4,113 research outputs found
Enhancement of by disorder in underdoped iron pnictides
We analyze how disorder affects the transition temperature of the
superconducting state in the iron pnictides. The conventional wisdom is
that should rapidly decrease with increasing inter-band non-magnetic
impurity scattering, but we show that this behavior holds only in the overdoped
region of the phase diagram. In the underdoped regime, where superconductivity
emerges from a pre-existing magnetic state, disorder gives rise to two
competing effects: breaking of the Cooper pairs, which tends to reduce ,
and suppression of the itinerant magnetic order, which tends to bring
up. We show that for a wide range of parameters the second effect wins, leading
to an increase of with disorder in the coexistence state. Our results
explain several recent experimental findings and provide another evidence for
-pairing in the iron pnictides.Comment: 5 pages, 3 figures; revised version accepted in PRB-R
Specific heat jump at superconducting transition in the presence of Spin-Density-Wave in iron-pnictides
We analyze the magnitude of the specific heat jump \Delta C at the
superconducting transition temperature T_c in the situation when
superconductivity develops in the pre-existing antiferromagnetic phase. We show
that \Delta C/T_c differs from the BCS value and is peaked at the tri-critical
point where this coexistence phase first emerges. Deeper in the magnetic phase,
the onset of coexistence, T_c, drops and \Delta C/T_c decreases, roughly as
\Delta C/T_c \propto T^2_c at intermediate T_c and exponentially at the lowest
T_c, in agreement with the observed behavior of \Delta C/T_c in iron-based
superconductors.Comment: 4+ pages, 3 figure
Magnetic penetration depth in disordered iron-based superconductors
We study the effect of disorder on the London penetration depth in iron-based
superconductors. The theory is based on a two-band model with
quasi-two-dimensional Fermi surfaces, which allows for the coexistence region
in the phase diagram between magnetic and superconducting states in the
presence of intraband and interband scattering. Within the quasiclassical
approximation we derive and solve Eilenberger's equations, which include a weak
external magnetic field, and provide analytical expressions for the penetration
depth in the various limiting cases. A complete numerical analysis of the
doping and temperature dependence of the London penetration depth reveals the
crucial effect of disorder scattering, which is especially pronounced in the
coexistence phase. The experimental implications of our results are discussed.Comment: 10 pages, 6 figure
- …