5 research outputs found
Iron pnictides as a new setting for quantum criticality
Two major themes in the physics of condensed matter are quantum critical
phenomena and unconventional superconductivity. These usually occur in the
context of competing interactions in systems of strongly-correlated electrons.
All this interesting physics comes together in the behavior of the recently
discovered iron pnictide compounds that have generated enormous interest
because of their moderately high-temperature superconductivity. The ubiquity of
antiferromagnetic ordering in their phase diagrams naturally raises the
question of the relevance of magnetic quantum criticality, but the answer
remains uncertain both theoretically and experimentally. Here we show that the
undoped iron pnictides feature a novel type of magnetic quantum critical point,
which results from a competition between electronic localization and
itinerancy. Our theory provides a mechanism to understand the
experimentally-observed variation of the ordered moment among the undoped iron
pnictides. We suggest P substitution for As in the undoped iron pnictides as a
means to access this new example of magnetic quantum criticality in an unmasked
fashion. Our findings point to the iron pnictides as a much-needed new setting
for quantum criticality, one that offers a new set of control parameters.Comment: (v3) New abstract, more explanatory material, accepted for PNA
A Twisted Ladder: relating the Fe superconductors to the high cuprates
We construct a 2-leg ladder model of an Fe-pnictide superconductor and
discuss its properties and relationship with the familiar 2-leg cuprate model.
Our results suggest that the underlying pairing mechanism for the Fe-pnictide
superconductors is similar to that for the cuprates.Comment: 5 pages, 4 figure
Point-Contact Spectroscopy of Iron-Based Layered Superconductor LaOFFeAs
We present point-contact spectroscopy data for junctions between a normal
metal and the newly discovered F-doped superconductor
LaOFFeAs (F-LaOFeAs). A zero-bias conductance peak was
observed and its shape and magnitude suggests the presence of Andreev bound
states at the surface of F-LaOFeAs, which provides a possible evidence of an
unconventional pairing symmetry with a nodal gap function. The maximum gap
value meV was determined from the measured spectra,
in good agreement with the recent experiments on specific heat and lower
critical field.Comment: 5 pages, 4 figure