Search results for "Tunne"
showing 10 items of 739 documents
Electronic and mechanical characterization of self-assembled alkanethiol monolayers by scanning tunneling microscopy combined with interaction-force-…
1993
We have used scanning tunneling microscopy to study self-assembled monolayers of mercaptohexadecanol in ultrigh vacuum. In addition to tunneling, the interaction force gradient acting between tip and sample was measured. Analysis of the force-gradient data shows that the tip is in mechanical contact with the surface of the monolayer which, in turn, is elastically compressed. The lateral dimensions of the mechanical contact are substantially (approximately five times) larger than the width of the tunneling-current filament. The results suggest that the compression of the monolayer constitutes an integral part of tunneling through the molecules
Experimental demonstration of single-site addressability in a two-dimensional optical lattice
2009
We demonstrate single site addressability in a two-dimensional optical lattice with 600 nm lattice spacing. After loading a Bose-Einstein condensate in the lattice potential we use a focused electron beam to remove atoms from selected sites. The patterned structure is subsequently imaged by means of scanning electron microscopy. This technique allows us to create arbitrary patterns of mesoscopic atomic ensembles. We find that the patterns are remarkably stable against tunneling diffusion. Such micro-engineered quantum gases are a versatile resource for applications in quantum simulation, quantum optics and quantum information processing with neutral atoms.
Violation of the Time-Reversal and Particle-Hole Symmetries in Strongly Correlated Fermi Systems: A Review
2020
In this review, we consider the time reversal T and particle-antiparticle C symmetries that, being most fundamental, can be violated at microscopic level by a weak interaction. The notable example here is from condensed matter, where strongly correlated Fermi systems like heavy-fermion metals and high Tc superconductors exhibit C and T symmetries violation due to so-called non-Fermi liquid (NFL) behavior. In these systems, tunneling differential conductivity (or resistivity) is a very sensitive tool to experimentally test the above symmetry break. When a strongly correlated Fermi system turns out to be near the topological fermion condensation quantum phase transition (FCQPT), it exhibits t…
Phase diagram of a model adsorbate with internal quantum states
1992
Abstract An adsorbate in the strong binding and small corrugation limit is studied. The resulting two-dimensional fluid is treated in the adiabatic approximation: the translations of the heavy molecules are treated classically, whereas the molecular quantum degrees of freedom are modelled by interacting two state tunneling systems. The complete temperature/coverage phase diagram is obtained to a high degree of precision by a new combination of finite size scaling ideas with Path Integral Monte Carlo techniques. Even this simplified adsorbate model possesses a surprisingly complex phase diagram including first- and second-order transitions as well as tricritical and triple points. We identif…
Tuning the Kondo resonance in two-dimensional lattices of cerium molecular complexes
2018
International audience; Cerium intermetallics have raised a lot of interest for the past forty years thanks to their very unusual and interesting electronic and magnetic properties. This can be explained by the peculiar electronic configuration of Ce (4f1) that allows different oxidation states leading to singular behavior such as quantum phase transitions, heavy-fermion behavior and the Kondo effect. In this work, we used a mixed-valence molecular analogue to study the Kondo effect down to the atomic scale by means of scanning tunneling microscopy/spectroscopy (STM/STS) for which new many-body effects are expected to emerge due to reduced dimensionality and specific chemical environment of…
Intermolecular potential and rovibrational states of the H2O–D2 complex
2012
International audience; A five-dimensional intermolecular potential for H2O-D-2 was obtained from the full nine-dimensional ab initio potential surface of Valiron et al. [P. Valiron, M. Wernli, A. Faure, L. Wiesenfeld, C. Rist, S. Kedzuch, J. Noga, J. Chem. Phys. 129 (2008) 134306] by averaging over the ground state vibrational wave functions of H2O and D-2. On this five-dimensional potential with a well depth D-e of 232.12 cm (1) we calculated the bound rovibrational levels of H2O-D-2 for total angular momentum J = 0-3. The method used to compute the rovibrational levels is similar to a scattering approach-it involves a basis of coupled free rotor wave functions for the hindered internal r…
Self-trapped holes and recombination luminescence in LiBaF3 crystals
2001
Abstract We investigated electron paramagnetic resonance (EPR) angular dependencies, recombination afterglow and thermostimulated luminescence of undoped LiBaF3 crystals, X-irradiated at low temperatures. EPR parameters of the F2− molecule oriented along the [1 1 0] direction have been obtained. Based on the value of the g-shift Δg=g⊥−gII=0.02, characteristic for the VK-centres in similar perovskites, we propose that we indeed observed the VK-centres, not the H-centres. X-irradiation below 170 K results in creation of a long-time temperature-independent afterglow due to the tunnelling recombination between close electron and hole centres. The F-type electron centres and the VK as well as pr…
Spectral Measurement of Photon Emission from Individual Gold Nanoparticles Using Scanning Tunneling Microscopy
2016
The light emission spectra of individual Au nanoparticles induced by a scanning tunneling microscope (STM) have been investigated. Two-dimensional ensembles of tunnel-coupled Au particles were prepared by thermal evaporation onto a native oxide silicon wafer in ultrahigh vacuum (10 – 9 mbar). Our STM measurements show a single peak at photon energy 1.6 eV in the tunneling mode and two peaks at 2.2 eV (connected with the Mie plasmon) and 1.45 eV (a new peak which was not discussed in literature before) in the field emission mode.
Localised transitions in luminescence of AlN ceramics
2014
Abstract The photoluminescence (PL) and thermoluminescence (TL) properties of AlN ceramics revealed under UV irradiation are determined mainly by oxygen-related centres, giving rise to the UV (around 3.18 eV) and the Blue (2.58 eV) bands. It was found that the UV irradiation-generated donor–acceptor pairs (DAPs), responsible for the UV emission band, are randomly distributed with regard to separation distance. Luminescence properties of AlN are interpreted basing on the model of localised recombination involving electron tunnel transitions from the excited state of D to the ground state of A, proposed by Jain et al. (2012) . The observed features of PL, afterglow and TL of AlN ceramics are …
Trap spectroscopy and tunnelling luminescence in feldspars
1998
Abstract Comparative studies of tunnel luminescence, thermally stimulated luminescence (TSL), and trap energy spectra by the fractional glow technique (FGT) have been made both with sanidine and microcline feldspars. After X-irradiation at LNT these feldspars show intense tunnelling afterglow. As the temperature is raised, several TSL glow peaks may be observed, starting at 135 K. An intense peak at 250 K is common to all four investigated microclines. In samples of sanidine, tunnelling afterglow overcomes TSL up to 250–260 K. With sanidine and microcline samples, the distributions of trap activation energies vs temperature obtained by the FGT are continuous and quasi-linear. Maxima in the …