Order parameter fluctuation and ordering competition in Ba1−xKxFe2As2

Abstract

The competition among superconductivity, stripe-type magnetic order, and a new type of C4 symmetric magnetic order in Ba1−xKxFe2As2 is theoretically studied, focusing on its impact on the global phase diagram. By carrying out a renormalization group analysis of an effective field theory, we obtain the energy-scale dependent flows of all the model parameters, and then apply the results to understand the observed phase diagram. On the basis of the renormalization group analysis, we show that the critical line of nematic order has a negative slope in the superconducting dome and superconductivity is suppressed near the magnetic quantum critical point, which are both consistent with recent experiments. Moreover, we find that, although the observed C4 symmetric magnetic state could be a charge-spin density wave or a spin-vortex crystal at high temperatures, charge-spin density wave is the only stable C4 magnetic state in the low-temperature regime. Therefore, ordering competition provides a method to distinguish these two candidate C4 magnetic states.

Emergent Magnetic Degeneracy in Iron Pnictides due to the Interplay between Spin-Orbit Coupling and Quantum Fluctuations

“…Several microscopic mechanisms have been proposed to explain their origin [4,5,[25][26][27][28][29][30][31][32][33][34][35]. However, they generally suffer from two drawbacks.…”

Local structure of Mott insulating iron oxychalcogenides La2O2Fe2OM2(M=Karki1, Alfailakawi2, Frandsen3 et al. 2021Phys. Rev. B

“…We note that inquiry into the role of electronic nematicity has become the key focal point of the field of iron-based high-T c superconductivity. Future studies of short-range orthorhombic fluctuations, may provide information about the origin of electronic nematicity and its relation to the superconducting mechanism [34,38,[57][58][59][60][61][62].…”

Quantum criticality of fermion velocities and critical temperature nearby a putative quantum phase transition in the $d$-wave superconductors

“…1, we therefore ought to take discreetly into account the contributions from the interplay between the nodal QPs. On one hand, these nodal QPs themselves may mutually intertwine with each other owing to the strong fluctuations and become one of the major elements at the lowest-energy limit [65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98]104 . On the other hand, fermionic couplings can also impact other interaction parameters including fermion velocities v F,∆ and Yukawa coupling via participating in the coupled RG evolutions, which will be established in Sec.…”

“…After paralleling the strategy put forward in Refs. [99][100][101] , we integrate out the momentum shell within bΛ − Λ, where Λ is associated with the lattice constant to characterize the cutoff of energy scale and the variable parameter is designated as b = e −l with l > 0 being a running energy scale [17][18][19]21,22,48,68,69,75,104 , and eventually obtain (21) for Type-τ x order parameter. As to the other three types with M = τ y , τ z , τ 0 , the structures of their results are analogous to Eq.…”

“…However, quantum criticality would coax these nodal QPs to mutually intertwine with each other and influence fermion velocities plus Yukawa coupling. Consequently, fermion-fermion interactions may play important roles in determining critical behaviors around certain QCP [65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97][98]104 . Consequently, one can expect that uncovering the contributions from these two quantum critical ingredients may well improve our understandings on the quantum criticality of certain QCP in the d-wave superconductor.…”