scholarly journals Pressure-dependent topological superconductivity on the surface of FeTe0.5Se0.5

2022 ◽  
Author(s):  
Chih-Kai Yang ◽  
Chi-Hsuan Lee
Keyword(s):  
Exchange Interaction ◽  
Density Functional ◽  
Applied Pressure ◽  
Bcs Theory ◽  
Superconducting Gap ◽  
Cooper Pairs ◽  
S Wave ◽  
Iron Based Superconductors ◽  
Iron Based ◽  
Critical Temperature Tc

Abstract FeTe1-xSex is a family of iron-based superconductors with its critical temperature (Tc) dependent on the composition of Se. A well-known Tc is 14.5 K for x = 0.45, which exhibits an s-wave superconducting gap between the topological superconducting surfaces states. Exchange interaction between the electrons has been proposed as the mechanism behind the formation of Cooper pairs for the sample of FeTe0.5Se0.5. In this article we provide further proof that exchange interaction, and hence the associated Tc, depends on the applied pressure on FeTe0.5Se0.5. Using density functional calculations for electrons and phonons and the Bardeen-Cooper-Schrieffer (BCS) theory for superconductivity, we found that Tc and superconducting gap for FeTe0.5Se0.5 soars under increasing compression, consistent with the results of experiment.

scholarly journals Strong enhancement of magnetic order from bulk to stretched monolayer FeSe as Hund’s metals

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Chang-Youn Moon
Keyword(s):  
Density Functional ◽  
Magnetic Order ◽  
Mean Field Theory ◽  
Mean Field ◽  
Comprehensive Understanding ◽  
Functional Theory ◽  
Iron Based Superconductors ◽  
Magnetic Orders ◽  
Spatial Isolation ◽  
Iron Based

Abstract Despite of the importance of magnetism in possible relation to other key properties in iron-based superconductors, its understanding is still far from complete especially for FeSe systems. On one hand, the origin of the absence of magnetic orders in bulk FeSe is yet to be clarified. On the other hand, it is still not clear how close monolayer FeSe on SrTiO3, with the highest transition temperature among iron-based superconductors, is to a magnetic instability. Here we investigate magnetic properties of bulk and monolayer FeSe using dynamical mean-field theory combined with density-functional theory. We find that suppressed magnetic order in bulk FeSe is associated with the reduction of interorbital charge fluctuations, an effect of Hund’s coupling, enhanced by a larger crystal-field splitting. Meanwhile, spatial isolation of Fe atoms in expanded monolayer FeSe leads into a strong magnetic order, which is completely destroyed by a small electron doping. Our work provides a comprehensive understanding of the magnetic order in iron-based superconductors and other general multi-orbital correlated systems as Hund’s metals.

scholarly journals Glide-Plane Symmetry and Superconducting Gap Structure of Iron-Based Superconductors

2015 ◽  
Vol 114 (10) ◽  
Author(s):  
Y. Wang ◽  
T. Berlijn ◽  
P. J. Hirschfeld ◽  
D. J. Scalapino ◽  
T. A. Maier
Keyword(s):  
Superconducting Gap ◽  
Plane Symmetry ◽  
Iron Based Superconductors ◽  
Iron Based ◽  
Gap Structure

Superconducting Gap in s±-Wave Iron-Based Superconductors

SPIN ◽  
2018 ◽  
Vol 08 (02) ◽  
pp. 1850006
Author(s):  
B. Pradhan ◽  
S. K. Goi ◽  
R. N. Mishra
Keyword(s):  
Nearest Neighbor ◽  
Energy Gap ◽  
S Wave ◽  
Iron Based Superconductors ◽  
Model Study ◽  
Superconducting Energy Gap ◽  
Wave Symmetry ◽  
Iron Based ◽  
Double Time ◽  
Gap Parameter

We present a theoretical model study of superconductivity for iron-based high-[Formula: see text] superconductors in s[Formula: see text]-wave symmetry, considering two degenerate orbitals and the electron hopping up to the third nearest neighbor as a two-orbital model. The analytic expression for the temperature dependence of the superconducting order parameter is derived by Zubarev’s technique of double time single particle Green’s function method and solved self-consistently. The effect of inter orbital hopping on the superconducting energy gap parameter and electronic specific heat is studied.

Phenomenological theory for ±s-wave superconducting states of iron-based superconductors

2010 ◽  
Vol 470 ◽  
pp. S372-S374 ◽  
Author(s):  
M. Machida ◽  
Y. Nagai ◽  
Y. Ota ◽  
N. Nakai ◽  
H. Nakamura ◽  
...  
Keyword(s):  
Phenomenological Theory ◽  
S Wave ◽  
Iron Based Superconductors ◽  
Iron Based

A PROPOSED NEW MEASUREMENT OF THE SUPERCONDUCTING GAP IN YBa2Cu3O7

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3290-3293 ◽  
Author(s):  
G. L. ZHAO ◽  
D. BAGAYOKO
Keyword(s):  
Fermi Surface ◽  
Density Functional ◽  
Energy Gap ◽  
Interaction Matrix ◽  
Superconducting Gap ◽  
S Wave ◽  
Minor Variation ◽  
High Tc ◽  
Symmetry Properties ◽  
Superconducting Energy Gap

The superconducting energy gap of YBa 2 Cu 3 O 7 (YBCO) varies strongly with [Formula: see text] and from a sheet of the Fermi surface to another. The strong anisotropic superconducting gap in high Tc materials such as YBCO has led to conflicting d-wave and s-wave interpretations. We have utilized electronic wave functions from the ab-initio density functional calculation and the related electron-phonon interaction matrix elements for the calculation of the superconducting gap values of YBCO. We have found that the superconducting gap on one sheet of the Fermi surface around S-point only shows a minor variation from about 18 meV to 25 meV. Especially, there is no node on this sheet of the Fermi surface around the S-point. We propose a new test measurement of the superconducting gap of YBCO on this sheet of the Fermi surface around the S-point in the Brillouin zone. This measurement is expected to shed light on the gap symmetry properties of high Tc superconductors.

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