oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 88 )

2019 ( 400 )

2018 ( 418 )

2017 ( 436 )

Custom range...

Search Results: 1 - 10 of 214318 matches for " I. K. Yanson "
All listed articles are free for downloading (OA Articles)
Page 1 /214318
Display every page Item
Phonon structure in point-contact spectra of MgB$_2$
I. K. Yanson
Physics , 2004,
Abstract: In strong-coupling superconductors with a short electron mean free path the self-energy effects in the superconducting order parameter play a major role in the phonon manifestation of the point-contact spectra at above-gap energies. We compare the expressions for the nonlinear conductivity of tunnel, ballistic, and diffusive point-contacts and show that these expression are similar and correspond to the measurements of the phonon structure in the point-contact spectra for the $\pi$-band of MgB$_{2}$.
Point-Contact Spectroscopy of Superconductors
I. K. Yanson
Physics , 2000,
Abstract: The point-contact spectroscopy, in contrast to the tunneling spectrocopy, considers small electrical contacts with direct conductivity. In the normal state, it enables one to measure the spectral function of electron-boson interaction. In the superconducting state, new features appear connected with the energy dependence of excess current. The non-linearities of the current-voltage characteristic are due to: i) The inelastic scattering of electron quasiparticles in the contact region; ii) The energy dependence of the superconducting energy gap, and iii) The non-equilibrium superconducting effects. These effects are discussed from the experimental point of view
Andreev-reflection and Point-Contact Spectroscopy of Superconducting Rare Earth Transition Metal Borocarbides
I. K. Yanson
Physics , 2000,
Abstract: The superconducting energy gap and quasiparticle density of states (DOS) is measured by means of Andreev-reflection spectroscopy in normal metal - superconductor point contacts. It is found that both in paramagnetic and in antiferromagnetically ordered states (Tm- and Dy-compounds) the DOS has the BCS-like form while in Er- the dip in the temperature dependence of the gap is observed at the Neel temperature. In Ho-compound, the non-BCS-like form of DOS is observed in the temperature region where the incommensurate spin density waves exist along the axes a and c . Inelastic point-contact spectroscopy performed on these compounds shows that the low-frequency phonons are important for the superconducting state which are strongly mixed with the magnetic excitation branches in magnetic superconductors.
Shell-effects in heavy alkali-metal nanowires
A. I. Yanson,I. K. Yanson,J. M. van Ruitenbeek
Physics , 2004,
Abstract: We supplement our previous observations of the shell effect in alkali-metal nanowires (Li, Na, K) with data extended to the heavy alkalis Rb and Cs. Our observations include: i) a non-monotonous dependence of conductance-histogram peak heights on atomic weight, ii) a rapid transition to an atomic shell structure at elevated temperatures, and iii) a ''reverse'' atomic-electronic shell transition, caused by the closeness to the liquid state.
Crossover from Electronic to Atomic Shell Structure in Alkali Metal Nanowires
A. I. Yanson,I. K. Yanson,J. M. van Ruitenbeek
Physics , 2001, DOI: 10.1103/PhysRevLett.87.216805
Abstract: After making a cold weld by pressing two clean metal surfaces together, upon gradually separating the two pieces a metallic nanowire is formed, which progressively thins down to a single atom before contact is lost. In previous experiments [1,2] we have observed that the stability of such nanowires is influenced by electronic shell filling effects, in analogy to shell effects in metal clusters [3]. For sodium and potassium at larger diameters there is a crossover to crystalline wires with shell-closings corresponding to the completion of additional atomic layers. This observation completes the analogy between shell effects observed for clusters and nanowires.
Observation of Supershell Structure in Alkali Metal Nanowires
A. I. Yanson,I. K. Yanson,J. M. van Ruitenbeek
Physics , 2000, DOI: 10.1103/PhysRevLett.84.5832
Abstract: Nanowires are formed by indenting and subsequently retracting two pieces of sodium metal. Their cross-section gradually reduces upon retraction and the diameters can be obtained from the conductance. In previous work we have demonstrated that when one constructs a histogram of diameters from large numbers of indentation-retraction cycles, such histograms show a periodic pattern of stable nanowire diameters due to shell structure in the conductance modes. Here, we report the observation of a modulation of this periodic pattern, in agreement with predictions of a supershell structure.
Observation of shell structure in sodium nanowires
A. I. Yanson,I. K. Yanson,J. M. van Ruitenbeek
Physics , 1999,
Abstract: The quantum states of a system of particles in a finite spatial domain in general consist of a set of discrete energy eigenvalues; these are usually grouped into bunches of degenerate or close-lying levels, called shells. In fermionic systems, this gives rise to a local minimum in the total energy when all the states of a given shell are occupied. In particular, the closed-shell electronic configuration of the noble gases produces their exceptional stability. Shell effects have previously been observed for protons and neutrons in nuclei and for clusters of metal atoms. Here we report the observation of shell effects in an open system - a sodium metal nanowire connecting two bulk sodium metal electrodes, which are progressively pulled apart. We measure oscillations in the statistical distribution of conductance values, for contact cross-sections containing up to a hundred atoms or more. The period follows the law expected from shell-closure effects, similar to the abundance peaks at `magic numbers' of atoms in metal clusters.
Point-contact spectroscopy of two-band superconductor MgB2
I. K. Yanson,Yu. G. Naidyuk
Physics , 2003,
Abstract: The progress in investigation of two-band superconductor MgB$_2$ by the point-contact spectroscopy (PCS) is given. Results of study of superconducting gap temperature and magnetic field dependence for two-dimensional $\sigma$ and three-dimensional $\pi$ band and electron-phonon-interaction spectral function are presented. Correlation between the gap value and the intensity of the high T$_c$ driving force -- $E_{2g}$ boron vibration mode, is provided. PCS data on some nonsuperconducting transition metal diborides are surveyed for comparison.
Advances in point-contact spectroscopy: two-band superconductor MgB2 (A review)
I. K. Yanson,Yu. G. Naidyuk
Physics , 2004, DOI: 10.1063/1.1704612
Abstract: Analysis of the point-contact spectroscopy (PCS) data on the new dramatic high-T$_c$ superconductor MgB$_2$ reveals quite different behavior of two disconnected $\sigma$ and $\pi$ electronic bands, deriving from their anisotropy, different dimensionality, and electron-phonon interaction. PCS allows direct registration of both the superconducting gaps and electron-phonon-interaction spectral function of the two-dimensional $\sigma$ and three-dimensional $\pi$ band, establishing correlation between the gap value and intensity of the high-T$_c$ driving force -- the $E_{2g}$ boron vibration mode. PCS data on some nonsuperconducting transition-metal diborides are surveyed for comparison.
Point-Contact Spectroscopy
Yu. G. Naidyuk,I. K. Yanson
Physics , 2003,
Abstract: The history is described of how one of the most commonly used electric circuit components, an ordinary electric contact, has become a powerful tool for the physicists to study various mechanisms of electron scattering in metals. The physical principles of spectroscopy of quasi-particle excitations in metals by means of point contacts (PCs) whose dimensions range from only a few to tens of nanometers are presented in a popular form.
Page 1 /214318
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.