Tuning the interplay between nematicity and spin fluctuations in NaLi FeAs superconductors.

Strong interplay of spin and charge/orbital degrees of freedom is the fundamental characteristic of the iron-based superconductors (FeSCs), which leads to the emergence of a nematic state as a rule in the vicinity of the antiferromagnetic state. Despite intense debate for many years, however, whether nematicity is driven by spin or orbital fluctuations remains unsettled. Here, by use of transport, magnetization, and As nuclear magnetic resonance (NMR) measurements, we show a striking transformation of the relationship between nematicity and spin fluctuations (SFs) in NaLi FeAs; For x ≤ 0.

Orbital selective Fermi surface shifts and mechanism of high T(c) superconductivity in correlated AFeAs (A=Li, Na).

Based on the dynamical mean field theory and angle resolved photoemission spectroscopy, we have investigated the mechanism of high T(c) superconductivity in stoichiometric LiFeAs. The calculated spectrum is in excellent agreement with the measured angle resolved photoemission spectroscopy. The Fermi surface (FS) nesting, which is predicted in the conventional density functional theory method, is suppressed due to the orbital-dependent correlation effect within the dynamical mean field theory method.

Realization of giant magnetoelectricity in helimagnets.

We show that low field magnetoelectric (ME) properties of helimagnets Ba0.5Sr1.5Zn2(Fe1-xAlx)12O22 can be efficiently tailored by the Al-substitution level.