Two-gap superconductivity in Ba_1-xK_xFe_2As_2: A complementary study of the magnetic penetration depth by \muSR and ARPES

TL;DR

This study combines R and ARPES techniques to investigate two-gap superconductivity in Ba_1-xK_xFe_2As_2, revealing anisotropic properties and confirming the presence of two distinct superconducting gaps.

Contribution

It demonstrates the complementary use of R and ARPES to accurately determine the two superconducting gaps and their temperature evolution in Ba_1-xK_xFe_2As_2.

Findings

Identification of two superconducting gaps consistent across techniques

Observation of anisotropic penetration depth and critical field behaviors

Confirmation of two-gap superconductivity in Ba_1-xK_xFe_2As_2

Abstract

We investigate the magnetic penetration depth \lambda in superconducting Ba_1-xK_xFe_2As_2 (T_c\simeq32K) with muon-spin rotation (\muSR) and angle-resolved photoemission (ARPES). Using \muSR, we find the penetration-depth anisotropy \gamma_\lambda=\lambda_c/\lambda_{ab} and the second-critical-field anisotropy \gamma_{H_c2} to show an opposite T-evolution below T_c. This dichotomy resembles the situation in the two-gap superconductor MgB_2. A two-gap scenario is also suggested by an inflection point in the in-plane penetration depth \lambda_ab around 7K. The complementarity of \muSR and ARPES allows us to pinpoint the values of the two gaps and to arrive to a remarkable agreement between the two techniques concerning the full T-evolution of \lambda_ab. This provides further support for the described scenario and establishes ARPES as a tool to assess macroscopic properties of the superconducting condensate.