Quantum impurity problems occur in various areas of physics. Some examples are: an impurity spin in a metal (the Kondo problem), the two-impurity Kondo problem, a defect or impurity spin in a spin chain, tunnelling through a barrier in a quantum wire proton-monopole scattering (the Callan-Rubakov effect). Some common features of these problems are: 1. gapless “bulk” excitations (ie. far from th...

We introduce a method to obtain the specific heat of quantum impurity models via a direct calculation of the impurity internal energy requiring only the evaluation of local quantitieswithin a single numerical renormalization group (NRG) calculation for the total system. For the Anderson impurity model we show that the impurity internal energy can be expressed as a sum of purely local static cor...

The complete one-phonon density-of-states of a molecular crystal can be mapped out by a carefully chosen exciton sideband involving a localized molecular internal excitation in a dilute isotopic mixed crystal. A theoretical derivation shows that the necessary criteria are: absence of localized in-band phonons; applicability of a phonon amalgamation limit for the mixed crystal; weak exciton-phon...

Abstract We report on impurity diffusion in ion implanted AlN layers after thermal annealing. Silicon, tin, germanium, and magnesium ions were into single-crystal Al-polar grown sapphire substrates. By annealing at 1600 °C, silicon atoms diffused the layer, while less change was observed distribution of germanium atoms. Silicon implantation introduced vacancy-related defects. temperatures over ...

During the synthesis of the bulk drug Raloxifene hydrochloride, eight impurities were observed, four of which were found to be new. All of the impurities were detected using the gradient high performance liquid chromatographic (HPLC) method, whose area percentages ranged from 0.05 to 0.1%. LCMS was performed to identify the mass number of these impurities, and a systematic study was carried out...

Recently we reported on a new isotope effect [1]: During the growth of natural amethyst, Si02 with different lsO content is incorporated at crystallo­ graphically different faces of the crystal, the 180 / 160 ratio increasing in the order z-face, r-face, m-face. Meanwhile a similar effect in natural calcite was re­ ported by J. A. D. Dickson [2]. Care must be taken if one wants to single out su...

We study an Anderson impurity in a semiconducting host using the density matrix renormalization group technique. We use the U = 0 one–dimensional Anderson Hamiltonian at half filling as the semiconducting host since it has a hybridization gap. By varying the hybridization of the host, we can control the size of the semiconducting gap. We consider chains with 25 sites and we place the Anderson i...

This paper presents an analysis of the motion of an neutral impurity species in a nanometer scale 4He cluster, extending a previous study of the dynamics of an ionic impurity. It is shown that for realistic neutral impurity–He potentials, such as those of SF6 and OCS, the impurity is kept well away of the the surface of the cluster by long range induction and dispersion interactions with He, bu...