The nature and value of the order parameters OPs in the superconducting Fe-based oxypnictides REFeAsO1−xFx RE=rare earth are a matter of intense debate, also connected to the pairing mechanism which is probably unconventional. Point-contact Andreev-reflection experiments on LaFeAsO1−xFx gave us direct evidence of three energy scales in the superconducting state: a nodeless superconducting OP, 1=2.8–4.6 meV, which scales with the local Tc of the contact; a larger unconventional OP that gives conductance peaks at 9.8–12 meV, apparently closes below Tc and decreases on increasing the Tc of the contact; a pseudogaplike feature i.e., a depression in the conductance around zero bias that survives in the normal state up to T*=140 K close to the Néel temperature of the undoped compound, which we associate to antiferromagnetic spin fluctuations coexisting with superconductivity. These findings point toward a complex, unconventional nature of superconductivity in LaFeAsO1−xFx.

Coexistence of two order parameters and a pseudogaplike feature in the iron-based superconductor LaFeAsO1−xFx / Gonnelli, Renato; Daghero, Dario; Tortello, Mauro; Ummarino, Giovanni; Stepanov, V. A.; Kim, J. S.; Kremer, R. K.. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 79:(2009), pp. 184526-1-184526-11. [10.1103/PhysRevB.79.184526]

Coexistence of two order parameters and a pseudogaplike feature in the iron-based superconductor LaFeAsO1−xFx

GONNELLI, Renato;DAGHERO, Dario;TORTELLO, MAURO;UMMARINO, Giovanni;
2009

Abstract

The nature and value of the order parameters OPs in the superconducting Fe-based oxypnictides REFeAsO1−xFx RE=rare earth are a matter of intense debate, also connected to the pairing mechanism which is probably unconventional. Point-contact Andreev-reflection experiments on LaFeAsO1−xFx gave us direct evidence of three energy scales in the superconducting state: a nodeless superconducting OP, 1=2.8–4.6 meV, which scales with the local Tc of the contact; a larger unconventional OP that gives conductance peaks at 9.8–12 meV, apparently closes below Tc and decreases on increasing the Tc of the contact; a pseudogaplike feature i.e., a depression in the conductance around zero bias that survives in the normal state up to T*=140 K close to the Néel temperature of the undoped compound, which we associate to antiferromagnetic spin fluctuations coexisting with superconductivity. These findings point toward a complex, unconventional nature of superconductivity in LaFeAsO1−xFx.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11583/2278076
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