Alessandro Narduzzo

The intrinsic electronic phase diagram of iron-oxypnictide superconductors

We present the first comprehensive derivation of the intrinsic electronic phase diagram of the iron-oxypnictide superconductors in the normal state based on the analysis of the electrical resistivity ρ of both LaFeAsO1- xFx and SmF eAsO1- xFx for a wide range of doping. Our data give clear-cut evidence for unusual normal-state properties in these new materials. In particular, the emergence of superconductivity at low doping levels is accompanied by distinct anomalous transport behavior in ρ of the normal state which is reminiscent of the spin-density wave (SDW) signature in the parent material. At higher doping levels ρ of LaFeAsO1- xFx shows a clear transition from this pseudogap-like behavior to Fermi-liquid–like behavior, mimicking the phase diagram of the cuprates. Moreover, our data reveal a correlation between the strength of the anomalous features and the stability of the superconducting phase. The pseudogap-like features become stronger in SmF eAsO1- xFx where superconductivity is enhanced and vanish when superconductivity is reduced in the doping region with Fermi-liquid–like behavior.

High-Field Pauli-Limiting Behavior and Strongly Enhanced Upper Critical Magnetic Fields near the Transition Temperature of an Arsenic-Deficient LaO0.9F0.1FeAs1-δ Superconductor

We report upper critical field Bc2(T) data for disordered (arsenic-deficient) LaO0.9F0.1FeAs1-delta in a wide temperature and magnetic field range up to 47 T. Because of the large linear slope of Bc2 approximately -5.4 to -6.6 T/K near Tc approximately 28.5 K, the T dependence of the in-plane Bc2(T) shows a flattening near 23 K above 30 T which points to Pauli-limited behavior with Bc2(0) approximately 63-68 T. Our results are discussed in terms of disorder effects within [corrected] unconventional superconducting pairings.

Angle-dependent magnetoresistance of the layered organic superconductor κ − ( ET ) 2 Cu ( NCS ) 2 : Simulation and experiment

The angle-dependences of the magnetoresistance of two different isotopic substitutions (deuterated and undeuterated) of the layered organic superconductor \kappa-(ET)2Cu(NCS)2 are presented. The angle dependent magnetoresistance oscillations (AMRO) arising from the quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces in this material are often confused. By using the Boltzman transport equation extensive simulations of the AMRO are made that reveal the subtle differences between the different species of oscillation. No significant differences are observed in the electronic parameters derived from quantum oscillations and AMRO for the two isotopic substitutions. The interlayer transfer integrals are determined for both isotopic substitutions and a slight difference is observed which may account for the negative isotope effect previously reported [1]. The success of the semi-classical simulations suggests that non-Fermi liquid effects are not required to explain the interlayer-transport in this system.

Upper critical field, penetration depth, and depinning frequency of the high-temperature superconductor LafeAsO0.9F0.1 studied by microwave surface impedance

Temperature-dependent and magnetic-field-dependent measurements of the microwave surface impedance of superconducting

Dimensionality-driven spin-flop transition in quasi-one-dimensional PrBa2Cu4O8

{\text{LaFeAsO}}_{0.9}{\text{F}}_{0.1}

Irradiation-Induced Confinement in a Quasi-One-Dimensional Metal

({T}_{c}\ensuremath{\approx}26\text{ }\text{K})

Violation of the isotropic mean free path approximation for overdoped La2−xSrxCuO4

reveal a very large upper critical field

Possible Coexistence of Local Itinerancy and Global Localization in a Quasi-One-Dimensional Conductor

({B}_{c2}\ensuremath{\approx}56\text{ }\text{T})

Violation of the isotropic-

and a large value of the depinning frequency