TY - THES ID - 8360707 TI - Non-universal superconducting gap structure in iron-Pnictides revealed by magnetic penetration depth measurements PY - 2013 SN - 4431542930 4431542949 1299337643 PB - Tokyo ; New York : Springer, DB - UniCat KW - Superconductivity. KW - Superconductors -- Industrial applications. KW - Superconductors -- Research -- History. KW - Superconductivity KW - Iron-based superconductors KW - High temperature superconductors KW - Physics KW - Physical Sciences & Mathematics KW - Electricity & Magnetism KW - High temperature superconductors. KW - Physics. KW - Quantum physics. KW - Superconductors. KW - Magnetism. KW - Magnetic materials. KW - Strongly Correlated Systems, Superconductivity. KW - Quantum Physics. KW - Magnetism, Magnetic Materials. KW - Electric conductivity KW - Critical currents KW - Superfluidity KW - Materials at low temperatures KW - Superconductors KW - Quantum theory. KW - Mathematical physics KW - Electricity KW - Magnetics KW - Quantum dynamics KW - Quantum mechanics KW - Quantum physics KW - Mechanics KW - Thermodynamics KW - Materials KW - Superconducting materials KW - Superconductive devices KW - Cryoelectronics KW - Electronics KW - Solid state electronics UR - https://www.unicat.be/uniCat?func=search&query=sysid:8360707 AB - 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. ER -