Study of the energy gap structure in iron-based superconductors using London penetration depth and controlled artificial disorder

This research work focuses on the theoretical investigation of the upper critical magnetic field,HC2; Ginzburg-Landau coherence length,ξGL(T); and Ginzburg-Landau penetration depth,λGL(T), for the two-band iron based superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs, we obtained expressions for the upper critical magnetic field,HC2; GL coherence length,ξGL; and GL penetration depth,λGL, as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel,HC2∥c, and perpendicular,HC2⊥c, to the symmetry axis (c-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field,HC2versus the angleθ. Similarly, the phase diagrams of the GL coherence length,ξGL, and GL penetration depth,λGL, parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations.

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

Physical Review Letters ◽

10.1103/physrevlett.114.107002 ◽

2015 ◽

Vol 114 (10) ◽

Cited By ~ 16

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

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Energy gap evolution across the superconductivity dome in single crystals of (Ba1−xKx)Fe2As2

Science Advances ◽

10.1126/sciadv.1600807 ◽

2016 ◽

Vol 2 (9) ◽

pp. e1600807 ◽

Cited By ~ 33

Author(s):

Kyuil Cho ◽

Marcin Kończykowski ◽

Serafim Teknowijoyo ◽

Makariy A. Tanatar ◽

Yong Liu ◽

...

Keyword(s):

Single Crystals ◽

Abrupt Change ◽

Energy Gap ◽

Superconducting Transition ◽

London Penetration Depth ◽

Wave State ◽

Iron Based Superconductors ◽

Optimal Doping ◽

Gap Anisotropy ◽

Materials Research

The mechanism of unconventional superconductivity in iron-based superconductors (IBSs) is one of the most intriguing questions in current materials research. Among non-oxide IBSs, (Ba1−xKx)Fe2As2has been intensively studied because of its high superconducting transition temperature and fascinating evolution of the superconducting gap structure from being fully isotropic at optimal doping (x≈ 0.4) to becoming nodal atx> 0.8. Although this marked evolution was identified in several independent experiments, there are no details of the gap evolution to date because of the lack of high-quality single crystals covering the entire K-doping range of the superconducting dome. We conducted a systematic study of the London penetration depth, λ(T), across the full phase diagram for different concentrations of point-like defects introduced by 2.5-MeV electron irradiation. Fitting the low-temperature variation with the power law, Δλ ~Tn, we find that the exponentnis the highest and theTcsuppression rate with disorder is the smallest at optimal doping, and they evolve with doping being away from optimal, which is consistent with increasing gap anisotropy, including an abrupt change aroundx≃ 0.8, indicating the onset of nodal behavior. Our analysis using a self-consistentt-matrix approach suggests the ubiquitous and robust nature ofs±pairing in IBSs and argues against a previously suggested transition to ad-wave state nearx= 1 in this system.

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Superconducting Gap in s±-Wave Iron-Based Superconductors

SPIN ◽

10.1142/s2010324718500066 ◽

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.

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Vortex structures, penetration depth and pairing in iron-based superconductors studied by small-angle neutron scattering

Reports on Progress in Physics ◽

10.1088/0034-4885/74/12/124504 ◽

2011 ◽

Vol 74 (12) ◽

pp. 124504 ◽

Cited By ~ 25

Author(s):

M R Eskildsen ◽

E M Forgan ◽

H Kawano-Furukawa

Keyword(s):

Neutron Scattering ◽

Penetration Depth ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Vortex Structures ◽

Iron Based Superconductors ◽

Iron Based

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Anisotropic London penetration depth and superfluid density in single crystals of iron-based pnictide superconductors

Physica C Superconductivity ◽

10.1016/j.physc.2009.03.012 ◽

2009 ◽

Vol 469 (9-12) ◽

pp. 582-589 ◽

Cited By ~ 46

Author(s):

R. Prozorov ◽

M.A. Tanatar ◽

R.T. Gordon ◽

C. Martin ◽

H. Kim ◽

...

Keyword(s):

Single Crystals ◽

Penetration Depth ◽

Superfluid Density ◽

London Penetration Depth ◽

Pnictide Superconductors ◽

Iron Based

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p-wave superconductivity in iron-based superconductors

Scientific Reports ◽

10.1038/s41598-019-50687-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 6

Author(s):

E. F. Talantsev ◽

K. Iida ◽

T. Ohmura ◽

T. Matsumoto ◽

W. P. Crump ◽

...

Keyword(s):

Energy Gap ◽

Atomic Layer ◽

P Wave ◽

Physical Parameters ◽

Superconducting Transition ◽

Iron Based Superconductors ◽

Wave Pairing ◽

Superconducting Energy Gap ◽

Wave States ◽

Iron Based

Abstract The possibility of p-wave pairing in superconductors has been proposed more than five decades ago, but has not yet been convincingly demonstrated. One difficulty is that some p-wave states are thermodynamically indistinguishable from s-wave, while others are very similar to d-wave states. Here we studied the self-field critical current of NdFeAs(O,F) thin films in order to extract absolute values of the London penetration depth, the superconducting energy gap, and the relative jump in specific heat at the superconducting transition temperature, and find that all the deduced physical parameters strongly indicate that NdFeAs(O,F) is a bulk p-wave superconductor. Further investigation revealed that single atomic layer FeSe also shows p-wave pairing. In an attempt to generalize these findings, we re-examined the whole inventory of superfluid density measurements in iron-based superconductors and show quite generally that single-band weak-coupling p-wave superconductivity is exhibited in iron-based superconductors.

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