The Large Helical Device (LHD) and Wendelstein 7-X (W7-X, under construction) are experiments specially designed to demonstrate long pulse (quasi steady-state) operation, which is an intrinsic property of Stellarators and Heliotrons. Significant progress was made in establishment of high performance plasmas. A crucial point is the increasing impurity confinement towards high density as observed...

We discuss the broadening of ground-state to bounded excited-state transitions of shallow donors in strongly compensated n-type Ge : (As,Ga) in the presence of electric fields and their gradients, arising from randomly distributed ionized impurities. Quantitative comparison of the experimentally obtained linewidths with Monte Carlo simulation results makes possible, a unique determination of th...

We study the properties of localized impurity modes and the transmission of plane waves across a general nonlinear impurity embedded in an infinite one-dimensional linear chain. Using the formalism of the lattice Green function, we obtain nonlinear equations for the bound state energy and the transmission coefficient, for a wide class of nonlinear impurities. We specialize to a saturable nonlin...

Optical spectra of a self-organized quantum dot with a single magnetic impurity are studied. The quantum dot potential and exchange interactions result in an additional fine structure of an exciton localized in a quantum dot with a magnetic impurity. In contrast to the undoped quantum dots, the ground state excitons in the quantum dot with a magnetic impurity are bright. It is also shown that a...

We compute the single-particle inverse lifetime, along with the conductivity-derived scattering rate, for a metallic system in an s-wave superconducting state. When both electron-phonon and electron-impurity scattering are included , we find that while these scattering rates are in qualitative agreement, in general quantitative agreement is lacking. We also derive results for the quasiparticle ...

We consider a strongly correlated ladder with diagonal hopping and exchange interactions described by t − J type hamiltonian. We study the dynamics of a single hole in this model in the presence of a static non-magnetic (or magnetic) impurity. In the case of a non-magnetic (NM) impurity we solve the problem analytically both in the triplet (S=1) and singlet (S=0) sectors. In the triplet sector ...

Impurity transport coefficients and the penetration efficiencies of intrinsic and injected impurities through the separatrix of diverted Al-cator C-Mod discharges have been measured using x-ray and VUV spec-troscopic diagnostics. The dominant low Z intrinsic impurity in C-Mod is carbon which is found to be present in concentrations of less than 0.5%. Molybdenum, from the plasma facing component...

We investigate the optical conductivity of a Hubbard ring in presence of an impurity by means of exact diagonalization using the Lanczos algorithm. We concentrate thereby on the first excited, open shell state, i.e. on twisted boundary conditions. In the metallic phase a substantial part of the spectral weight lies in the Drude peak, σ(ω) = Dcδ(ω)+σreg . In the non-interacting system, the Drude...

We perform self-consistent studies of two-dimensional (2D) s-wave topological superconductivity (TSC) with Rashba spin-orbit coupling and Zeeman field by solving the Bogoliubov-de Gennes equations. In particular, we examine the effects of a nonmagnetic impurity in detail and show that the nature of the spin-polarised midgap bound state varies significantly depending on the material parameters. ...