZnO optical phonons probed by Raman spectroscopy

We report Raman spectroscopy measurements on ZnO crystals grown by the vapor transport method and annealed. Vacuum annealing is found to yield single crystals with ultra low density of defects. We focus on the optical E2 phonon linewidth temperature dependence in the 10?500 K range. The linewidth decrease at low temperature is analyzed and discussed in the light of anharmonic up- and down-conversion processes, unveiling strongly different behaviors for the two E2 phonons

Photoluminescence under high pressure and high magnetic field

International audienc

Physics under pulsed magnetic field up to 60 T

International audienc

Photoluminescence under high pressure and high magnetic field

International audienc