scholarly journals Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser

Science ◽  
2017 ◽  
Vol 357 (6346) ◽  
pp. 71-75 ◽  
Author(s):  
S. Gerber ◽  
S.-L. Yang ◽  
D. Zhu ◽  
H. Soifer ◽  
J. A. Sobota ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Electronic Band Structure ◽  
Phonon Coupling ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Structure Comparison ◽  
X Ray ◽  
Iron Selenide ◽  
Electron Phonon Coupling ◽  
Lock In

The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a “coherent lock-in” measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

scholarly journals Temperature-dependent electron-phonon coupling in La2−xSrxCuO4probed by femtosecond x-ray diffraction

2013 ◽  
Vol 88 (5) ◽  
Author(s):  
B. Mansart ◽  
M. J. G. Cottet ◽  
G. F. Mancini ◽  
T. Jarlborg ◽  
S. B. Dugdale ◽  
...  
Keyword(s):  
Phonon Coupling ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Electron Phonon Coupling

Transmissionsoptimierte Einkristallstrukturbestimmung und elektronische Struktur von Bi3Ni / Transmission-Optimized Single-Crystal Structure Determination and Electronic Structure of Bi3Ni

2006 ◽  
Vol 61 (7) ◽  
pp. 785-791 ◽  
Author(s):  
Michael Ruck ◽  
Tilo Söhnel
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Electronic Band Structure ◽  
Structural Fragment ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Interatomic Distances ◽  
X Ray ◽  
Absorption Correction ◽  
Trigonal Prismatic Coordination

Crystals of Bi3Ni were synthesized using iodine as mineralizer. X-ray diffraction on a single-crystal including transmission-optimized measurement and optimized absorption correction (μ(Mo-Kα) = 1302 cm−1) results in a structure model (Pnma; a = 887.96(7), b = 409.97(3), c = 1147.8(1) pm) with significant deviations in interatomic distances compared with previous data from X-ray and neutron investigations. From quantum chemical calculations and from the structural chemistry of the subhalides related to Bi3Ni the chemical structure of the intermetallic compound can be derived. In the crystal structure the Ni atoms have a capped trigonal prismatic coordination of Bi atoms with strong bonds Ni-Bi and Ni-Ni. The prisms constitute rods 1∞ [NiBi1/1Bi6/3] by sharing the non-capped square faces. The bonding between the intermetallic rods is clearly weaker than inside them, leading to a preservation of this structural fragment in the subhalides of Bi3Ni. In accordance with the low temperature superconductivity of the compound, its electronic band structure shows steep and flat bands at the Fermi level. DFT and ELF calculations reveal a separation of delocalized conduction electrons inside the prism rods and largely localized valence electrons between them.

Single-Crystal X-Ray Diffraction and Electronic Band Structure Studies of PdTeI

1998 ◽  
Vol 137 (2) ◽  
pp. 206-210 ◽  
Author(s):  
D.-K. Seo ◽  
M.-H. Whangbo ◽  
K. Neininger ◽  
G. Thiele
Keyword(s):  
Band Structure ◽  
Single Crystal ◽  
Electronic Band Structure ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
X Ray

scholarly journals On the Superconductivity Suppression in Eu1−xPrxBa2Cu3O7−δ

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3503
Author(s):  
Paweł Pęczkowski ◽  
Piotr Zachariasz ◽  
Cezariusz Jastrzębski ◽  
Jarosław Piętosa ◽  
Elżbieta Drzymała ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Low Temperature ◽  
Magnetic Moment ◽  
Schematic Diagram ◽  
Optical Phonons ◽  
Phonon Coupling ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electron Phonon Coupling ◽  
X Ray Absorption

This article reports on the non-trivial suppression of superconductivity in the Eu1−xPrxBCO cuprates. As non-magnetic Eu3+ ions are replaced by Pr3+ carrying a magnetic moment, spin-related superconductivity loss can be expected. The research shows that the superconductivity disappearance for x > 0.4 results from depletion of the carriers and their localization. The above conclusion was drawn by low-temperature X-ray diffraction analysis showing increased characteristic phonon frequencies with Pr content. This mechanism should promote electron–phonon coupling, at least for acoustic phonons. However, the inverse phenomenon was detected. Namely, there is a gradual deterioration of the optical phonons responsible for vibration of the Cu–O bonds with Pr increasing, as evidenced by Raman spectroscopy. Furthermore, the results of X-ray absorption spectroscopy precisely showed the location of the carriers for Pr-rich specimens. Finally, a schematic diagram for Eu1−xPrxBCO is proposed to consolidate the presented research.

ELECTRONIC STRUCTURE, MAGNETIC ORDERING AND PHASE STABILITY OF LiFeX (X = P, As and Sb) UNDER PRESSURE

2013 ◽  
Vol 27 (32) ◽  
pp. 1350236 ◽  
Author(s):  
RAJENDRAN MAHESH ◽  
RAMASWAMY MURUGAN ◽  
BALAN PALANIVEL
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Magnetic Ordering ◽  
Coupling Constant ◽  
Phonon Coupling ◽  
Electronic Band ◽  
Electron Phonon Coupling ◽  
Total Energies ◽  
Quantum Espresso

Electronic band structure calculations were performed on the nonmagnetc (NM) and antiferromagnetic (AFM) phases of LiFe X (X = P , As and Sb ) compounds using ab initio method. The crystal structure of these compounds is well tetragonal P4/nmm structure (space group = 129). Self-consistent calculations were performed by planewave pseudo-potential, density functional based method using PWSCF-Quantum Espresso code. To study the electronic structure and magnetic ordering, the total energies of these compounds have been computed as a function of reduced volumes and fitted with Brich Murnaghan equation. The estimated lattice parameters are in good agreement with available experimental data. The calculated Fe magnetic moment for LiFeSb is larger than LiFeAs and LiFeP . The obtained electron–phonon coupling constant (λ) for the NM phase are very weak when compared to that of AFM phase of LiFe X compounds. Present calculations reveal that the electron–phonon coupling constant λ decreases as a function of pressure.

scholarly journals Ab-initio studies of thermal and superconducting properties of HfX2 alloys (X = Tc, Re, and Os)

2014 ◽  
Vol 32 (3) ◽  
pp. 324-330 ◽  
Author(s):  
V. Sathyakumari ◽  
S. Sankar ◽  
K. Mahalakshmi
Keyword(s):  
Band Structure ◽  
Electronic Band Structure ◽  
Tight Binding ◽  
Coupling Constant ◽  
Phonon Coupling ◽  
Electronic Band ◽  
Atomic Sphere ◽  
Electron Phonon Coupling ◽  
Sphere Approximation ◽  
Specific Heat Coefficient

AbstractA systematic study of thermal properties such as the Debye temperature, specific heat coefficient, Grüneisen constant, electron-phonon coupling constant and transition temperature have been carried out using the results of electronic band structure and related characteristics, for hafnium superconducting alloys, namely, HfTc2, HfRe2 and HfOs2. Computation of the electronic band structure and associated properties has been carried out using the tight-binding-linear-muffin-tin-orbital (TBLMTO) method within atomic sphere approximation (ASA). The calculated values have been compared with the available results of literature data.

scholarly journals Superconductivity in Diamond-like BC3 Phase

2010 ◽  
Vol 2 (2) ◽  
pp. 203-213 ◽  
Author(s):  
M. M. Ali ◽  
A.K.M. A. Islam ◽  
M. Aftabuzzaman ◽  
F. Parvin
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Density Functional Method ◽  
Metallic Phase ◽  
Tetragonal Symmetry ◽  
Phonon Coupling ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Electron Phonon Coupling

Two possible phases of superhard material BC3 originating from the cubic diamond structure are investigated by ab initio pseudopotential density functional method using generalized gradient approximation (GGA). We calculate their elastic constants, electronic band structure, and density of states (DOS). Full phonon frequencies, electron-phonon coupling constant and possible superconducting Tc of the metallic phase with tetragonal symmetry (t-BC3, space group P-42m) have for the first time been investigated at 5 and 10 GPa. The calculated electron-phonon coupling (0.67) and the logarithmically-averaged frequency (862 cm-1) show superconductivity for the undoped t-BC3 with Tc = 20 K at 5 GPa, which decreases to 17.5 K at 10 GPa. Keywords: Superhard BC3; Band structure; Phonon spectra; Superconductivity. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.DOI: 10.3329/jsr.v2i2.2638               J. Sci. Res. 2 (2), 203-213 (2010)     

Sign in / Sign up

Export Citation Format

Share Document