scholarly journals Kondo temperature when the Fermi level is near a step in the conduction density of states

2017 ◽  
Vol 95 (4) ◽  
Author(s):  
J. Fernández ◽  
A. A. Aligia ◽  
P. Roura-Bas ◽  
J. A. Andrade
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Kondo Temperature

scholarly journals Investigation of single-domain Au silicide nanowires on Si(110) formed for Au coverages in the monolayer regime

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Stephan Appelfeller
Keyword(s):  
Fermi Level ◽  
Surface Structure ◽  
Density Of States ◽  
The Self ◽  
Single Domain ◽  
Photoemission Spectroscopy ◽  
Annealing Temperatures ◽  
Self Organized ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy

AbstractThe self-organized formation of single domain Au silicide nanowires is observed on Si(110). These nanowires are analysed using scanning tunnelling microscopy (STM) and spectroscopy (STS) as well as photoemission spectroscopy (PES). Core-level PES is utilised to confirm the formation of Au silicide and establish its presence as the top most surface structure, i.e., the nanowires. The growth of the Au silicide nanowires and their dimensions are studied by STM. They form for Au coverages of about 1 monolayer and are characterized by widths of about 2 to 3 nm and heights below 1 nm while reaching lengths exceeding 500 nm when choosing appropriate annealing temperatures. Valence band PES and STS indicate a small but finite density of states at the Fermi level typical for compound metals.

Photosensitive tunneling in superconductivity

1970 ◽  
Vol 48 (5) ◽  
pp. 630-631 ◽  
Author(s):  
V. Radhakrishnan
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Tunneling Current ◽  
Theoretical Treatment ◽  
Photoconductive Property

Theoretical treatment of the model proposed by Giaever for his experiment on the photosensitive tunneling in superconductors is examined. New relations are derived which connect the photoconductive property of the barrier and the tunneling current. These relations are helpful to check the model and to determine the density of states for the trapped holes at the hole Fermi level.

scholarly journals An ab-initio study on structural, elastic, electronic, bonding, thermal, and optical properties of topological Weyl semimetal TaX (X = P, As)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. I. Naher ◽  
S. H. Naqib
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Fermi Level ◽  
Density Of States ◽  
Electronic Band Structure ◽  
Optical Parameters ◽  
Electronic Density ◽  
Electronic Band ◽  
Wide Range ◽  
Weyl Semimetals

AbstractIn recent days, study of topological Weyl semimetals have become an active branch of physics and materials science because they led to realization of the Weyl fermions and exhibited protected Fermi arc surface states. Therefore, topological Weyl semimetals TaX (X = P, As) are important electronic systems to investigate both from the point of view of fundamental physics and potential applications. In this work, we have studied the structural, elastic, mechanical, electronic, bonding, acoustic, thermal and optical properties of TaX (X = P, As) in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that both TaP and TaAs possesses low to medium level of elastic anisotropy (depending on the measure), reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature and melting temperature. The minimum thermal conductivities and anisotropies of TaX (X = P, As) are calculated. Bond population analysis supports the bonding nature as predicted by the elastic parameters. The bulk electronic band structure calculations reveal clear semi-metallic features with quasi-linear energy dispersions in certain sections of the Brillouin zone near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding states indicates significant electronic stability of tetragonal TaX (X = P, As).The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes TaX suitable as reflecting coating. TaX (X = P, As) are very efficient absorber of ultraviolet radiation. Both the compounds are moderately optically anisotropic owing to the anisotropic nature of the electronic band structure. The refractive indices are very high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations.

Superconductive Properties of CsxRbyC60 (33K) - Isotope Effect -

1992 ◽  
Vol 247 ◽  
Author(s):  
T. W. Ebbesen ◽  
K. Tanigaki ◽  
S. Saito ◽  
J. Mizuki ◽  
J. S. Tsai ◽  
...  
Keyword(s):  
Fermi Level ◽  
Penetration Depth ◽  
Isotope Effect ◽  
Lattice Constant ◽  
Density Of States ◽  
Coherence Length ◽  
The Other ◽  
First Report ◽  
Electron Coupling

ABSTRACTThe surprisingly high Tc for the superconductivity of alkali doped C60 has spurred wide interest in understanding its mechanism [1–7]. We first report the superconductive properties of CsxRbyC60 which has a Tc as high as 33 K when x=2 and y=1 in the feed [4, 5]. SQUID measurements show that in this material the coherence length is 45 A and the penetration depth about 1, 800 A [5]. It has now been proven that the observed increase in the Tc with the size of the alkali dopant is due to the increase in the lattice constant [6]. This is most likely due to the changes in the density of states at the Fermi level. The other important parameter according to BSC theory is the phonon which mediates the electron-electron coupling. In the second part of this paper we present recent results which show that the Tc is indeed strongly influenced by this parameter [7]. The isotope effect is unexpectedly strong on the Tc.

scholarly journals Strong correlation between electronic bonding network and critical temperature in hydrogen-based superconductors

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Francesco Belli ◽  
Trinidad Novoa ◽  
J. Contreras-García ◽  
Ion Errea
Keyword(s):  
Critical Temperature ◽  
Physical Properties ◽  
Fermi Level ◽  
Electronic Properties ◽  
Density Of States ◽  
Strong Correlation ◽  
Critical Temperatures ◽  
Structural And Electronic Properties ◽  
Superconducting Compounds ◽  
Better Than

AbstractBy analyzing structural and electronic properties of more than a hundred predicted hydrogen-based superconductors, we determine that the capacity of creating an electronic bonding network between localized units is key to enhance the critical temperature in hydrogen-based superconductors. We define a magnitude named as the networking value, which correlates with the predicted critical temperature better than any other descriptor analyzed thus far. By classifying the studied compounds according to their bonding nature, we observe that such correlation is bonding-type independent, showing a broad scope and generality. Furthermore, combining the networking value with the hydrogen fraction in the system and the hydrogen contribution to the density of states at the Fermi level, we can predict the critical temperature of hydrogen-based compounds with an accuracy of about 60 K. Such correlation is useful to screen new superconducting compounds and offers a deeper understating of the chemical and physical properties of hydrogen-based superconductors, while setting clear paths for chemically engineering their critical temperatures.

About the Metal-Insulator Transition in Quasicrystals

2000 ◽  
Vol 643 ◽  
Author(s):  
J. Delahaye ◽  
C. Berger ◽  
T. Grenet ◽  
G. Fourcaudot
Keyword(s):  
Magnetic Field ◽  
Fermi Level ◽  
Electronic Properties ◽  
Field Dependence ◽  
Density Of States ◽  
Disordered Systems ◽  
Magnetic Field Dependence ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Mi Transition

AbstractElectronic properties (conductivity and density of states) of quasicrystals present strong similarities with disordered semiconductor based systems on both sides of the Mott-Anderson metal-insulator (MI) transition. We revisit the conductivity of the i-AlCuFe and i-AlPdMn phases, which has temperature and magnetic field dependence characteristic of the metallic side of the transition. The i-AlPdRe ribbon samples can be on either side of the transition depending on their conductivity value. In all these i-phases, the density of states at the Fermi level EF is low. Its energy dependence close to EF is similar to disordered systems close to the MI transition where it is ascribed to effects of interactions between electrons and disorder.

The Density of States for Chemisorptions on Si (111) Surface

2014 ◽  
Vol 1061-1062 ◽  
pp. 315-318 ◽  
Author(s):  
Jun Fang Wu
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Energy Curve

The density of states was given for the chemisorptions of atom on the Si (111) surface. From these curves, the characteristics, such as the pseudogap, forbidden bandwidth, energy curve, the trend of Fermi level in the graphics and the density of states at the Fermi level and so on, were analyzed and compared to for different elements absorption on the Si (111) surface. The density of states for chemisorptions is different for the different elements.

Accurate Reconstruction of the Density of States in a-Si:H by Photothermal and Photoconductive Spectra.

1993 ◽  
Vol 297 ◽  
Author(s):  
G. Amato ◽  
F. Giorgis ◽  
C. Manfredotti
Keyword(s):  
Iterative Method ◽  
Absorption Coefficient ◽  
Fermi Level ◽  
Density Of States ◽  
Localized States ◽  
Electronic Transitions ◽  
Photothermal Deflection Spectroscopy ◽  
Derivative Method ◽  
Photothermal Deflection ◽  
Made In

The distribution of occupied states in a-Si:H has been inferred by applying a new self- consisting iterative method to the absorption coefficient spectra. This procedure does not require any assumption about the localized states below the Fermi level, and provides a more accurate insight with respect to the simple derivative method. Numerical simulations have been made in order to probe the reliability of our method. The optical spectra have been obtained by means of Photothermal Deflection Spectroscopy (PDS) and Constant Photocurrent Method (CPM); the comparison between the results as obtained by the two techniques suggests that different sensitivities to electronic transitions are involved; this can be used to infer information about the unoccupied defects.

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