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A small in-plane external uniaxial pressure has been widely used as an effective method to acquire single domain iron pnictide BaFe2As2, which exhibits twin-domains without uniaxial strain below the tetragonal-to-orthorhombic structural (nematic) transition temperature Ts. Although it is generally assumed that such a pressure will not affect the intrinsic electronic/magnetic properties of the system, it is known to enhance the antiferromagnetic (AF) ordering temperature TN (

The transport behavior at the quantum limit may show exotic phenomena such as special interlayer quantum transport. Here, the authors observe negative interlayer magnetoresistance resulted from tunneling of Dirac fermions between the zeroth Landau levels in BaGa2, indicating a feature at the quantum limit.

Exotic chiral fermions beyond Weyl fermions have recently been discovered in a series of chiral crystals such as CoSi. Here, the authors report the evidences of chiral fermions in RhSn with opposite handedness compared to those observed in CoSi, where the structural chirality is also opposite.

The interplay between the low-energy carriers in Dirac materials and magnetism is likely to reveal many novel physical phenomena. Here, the authors use two-magnon Raman scattering to determine the exchange energies of two prototypical magnetic Dirac systems, CaMnBi2 and SrMnBi2.

A small in-plane external uniaxial pressure has been widely used as an effective method to acquire single domain iron pnictide BaFe2As2, which exhibits twin-domains without uniaxial strain below the tetragonal-to-orthorhombic structural (nematic) transition temperature Ts. Although it is generally assumed that such a pressure will not affect the intrinsic electronic/magnetic properties of the system, it is known to enhance the antiferromagnetic (AF) ordering temperature TN (< Ts) and create in-plane resistivity anisotropy above Ts. Here we use neutron polarization analysis to show that such a strain on BaFe2As2 also induces a static or quasi-static out-of-plane (c-axis) AF order and its associated critical spin fluctuations near TN/Ts. Therefore, uniaxial pressure necessary to detwin single crystals of BaFe2As2 actually rotates the easy axis of the collinear AF order near TN/Ts, and such effects due to spin-orbit coupling must be taken into account to unveil the intrinsic electronic/magnetic properties of the system. BaFe2As2 is a parent compound for iron based superconductors, and this has motivated extensive study of its magnetic and electronics properties. Here, using neutron polarisation analysis, the authors demonstrate the critical importance of spin-orbit coupling to properties of BaFe2As2. [ABSTRACT FROM AUTHOR]

Dirac materials exhibit intriguing low-energy carrier dynamics that offer a fertile ground for novel physics discovery. Of particular interest is the interplay of Dirac carriers with other quantum phenomena such as magnetism. Here we report on a two-magnon Raman scattering study of AMnBi 2 (A=Ca, Sr), a prototypical magnetic Dirac system comprising alternating Dirac carrier and magnetic layers. We present the first accurate determination of the exchange energies in these compounds and, by comparison with the reference compound BaMn 2 Bi 2 , we show that the Dirac carrier layers in AMnBi 2 significantly enhance the exchange coupling between the magnetic layers, which in turn drives a charge-gap opening along the Dirac locus. Our findings break new grounds in unveiling the fundamental physics of magnetic Dirac materials, which offer a novel platform for probing a distinct type of spin-Fermion interaction. The results also hold great promise for applications in magnetic Dirac devices.