Impurity and spin-fluctuation effects in an antiferromagnetic superconductors
We derive the superconducting density of states N/sub s/(..omega..) of an antiferromagnetic superconductor in the presence of impurities and spin fluctuations. We use a self-consistent ansatz for the Green's function G and our previous mean-field-theory results. N/sub s/(..omega..) depends on four functions of frequency: the renormalized frequency omega-tilde, gap Delta-tilde, molecular field H/sub Q/, and ''pseudogap'' Omega-tilde. Equations for these four parameters are set up in general and solved for the case of elastically scattering impurities and spin fluctuations. In the absence of any disorder the density of states has structure at the gap frequency ..delta.. and at ..omega.. = ..delta.. +- H/sub Q/, where H/sub Q/ is the (screened) molecular field. Most of our numerical work for dirty superconductors is based on a ''quasi-three-dimensional'' approximation which appears to be reasonable, although it underestimates gaplessness and overestimates the strength of the subsidiary peaks at ..delta.. +- H/sub Q/. We find in this approximation that magnetic impurities behave as might be expected but that nonmagnetic impurities can make an antiferromagnetic (AF) superconductor gapless at moderate concentrations. As the concentration is increased still further, the nonmagnetic impurities ''screen'' out the molecular field, a gap reopens, and N/sub s/(..omega..) obtains its BCS value. In the process of solving for N/sub s/(w), we have simultaneously solved the self-consistent equations for ..delta.. (as well as H/sub Q/) as a function of temperature T for dirty superconductors. We find that both ..delta.. and the thermodynamic critical field H/sub c/ exhibit structure at the magnetic ordering temperature T/sub M/. As in the case of our previous mean-field-theory results, the behavior of H/sub c/ is similar to that of H/sub c/2, observed in the ternary compounds.
- Research Organization:
- The James Franck Institute and the Department of Physics, The University of Chicago, Chicago, Illinois 60637
- OSTI ID:
- 6571770
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 25:7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
SUPERCONDUCTORS
ANTIFERROMAGNETISM
ENERGY-LEVEL DENSITY
CRITICAL FIELD
ENERGY GAP
FLUCTUATIONS
GREEN FUNCTION
IMPURITIES
SELF-CONSISTENT FIELD
SPIN
ANGULAR MOMENTUM
FUNCTIONS
MAGNETIC FIELDS
MAGNETISM
PARTICLE PROPERTIES
VARIATIONS
656102* - Solid State Physics- Superconductivity- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena- (-1987)