We report a successful observation of pressure-induced superconductivity in a topological compound Bi 2 Te 3 with T c of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the holetype carrier in the pressure-induced superconducting Bi 2 Te 3 single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi 2 Te 3 due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor.high-pressure effects | pressure-tuned conductivity | topological superconductors U tilizing high pressure can be a very powerful method to generate new materials states, as demonstrated by either highpressure synthesis of new compounds, or pressure-tuned unique electronic states, such as insulator metal transitions. High pressure is particularly effective in tuning superconductivity as it is well documented that the record high superconducting transition temperature T c for either elements (1) or compounds (2) is created with the application of pressure. Recently, topological insulators (TIs) have generated great interest in the area of condensed matter physics (3-8). These materials have an insulating gap in the bulk, while also possessing conducting gapless edges or surface states in the boundaries that are protected by the timereversal symmetry (8, 9). Similar to TIs, topological superconductors have a full pairing gap in the bulk and gapless Majorana states on the edge or surface (10-13, 18). Majorana Fermions (14), half of ordinary Dirac fermions, could be very useful in topological quantum computing (15-17), which is proscriptive for new concept information technology.

Resistance measurements of a "111" type superconductor Li x FeAs ͑x = 0.8, 1.0, 1.1͒ were performed at high pressure. The superconductivity transition temperature ͑T c ͒ is found to decrease almost linearly with increasing pressure and the pressure derivative, dT c / dP, becomes smaller with increasing Li content. Electron spin resonance experiment at ambient pressure on a stoichometric sample shows gradual decrease in the spin moment and the loss of coherence of spin coupling as the temperature is lowered. A very weak Fe local moment is observed when the temperature is lowered to T c. In situ synchrotron radiation powder x-ray diffraction at high pressure shows changes in the resistivity are not related to a structural transition.

The high-pressure behavior of amorphous selenium has been investigated with time-resolved diamond anvil cell synchrotron x-ray diffraction and computed microtomography techniques. A two-step dynamic crystallization process is observed in which the monoclinic phase crystallized from the amorphous selenium and gradually converted to the trigonal phase, thereby explaining previously observed anomalous changes in electrical conductivity of the material under pressure. The crystallization of this elemental system involves local topological fluctuations and results in an unusual pressure-induced volume expansion. The metastability of the phases involved in the transition accounts for this phenomenon. The results demonstrate the use of pressure to control and directly monitor the relative densities and energetics of phases to create new phases from highly metastable states. The microtomographic technique developed here represents a method for determination of the equations of state of amorphous materials at extreme pressures and temperatures.crystallization ͉ volume expansion ͉ equation of state ͉ phase transition ͉ metastability T he behavior of amorphous materials under pressure is a problem of great current interest. Unusual behavior, such as pressure-induced amorphization of crystalline forms, pressureinduced polyamorphism low-to high-density forms of insulating and metallic glasses, and the dynamics of pressure-induced crystallization are reported but not fully understood (1-10). The nature of the behavior of amorphous solids under pressure is complicated by their metastability and the possibility of irreversible relaxation of their properties and structure (11). Amorphous selenium (a-Se) is a model system for examining pressure effects in amorphous materials because of the wide range of structure and bonding properties expected based on the behavior of the crystalline polymorphs of the element. In experiments designed to understand the high-pressure behavior of a-Se, we have discovered an unexpected pressure-induced dynamic crystallization process associated with a volume expansion in the material. The origin of this unusual phenomenon is examined by using a microtomography technique that allows direct measurement of the equation of state (EOS) of the amorphous phase.Recent efforts to characterize the structural evolution of group VI elements under pressure, such as novel dense chain structures in sulfur and selenium (12), and the alternating phase transition sequence in sulfur at high pressure and temperature (13), have led to a new level of understanding of the phase diagrams and structures of these materials. Under pressure, selenium exhibits a complex polymorphism, and the diversity of phases and transition sequences observed depend strongly on the starting material (12,(14)(15)(16)(17)(18)(19)(20)(21). First studied by x-ray diffraction (XRD) in 1972 (22), a-Se was found to crystallize in a trigonal structure (t-Se) at Ϸ10 GPa (23-27). However, its electrical resistance was clearly different from pure t-Se i...

The immobilization of Pseudomonas delafieldii R-8 in calcium alginate beads has been studied in order to improve biodesulfurization activity in oil/water (O/W) biphasic systems. A gas jet extrusion technique was performed to produce immobilized beads. The specific desulfurization rate of 1.5 mm diameter beads was 1.4-fold higher than that of 4.0 mm. Some nonionic surfactants can significantly increase the activity of immobilized cells. The desulfurization rate with the addition of 0.5% Span 80 increased 1.8-fold compared with that of the untreated beads. The rate of biodesulfurization was markedly enhanced by decreasing the size of alginate beads and adding the surfactant Span 80, most likely resulting from the increasing mass transfer of substrate to gel matrix.

The study of nanoscale materials with well-controlled shape could help us to learn more about the morphology effect on phase stability and elastic properties. In situ high-pressure synchrotron angle-dispersive X-ray diffraction for nanobelt and bulk ZnO was measured side-by-side in the same diamond anvil cell at room temperature up to 29 GPa. The pressure-induced wurtzite-type to rocksalt-type structural transition was observed starting at 9.3 GPa for both of these two types of ZnO samples, and no enhanced structural stability for ZnO nanobelts under pressure was found. The relative bigger bulk moduli of wurtzite-and rocksalt-type ZnO nanobelts implicated the morphology effect on its compressibility.