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Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor.

Charnukha A, Thirupathaiah S, Zabolotnyy VB, Büchner B, Zhigadlo ND, Batlogg B, Yaresko AN, Borisenko SV - Sci Rep (2015)

Bottom Line: The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field.In this work we show that a prototypical compound of the 1111-type, SmFe(0.92)Co(0.08)AsO , is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions.We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors.

View Article: PubMed Central - PubMed

Affiliation: 1] Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany [2] Physics Department, University of California-San Diego,La Jolla, CA 92093, USA.

ABSTRACT
In the family of iron-based superconductors, LaFeAsO-type materials possess the simplest electronic structure due to their pronounced two-dimensionality. And yet they host superconductivity with the highest transition temperature Tc ≈ 55K. Early theoretical predictions of their electronic structure revealed multiple large circular portions of the Fermi surface with a very good geometrical overlap (nesting), believed to enhance the pairing interaction and thus superconductivity. The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field. In this work we show that a prototypical compound of the 1111-type, SmFe(0.92)Co(0.08)AsO , is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions. Such singularities dramatically affect the low-energy electronic properties of the material, including superconductivity. We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors.

No MeSH data available.


Related in: MedlinePlus

Superconducting energy gap in the bulk low-energy electronic band structure of SmFe 0.92Co0.08AsO.a,b, Energy-distribution curves in the bulk electronic structure at several temperatures in the superconducting (1 K to 18 K) and normal (21 K) state integrated over a finite momentum range as shown by thick black lines in the respective insets. The energy of the incident radiation was tuned to 30 eV and 35 eV in a and b respectively. The superconducting energy gaps extracted from a fit with the Dynes function (see discussion in the text) are indicated. c, Temperature dependence of the superconducting energy gap in b (empty circles) and a fit using the weak-coupling expression obtained in the Bardeen-Cooper-Schrieffer theory of superconductivity41, with  and Tc = 19 K (solid line).
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f3: Superconducting energy gap in the bulk low-energy electronic band structure of SmFe 0.92Co0.08AsO.a,b, Energy-distribution curves in the bulk electronic structure at several temperatures in the superconducting (1 K to 18 K) and normal (21 K) state integrated over a finite momentum range as shown by thick black lines in the respective insets. The energy of the incident radiation was tuned to 30 eV and 35 eV in a and b respectively. The superconducting energy gaps extracted from a fit with the Dynes function (see discussion in the text) are indicated. c, Temperature dependence of the superconducting energy gap in b (empty circles) and a fit using the weak-coupling expression obtained in the Bardeen-Cooper-Schrieffer theory of superconductivity41, with and Tc = 19 K (solid line).

Mentions: Having established the bulk electronic structure of the optimally doped SmFe0.92Co0.08AsO we would like to note that superconductivity will develop on a very singular electronic landscape. Therefore, it is important to determine the momentum dependence of the superconducting energy gap throughout the Brillouin zone. To this end, we have carried out detailed high-resolution measurements of the temperature dependence of the photoemission intensity in the vicinity of both the Γ and M points of the Brillouin zone. The results of these measurements are presented in Fig. 3a,b in the form of energy-distribution curves (EDC) at two characteristic temperatures: in the normal state at 21 K (magenta lines) and the superconducting state at 1 K (black lines). In Fig. 3b several intermediate temperatures are shown as well. The EDCs have been integrated over a finite momentum range (indicated schematically with black lines in the insets of the respective panels) to facilitate the extraction of the superconducting energy gap from experimental data with finite energy and momentum resolution, as described in Ref. 22. Even without modeling, these raw integrated data reveal the presence of a superconducting energy gap manifested in the shift of the leading-edge of the EDC curves at the Fermi wave vector kF. It is known, however, that the leading-edge shift deviates from the value of the superconducting energy gap due to finite experimental resolution22. Therefore, the value of the superconducting energy gap has been extracted by fitting the momentum-integrated EDCs in Fig. 3 with the Dynes function multiplied by the Fermi function and convolved with the response function:


Interaction-induced singular Fermi surface in a high-temperature oxypnictide superconductor.

Charnukha A, Thirupathaiah S, Zabolotnyy VB, Büchner B, Zhigadlo ND, Batlogg B, Yaresko AN, Borisenko SV - Sci Rep (2015)

Superconducting energy gap in the bulk low-energy electronic band structure of SmFe 0.92Co0.08AsO.a,b, Energy-distribution curves in the bulk electronic structure at several temperatures in the superconducting (1 K to 18 K) and normal (21 K) state integrated over a finite momentum range as shown by thick black lines in the respective insets. The energy of the incident radiation was tuned to 30 eV and 35 eV in a and b respectively. The superconducting energy gaps extracted from a fit with the Dynes function (see discussion in the text) are indicated. c, Temperature dependence of the superconducting energy gap in b (empty circles) and a fit using the weak-coupling expression obtained in the Bardeen-Cooper-Schrieffer theory of superconductivity41, with  and Tc = 19 K (solid line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4441009&req=5

f3: Superconducting energy gap in the bulk low-energy electronic band structure of SmFe 0.92Co0.08AsO.a,b, Energy-distribution curves in the bulk electronic structure at several temperatures in the superconducting (1 K to 18 K) and normal (21 K) state integrated over a finite momentum range as shown by thick black lines in the respective insets. The energy of the incident radiation was tuned to 30 eV and 35 eV in a and b respectively. The superconducting energy gaps extracted from a fit with the Dynes function (see discussion in the text) are indicated. c, Temperature dependence of the superconducting energy gap in b (empty circles) and a fit using the weak-coupling expression obtained in the Bardeen-Cooper-Schrieffer theory of superconductivity41, with and Tc = 19 K (solid line).
Mentions: Having established the bulk electronic structure of the optimally doped SmFe0.92Co0.08AsO we would like to note that superconductivity will develop on a very singular electronic landscape. Therefore, it is important to determine the momentum dependence of the superconducting energy gap throughout the Brillouin zone. To this end, we have carried out detailed high-resolution measurements of the temperature dependence of the photoemission intensity in the vicinity of both the Γ and M points of the Brillouin zone. The results of these measurements are presented in Fig. 3a,b in the form of energy-distribution curves (EDC) at two characteristic temperatures: in the normal state at 21 K (magenta lines) and the superconducting state at 1 K (black lines). In Fig. 3b several intermediate temperatures are shown as well. The EDCs have been integrated over a finite momentum range (indicated schematically with black lines in the insets of the respective panels) to facilitate the extraction of the superconducting energy gap from experimental data with finite energy and momentum resolution, as described in Ref. 22. Even without modeling, these raw integrated data reveal the presence of a superconducting energy gap manifested in the shift of the leading-edge of the EDC curves at the Fermi wave vector kF. It is known, however, that the leading-edge shift deviates from the value of the superconducting energy gap due to finite experimental resolution22. Therefore, the value of the superconducting energy gap has been extracted by fitting the momentum-integrated EDCs in Fig. 3 with the Dynes function multiplied by the Fermi function and convolved with the response function:

Bottom Line: The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field.In this work we show that a prototypical compound of the 1111-type, SmFe(0.92)Co(0.08)AsO , is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions.We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors.

View Article: PubMed Central - PubMed

Affiliation: 1] Leibniz Institute for Solid State and Materials Research, IFW, 01069 Dresden, Germany [2] Physics Department, University of California-San Diego,La Jolla, CA 92093, USA.

ABSTRACT
In the family of iron-based superconductors, LaFeAsO-type materials possess the simplest electronic structure due to their pronounced two-dimensionality. And yet they host superconductivity with the highest transition temperature Tc ≈ 55K. Early theoretical predictions of their electronic structure revealed multiple large circular portions of the Fermi surface with a very good geometrical overlap (nesting), believed to enhance the pairing interaction and thus superconductivity. The prevalence of such large circular features in the Fermi surface has since been associated with many other iron-based compounds and has grown to be generally accepted in the field. In this work we show that a prototypical compound of the 1111-type, SmFe(0.92)Co(0.08)AsO , is at odds with this description and possesses a distinctly different Fermi surface, which consists of two singular constructs formed by the edges of several bands, pulled to the Fermi level from the depths of the theoretically predicted band structure by strong electronic interactions. Such singularities dramatically affect the low-energy electronic properties of the material, including superconductivity. We further argue that occurrence of these singularities correlates with the maximum superconducting transition temperature attainable in each material class over the entire family of iron-based superconductors.

No MeSH data available.


Related in: MedlinePlus