Search results for "Tunnelling"
showing 10 items of 218 documents
Electron–phonon coupling in degenerate silicon-on-insulator film probed using superconducting Schottky junctions
2002
Abstract Energy flow rate in degenerate n-type silicon-on-insulator (SOI) film is studied at low temperatures. The electrons are heated above the lattice temperature by electric field and the electron temperature is measured via semiconductor–superconductor quasiparticle tunneling. The energy flow rate in the system is found to be proportional to T 5 , indicating that electron–phonon relaxation rate and electron–phonon phase breaking rate are proportional to T 3 . The electron–phonon system in the SOI film is in the “dirty limit” where the electron mean free path is smaller than the inverse of the thermal phonon wave vector.
Resonant Tunneling through a Macroscopic Charge State in a Superconducting Single Electron Transistor
1997
We predict theoretically and observe in experiment that the differential conductance of a superconducting single electron transistor exhibits a peak which is a complete analog, in a macroscopic system, of a standard resonant tunneling peak associated with tunneling through a single quantum state. In particular, in a symmetric transistor, the peak height is universal and equal to ${e}^{2}/2\ensuremath{\pi}\ensuremath{\Elzxh}$. Away from the resonance we clearly observe the cotunneling current which, in contrast to the normal-metal transistor, varies linearly with the bias voltage.
Heavy-fermion superconductivity induced by antiferromagnetic spin fluctuations
2007
Superconductivity is caused by an attractive interaction between electrons at the Fermi level that induces the pairing of time-reversed electron states to Cooper pairs. Conventionally this attractive interaction is mediated by phonons. Theoretically, non-phonon mediated coupling seems to be likely for heavy-fermion superconductors whose low-temperature dynamics is dominated by antiferromagnetic spin correlations. However, evidence for spin-fluctuation coupling has not yet been experimentally observed. One of the most direct methods of investigation of the superconducting state is tunneling spectroscopy. We prepared cross-type tunneling junctions composed of the heavy-fermion superconductor …
Josephson junctions and superconducting field effect transistors based on epitaxial Bi2Sr2Can-1CunO2(n+2) thin films
1998
Abstract Josephson junctions based on thin films of the Bi2Sr2Ca2Cu3O10+δ compound show IcRn products compatible with YBa2Cu3O7−δ samples. Using quasiparticle tunneling experiments we found evidence for a superconductor–insulator–superconductor tunneling process via localized states in the barrier. The Bi2Sr2CaCu2O8+δ compound is investigated regarding possible applications in superconducting field effect devices. We present thin films of four unit cells thickness that are superconducting at 58 K. An inverted metal–insulator–superconductor structure was prepared. From the modulation of the normal state resistance we estimate a carrier density of 7×1019 cm−3 for a superconducting sample. The…
Effect of carrier transfer on the PL intensity in self-assembled In (Ga) As/GaAs quantum rings
2006
We present results concerning the carrier transfer between In(Ga)As quantum rings in a stacked multilayer structure, which is characterised by a bimodal size distribution. This transfer of carriers explains the observed temperature behaviour of diode lasers based on that kind of stacked layer structures. The inter-ring carrier transfer can be possible by phonon assisted tunnelling from the ground state of the smallring family towards the big-ring family of the bimodal size distribution. This process is thermally activated in the range 40–80 K.
Ridge-enhanced optical transmission through a continuous metal film
2004
Optical transmission through a continuous (without holes) metal film with a periodic structure of metal or dielectric ridges on one or both interfaces was numerically studied. The dependencies of the transmission on the ridge width and height as well as the ridge arrangements on the opposite interfaces were investigated in weak- and strong-coupling regimes. The transmission enhancement was shown to depend on the relative position of the ridge gratings on the opposite interfaces of a film, confirming the role of resonant tunneling processes involving states of the surface polariton Bloch modes.
Fluorinated Fullerene Molecule on Cu(001) Surface as a Controllable Source of Fluorine Atoms
2018
A coverage-dependent growth of well-ordered copper halogenide structures as a result of fluorinated fullerene molecule adsorption on Cu(001) surface has been studied by means of scanning tunneling ...
Oxide growth and tunneling characteristics of Sn-SnO x -Sn junctions
1979
Sn—SnOx—Sn tunneling junctions were prepared by thermal oxidation of vacuum deposited Sn-films. The thickness growth of the oxide was followed by ellipsometric measurements. From logarithmic conductivity measurements the barrier heights were determined. The tunneling characteristic could be well described by the two-band-tunneling model using a value of 0.14 for the ratio of the effective masses in the oxide and the metal.
Magnetic nanoparticles between electrodes of tunnel junction: anomalous tunnel conductance
2002
Abstract Magnetic particles of microscopic size can be created in the process of Ni, Fe and Co mechanically controllable break junctions fabrication and trapped between the electrodes by magnetic dipole forces. Tunneling between the protruding nanoparticle and the sample electrode shows clear distinctions from the usual junctions: heavy deviation of the current–distance I(z) dependence from the expected exponential behavior at electrode separations z below 4.0– 4.5 A and on numerous occasions a sudden jump-like decrease of the tunnel current at z≈1.5– 2.0 A . Possible mechanisms behind observed anomalies including the short-range magnetic exchange coupling are discussed.
Correction: “On-the-fly” coupled cluster path-integral molecular dynamics: impact of nuclear quantum effects on the protonated water dimer
2015
We present an accelerated ab initio path-integral molecular dynamics technique, where the interatomic forces are calculated “on-the-fly” by accurate coupled cluster electronic structure calculations. In this way not only dynamic electron correlation, but also the harmonic and anharmonic zero-point energy, as well as tunneling effects are explicitly taken into account. This method thus allows for very precise finite temperature quantum molecular dynamics simulations. The predictive power of this novel approach is illustrated on the example of the protonated water dimer, where the impact of nuclear quantum effects on its structure and the 1H magnetic shielding tensor are discussed in detail.