ALBERT

Description: Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69–75), clinopyroxene (Mg# = 75–84), intercumulus plagioclase (An53–86) and Fe–Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than plagioclase and Fe–Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35–39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive Nd i values (4·3–4·8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr–Nd isotopic disequilibrium between clinopyroxene and plagioclase separates: 87 Sr/ 86 Sr i (0·7038–0·7041) and Nd i (1·0–1·9) of clinopyroxene are lower and higher than the respective ratios of intercumulus plagioclase ( 87 Sr/ 86 Sr i = 0·7042–0·7043, Nd i = 0·4–1·0). The 87 Sr/ 86 Sr i and Nd i of clinopyroxene separates correlate positively and negatively with Zr/Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. 87 Sr/ 86 Sr i increases and Nd i decreases with increasing Ca content of plagioclase, indicating that higher An plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and Nd i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean–Neoproterozoic basement and carbonates as contaminants.

Description: Author(s): Fan Zhang, C. L. Kane, and E. J. Mele We introduce a topological boundary condition to study the surface states of topological insulators within a long-wavelength four-band model. We find that the Dirac point energy, the band curvature, and the spin texture of surface states are crystal-face dependent. For an arbitrary termination of a ... [Phys. Rev. B 86, 081303] Published Fri Aug 10, 2012

Description: Author(s): L. Ren, Q. Zhang, C. L. Pint, A. K. Wójcik, M. Bunney, Jr., T. Arikawa, I. Kawayama, M. Tonouchi, R. H. Hauge, A. A. Belyanin, and J. Kono We study macroscopically aligned single-wall carbon nanotube arrays with uniform lengths via polarization-dependent terahertz and infrared transmission spectroscopy. Polarization anisotropy is extreme at frequencies less than ∼100 cm −1 with no sign of attenuation when the polarization is perpendicul... [Phys. Rev. B 87, 161401] Published Tue Apr 02, 2013

Description: Author(s): Fan Zhang, C. L. Kane, and E. J. Mele We study the interaction between a ferromagnetically ordered medium and the surface states of a topological insulator with a general surface termination that were identified recently [F. Zhang et al. Phys. Rev. B 86 081303(R) (2012)]. This interaction is strongly crystal face dependent and can gen... [Phys. Rev. Lett. 110, 046404] Published Fri Jan 25, 2013

Description: Author(s): Fan Zhang, C. L. Kane, and E. J. Mele We propose a feasible route to engineer one- and two-dimensional time-reversal-invariant topological superconductors (SCs) via proximity effects between nodeless s ± wave iron-based SCs and semiconductors with large Rashba spin-orbit interactions. At the boundary of a time-reversal-invariant topologi... [Phys. Rev. Lett. 111, 056402] Published Fri Aug 02, 2013

Description: Author(s): Fan Zhang, C. L. Kane, and E. J. Mele We demonstrate the existence of topological superconductors (SCs) protected by mirror and time-reversal symmetries. D -dimensional ( D =1, 2, 3) crystalline SCs are characterized by 2 D -1 independent integer topological invariants, which take the form of mirror Berry phases. These invariants determine t... [Phys. Rev. Lett. 111, 056403] Published Fri Aug 02, 2013