Character of eigenstates of the 3D disordered Anderson Hamiltonian

We study numerically the character of electron eigenstates of the three dimensional disordered Anderson model. Analysis of the statistics of inverse participation ratio as well as numerical evaluation of the electron-hole correlation function confirm that there are no localized states below the mobility edge, as well as no metallic state in the tail of the conductive band. We discuss also finite size effects observed in the analysis of all the discussed quantities.Comment: 7 pages, 9 figures, resubmitted to Physical Review

Transport in the 3-dimensional Anderson model: an analysis of the dynamics on scales below the localization length

Single-particle transport in disordered potentials is investigated on scales below the localization length. The dynamics on those scales is concretely analyzed for the 3-dimensional Anderson model with Gaussian on-site disorder. This analysis particularly includes the dependence of characteristic transport quantities on the amount of disorder and the energy interval, e.g., the mean free path which separates ballistic and diffusive transport regimes. For these regimes mean velocities, respectively diffusion constants are quantitatively given. By the use of the Boltzmann equation in the limit of weak disorder we reveal the known energy-dependencies of transport quantities. By an application of the time-convolutionless (TCL) projection operator technique in the limit of strong disorder we find evidence for much less pronounced energy dependencies. All our results are partially confirmed by the numerically exact solution of the time-dependent Schroedinger equation or by approximative numerical integrators. A comparison with other findings in the literature is additionally provided.Comment: 23 pages, 10 figure

The Role of Power-Law Correlated Disorder in the Anderson Metal-Insulator Transition

We study the influence of scale-free correlated disorder on the metal-insulator transition in the Anderson model of localization. We use standard transfer matrix calculations and perform finite-size scaling of the largest inverse Lyapunov exponent to obtain the localization length for respective 3D tight-binding systems. The density of states is obtained from the full spectrum of eigenenergies of the Anderson Hamiltonian. We discuss the phase diagram of the metal-insulator transition and the influence of the correlated disorder on the critical exponents.Comment: 6 pages, 3 figure

Promoting Atoms into Delocalized Long-Living Magnetically Modified State Using Atomic Force Microscopy

We report on a low-temperature atomic force microscropy manipulation of Co atoms in ultrahigh vacuum on an oxidized copper surface in which the manipulated atom is kept delocalized above several surface unit cells over macroscopic times. The manipulation employed, in addition to the ubiquitous short-range tip-generated chemical forces, also long-range forces generated via Friedel oscillations of the metal charge density due to Co nanostructures prearranged on the surface by lateral manipulation. We show that our manipulation protocol requires mechanical control of the spin state of the Co atom

Critical Importance of van der Waals Stabilization in Strongly Chemically Bonded Surfaces: Cu(110):O

We provide strong evidence that different reconstructed phases of the oxidized Cu(110) surface are stabilized by the van der Waals (vdW) interactions. These covalently bonded reconstructed surfaces feature templates that are an integral part of the surfaces and are bonded on the bare metal surface by a combination of chemical and physical bonding. The vdW stabilization in this class of systems affects predominantly the intertemplate Cu–O interactions in structures sparsely populated by these templates. The conventional dispersionless density functional theory (DFT) methods fail to model such systems. We find a failure to describe the thermodynamics of the different phases that are formed at different oxygen exposures and spurious minima on the potential energy surface of a diffusing surface adatom. To overcome these issues, we employ a range of different DFT methods that account for the missing vdW correlations. Surprisingly, despite vast conceptual differences in the different formulations of these methods, they yield physically identical results for the Cu(110):O surface phases, provided the massive screening effects in the metal are taken into account. Contrary, the vibrational contribution does not consistently stabilize the experimentally observed surface structures. The van der Waals surface stabilization, so far deemed to play only a minor role in hard-bonded surfaces, is suggested to be a more general key feature for this and other related surfaces