Giant Negative Magnetoresistance and Strong Electron-Lattice Coupling in Amorphous Semiconductors with Magnetic Impurities

2001 ◽  
pp. 133-140
Author(s):  
A. M. Bratkovsky
Keyword(s):  
Amorphous Semiconductors ◽  
Negative Magnetoresistance ◽  
Magnetic Impurities ◽  
Strong Electron ◽  
Lattice Coupling

ANOMALOUS ELASTIC BEHAVIOR AND ITS CORRELATION WITH SUPERCONDUCTIVITY IN IRON-BASED SUPERCONDUCTOR Ba(Fe1-xCox)2As2

2012 ◽  
Vol 26 (19) ◽  
pp. 1230011 ◽  
Author(s):  
MASAHITO YOSHIZAWA ◽  
SHALAMUJIANG SIMAYI
Keyword(s):  
Elastic Behavior ◽  
Clear Correlation ◽  
Superconducting Transition ◽  
Strong Electron ◽  
Iron Based Superconductors ◽  
Unconventional Superconductors ◽  
Structural Fluctuation ◽  
Iron Based ◽  
Lattice Coupling ◽  
Quantum Critical Behavior

Elastic properties of iron-based superconductor Ba ( Fe 1-x Co x)2 As 2 with various Co concentrations x were reviewed. Among all elastic constants, C66 shows remarkable softening associated with the structural transition from tetragonal to orthorhombic. The amount of anomaly in C66 is 90% for the underdoped samples of x < 0.07 For the overdoped samples, the anomalies in C66 gradually disappear with the increasing of Co concentration. The elastic compliance S66 (= 1/C66) shows a quantum critical behavior, which behaves just like the magnetic susceptibility of unconventional superconductors. There exists a clear correlation between the superconducting transition temperature and the amount of anomaly in S66. It was suggested that the structural fluctuation, which is measured by S66, plays an important role in the emergence of superconductivity. The elastic anomaly of Ba ( Fe 1-x Co x)2 As 2 is characterized by a strong electron–lattice coupling, which would be originated from the 3d orbitals of iron. This might be a universal phenomenon not only in iron-based superconductors but also d-electron based superconductors. The results on Ba ( Fe 1-x Co x)2 As 2 would reveal relevant roles of the structural fluctuations due to the orbitals, which should be taken into account for the understanding of a whole picture of the superconductivity in iron-based superconductors and related materials.

scholarly journals Electron Transport in Carbon Nanotubes with Adsorbed Chromium Impurities

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 524 ◽  
Author(s):  
Stanislav Repetsky ◽  
Iryna Vyshyvana ◽  
Yasuhiro Nakazawa ◽  
Sergei Kruchinin ◽  
Stefano Bellucci
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Cluster Size ◽  
Density Functional ◽  
Tight Binding ◽  
Electrical Current ◽  
Magnetic Impurities ◽  
Binding Model ◽  
Strong Electron ◽  
Electron Phonon Coupling

We employ Green’s function method for describing multiband models with magnetic impurities and apply the formalism to the problem of chromium impurities adsorbed onto a carbon nanotube. Density functional theory is used to determine the bandstructure, which is then fit to a tight-binding model to allow for the subsequent Green’s function description. Electron–electron interactions, electron–phonon coupling, and disorder scattering are all taken into account (perturbatively) with a theory that involves a cluster extension of the coherent potential approximation. We show how increasing the cluster size produces more accurate results and how the final calculations converge as a function of the cluster size. We examine the spin-polarized electrical current on the nanotube generated by the magnetic impurities adsorbed onto the nanotube surface. The spin polarization increases with both increasing concentration of chromium impurities and with increasing magnetic field. Its origin arises from the strong electron correlations generated by the Cr impurities.

Large elastic anomalies and strong electron-lattice coupling in iron-based superconductor Ba(Fe1−xCox)2As2

2012 ◽  
Vol 152 (8) ◽  
pp. 680-687 ◽  
Author(s):  
Masahito Yoshizawa ◽  
Shalamujiang Simayi ◽  
Kohei Sakano ◽  
Yoshiki Nakanishi ◽  
Kunihiro Kihou ◽  
...  
Keyword(s):  
Strong Electron ◽  
Iron Based ◽  
Lattice Coupling ◽  
Elastic Anomalies
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