Abstract
Recent experimental studies performed in the normal state of iron-based superconductors have discovered the existence of the $C_4$-symmetric (tetragonal) itinerant magnetic state. This state can be described as a spin density wave with two distinct magnetic vectors ${\vec Q}_1$ and ${\vec Q}_2$. Given an itinerant nature of magnetism in iron-pnictides, we develop a quasiclassical theory of tetragonal magnetic order in disordered three-band metal with anisotropic band structure. Within our model we find that the $C_4$-symmetric magnetism competes with the $C_2$-symmetric state with a single ${\vec Q}$ magnetic structure vector. Our main results is that disorder promotes tetragonal magnetic state which is in agreement with earlier theoretical studies.
Highlights
Quasiclassical approach to interacting many-body systems has proved to be a powerful tool in describing their transport and thermodynamic properties
Another example is the experimental observation of the spin-density-wave order which is characterized by two magnetic ordering vectors, Q1 and Q2, in various iron-based superconducting alloys [13,14,15,16,17,18,19,20]
Perhaps it is not too surprising that we found the values of m1 and m2 equal to each other within the error bars of the numerical calculations
Summary
Quasiclassical approach to interacting many-body systems has proved to be a powerful tool in describing their transport and thermodynamic properties. One example of such phenomena is an observation of the peak in the penetration depth in BaFe2(As1−xPx) as a function of phosphorus concentration [7,8,9,10], in Ba1−xKxFe2As2 as a function of potassium concentration [11] and, most recently in Ba(Fe1−xCox)2As2 as a function of cobalt concentration [12] Another example is the experimental observation of the spin-density-wave order which is characterized by two magnetic ordering vectors, Q1 and Q2, in various iron-based superconducting alloys [13,14,15,16,17,18,19,20]. Inspired by the earlier work on this problem, in this paper we use a slightly simplified version of the model introduced in reference [36] to formulate a quasiclassical theory of the double-Q state in iron-based superconductors.
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