Non-Universal Superconducting Gap Structure in Iron-Pnictides Revealed by Magnetic Penetration Depth Measurements
By: by Kenichiro Hashimoto
Contributors: SpringerLink (Online service)
Series: Springer Theses, Recognizing Outstanding Ph.D. Research
Publisher: Springer Japan; Imprint: Springer
Published: 2013
Place of publication: Tokyo
Language: eng
Format: [electronic resource] /
Number of pages: 125
ISBN-13: 9784431542940
Subjects: Quantum theory; Physics; Magnetism; Magnetic Materials Magnetism; Superconductivity Strongly Correlated Systems
Description: In this book the author presents two important findings revealed by high-precision magnetic penetration depth measurements in iron-based superconductors which exhibit high-transition temperature superconductivity up to 55 K: one is the fact that the superconducting gap structure in iron-based superconductors depends on a detailed electronic structure of individual materials, and the other is the first strong evidence for the presence of a quantum critical point (QCP) beneath the superconducting dome of iron-based superconductors.The magnetic penetration depth is a powerful probe to elucidate the superconducting gap structure which is intimately related to the pairing mechanism of superconductivity. The author discusses the possible gap structure of individual iron-based superconductors by comparing the gap structure obtained from the penetration depth measurements with theoretical predictions, indicating that the non-universal superconducting gap structure in iron-pnictides can be interpreted in the framework of A1g symmetry. This result imposes a strong constraint on the pairing mechanism of iron-based superconductors.The author also shows clear evidence for the quantum criticality inside the superconducting dome from the absolute zero-temperature penetration depth measurements as a function of chemical composition. A sharp peak of the penetration depth at a certain composition demonstrates pronounced quantum fluctuations associated with the QCP, which separates two distinct superconducting phases. This gives the first convincing signature of a second-order quantum phase transition deep inside the superconducting dome, which may address a key question on the general phase diagram of unconventional superconductivity in the vicinity of a QCP.
Table of contents: title: Introduction; title: Superconducting Gap Structure and Magnetic Penetration Depth; title: Iron-based Superconductors; title: Experimental Method; title: Superconducting Gap Structure and Quantum Critical Point in BaFe2(As1-xPx)2; title: Superconducting Gap Nodes in the Zone-centered Hole Bands of KFe2As2; title: Nodeless vs. Nodal Order Parameter in LiFeAs and LiFeP; title: Conclusions.