MOCVD synthesis of compositionally tuned topological insulator nanowires

Device applications involving topological insulators (TIs) will require the development of scalable methods for fabricating TI samples with sub-micron dimensions, high quality surfaces, and controlled compositions. Here we use Bi-, Se-, and Te-bearing metalorganic precursors to synthesize TIs in the form of nanowires. Single crystal nanowires can be grown with compositions ranging from Bi2Se3 to Bi2Te3, including the ternary compound Bi2Te2Se. These high quality nanostructured TI compounds are suitable platforms for on-going searches for Majorana Fermions

R-matrices and Tensor Product Graph Method

A systematic method for constructing trigonometric R-matrices corresponding to the (multiplicity-free) tensor product of any two affinizable representations of a quantum algebra or superalgebra has been developed by the Brisbane group and its collaborators. This method has been referred to as the Tensor Product Graph Method. Here we describe applications of this method to untwisted and twisted quantum affine superalgebras.Comment: LaTex 7 pages. Contribution to the APCTP-Nankai Joint Symposium on "Lattice Statistics and Mathematical Physics", 8-10 October 2001, Tianjin, Chin

In-plane thermal conductivity of large single crystals of Sm-substituted (Y1−x_{1-x}Smx_{x})Ba2_{2}Cu3_{3}O7−δ_{7-\delta}

We have investigated the in-plane thermal conductivity $\kappa_{ab}(T,H)$ of large single crystals of optimally oxygen-doped (Y$_{1-x}$,Sm$_{x}$)Ba$_{2}$Cu$_{3}$O$_{7-\delta}$ ($x$=0, 0.1, 0.2 and 1.0) and YBa$_{2}$(Cu$_{1-y}$Zn$_{y}$)$_{3}$O$_{7-\delta}$($y$=0.0071) as functions of temperature and magnetic field (along the c axis). For comparison, the temperature dependence of $\kappa_{ab}$ for as-grown crystals with the corresponding compositions are presented. The nonlinear field dependence of $\kappa_{ab}$ for all crystals was observed at relatively low fields near a half of $T_{c}$. We make fits of the $\kappa(H)$ data to an electron contribution model, providing both the mean free path of quasiparticles $\ell_{0}$ and the electronic thermal conductivity $\kappa_{e}$, in the absence of field. The local lattice distortion due to the Sm substitution for Y suppresses both the phonon and electron contributions. On the other hand, the light Zn doping into the CuO $_{2}$ planes affects solely the electron component below $T_{c}$, resulting in a substantial decrease in $\ell_{0}$ .Comment: 7 pages,4 figures,1 tabl

Large anomalous Hall effect in ferromagnetic insulator-topological insulator heterostructures

We demonstrate the van der Waals epitaxy of the topological insulator compound Bi2Te3 on the ferromagnetic insulator Cr2Ge2Te6. The layers are oriented with (001) of Bi2Te3 parallel to (001) of Cr2Ge2Te6 and (110) of Bi2Te3 parallel to (100) of Cr2Ge2Te6. Cross-sectional transmission electron microscopy indicates the formation of a sharp interface. At low temperatures, bilayers consisting of Bi2Te3 on Cr2Ge2Te6 exhibit a large anomalous Hall effect (AHE). Tilted field studies of the AHE indicate that the easy axis lies along the c-axis of the heterostructure, consistent with magnetization measurements in bulk Cr2Ge2Te6. The 61 K Curie temperature of Cr2Ge2Te6 and the use of near-stoichiometric materials may lead to the development of spintronic devices based on the AHE.Comment: Related papers at http://pettagroup.princeton.ed

Time-odd triaxial relativistic mean field approach for nuclear magnetic moments

The time-odd triaxial relativistic mean field approach is developed and applied to the investigation of the ground-state properties of light odd-mass nuclei near the double-closed shells. The nuclear magnetic moments including the isoscalar and isovector ones are calculated and good agreement with Schmidt values is obtained. Taking $^{17}$F as an example, the splitting of the single particle levels (around $~0.7$ MeV near the Fermi level), the nuclear current, the core polarizations, and the nuclear magnetic potential, i.e., the spatial part of the vector potential, due to the violation of the time reversal invariance are investigated in detail.Comment: 26 pages, 8 figures. PHYSICAL REVIEW C (accepted

Searching for 4α\alpha linear-chain structure in excited states of 16^{16}O with a covariant density functional theory

A study of 4$\alpha$ linear-chain structure in high-lying collective excitation states of $^{16}$O with a covariant density functional theory is presented. The low-spin states are obtained by configuration mixing of particle-number and angular-momentum projected quadrupole deformed mean-field states with generator coordinate method. The high-spin states are determined by cranking calculations. These two calculations are based on the same energy density functional PC-PK1. We have found a rotational band at low-spin with the dominated intrinsic configuration considered to be the one that 4$\alpha$ clusters stay along a common axis. The strongly deformed rod shape also appears in the high-spin region with the angular momentum $13-18\hbar$; however whether the state is pure $4\alpha$ linear chain or not is less obvious than that in the low-spin states.Comment: 10 pages with 11 figures and 3 table