Coexistence of ferromagnetism, antiferromagnetism, and superconductivity in magnetically anisotropic (Eu,La)FeAs2

Materials with exceptional magnetism and superconductivity usually conceive emergent physical phenomena. Here, we investigate the physical properties of the (Eu,La)FeAs2 system with double magnetic sublattices. The parent EuFeAs2 shows anisotropy-associated magnetic behaviors, such as Eu-related moment canting and exchange bias. Through La doping, the magnetic anisotropy is enhanced with ferromagnetism of Eu2+ realized in the overdoped region, and a special exchange bias of the superposed ferromagnetic/superconducting loop revealed in Eu0.8La0.2FeAs2. Meanwhile, the Fe-related antiferromagnetism shows unusual robustness against La doping. Theoretical calculation and 57Fe Mössbauer spectroscopy investigation reveal a doping-tunable dual itinerant/localized nature of the Fe-related antiferromagnetism. The coexistence of the Eu-related ferromagnetism, Fe-related robust antiferromagnetism, and superconductivity is further revealed in Eu0.8La0.2FeAs2, providing a platform for further exploration of potential applications and emergent physics. Finally, an electronic phase diagram is established for (Eu,La)FeAs2 with the whole superconducting dome adjacent to the Fe-related antiferromagnetic phase, which is of benefit for seeking underlying clues to high-temperature superconductivity.

An electronic phase diagram of hole-doped BiCuSeO crystals determined by transport characterization under various growth conditions

Temperature-hole-concentration dependent electronic phase-diagram of BiCuSeO.

Electronic phase diagram of Fe1+yTe1−xSex revealed by magnetotransport measurements

Among the Fe-based superconductors, [Formula: see text] is unique in that its crystal structure is the simplest and the electron correlation level is the strongest, and thus it is important to investigate the doping [Formula: see text]-temperature [Formula: see text] phase diagram of this system. However, inevitably incorporated excess Fe currently prevents the establishment of the true phase diagram. We overcome the aforementioned significant problem via developing a new annealing method termed as “Te-annealing” wherein single crystals are annealed under Te vapor. Specifically, we conducted various magnetotransport measurements on Te-annealed superconducting [Formula: see text]. We observed that crossover from the incoherent to the coherent electronic state and opening of the pseudogap occurs at high temperatures ([Formula: see text]150 K for [Formula: see text]). This is accompanied by a more substantial pseudogap and the emergence of a phase with a multi-band nature at lower temperatures (below [Formula: see text] for [Formula: see text]) before superconductivity sets in. Based on the results, the third type electronic phase diagram in Fe-based high-[Formula: see text] superconductors is revealed.

Synthesis, structural, and electronic properties of Sr1−xCaxPdAs

.This work maps out the structural and electronic phase diagram of Sr1-xCaxPdAs, a unique family of layered intermetallic honeycomb phases in which the PdAs layers distort away from ideal hexagonal symmetry.

Constructing Electronic Phase Diagram for the Half-filled Hubbard Model with Disorder

The electronic phase diagram of strongly correlated systems with disorder is constructed using the typical-medium theory. For half-filled system, the combination of the linearized dynamical mean field theory and equation of motion approach allows to derive the explicit equations determining the boundary between the correlated metal, Mott insulator, and Anderson insulator phases. Our phase diagram is consistent with those obtained by the more sophisticated methods.