Three-state nematicity in the triangular lattice antiferromagnet Fe1/3NbS2

Abstract

Nematic order is the breaking of rotational symmetry in the presence of translational invariance. While originally defined in the context of liquid crystals, the concept of nematic order has arisen in crystalline matter with discrete rotational symmetry, most prominently in the tetragonal Fe-based superconductors where the parent state is four-fold symmetric. In this case the nematic director takes on only two directions, and the order parameter in such "Ising-nematic" systems is a simple scalar. Here, using a novel spatially-resolved optical polarimetry technique, we show that a qualitatively distinct nematic state arises in the triangular lattice antiferromagnet Fe1/3NbS2. The crucial difference is that the nematic order on the triangular lattice is a ℤ " , or three-state Potts-nematic order parameter. As a consequence, the anisotropy axes of response functions such as the resistivity tensor can be continuously re-oriented by external perturbations.This discovery provides insight into realizing devices that exploit analogies with nematic liquid crystals.

Half-magnetization plateau and the origin of threefold symmetry breaking in an electrically switchable triangular antiferromagnet

“…The existence of an UUUD half-magnetization plateau had previously been studied as a result of strong next nearest neighbor interactions within the triangular-lattice plane; we have determined that it is not limited to that case, as we see its emergence from strong interplanar interactions. The determination of these interactions and of the abnormally strong single-ion anisotropy has a large impact on the zero-field ground state of this material; the threefold symmetry breaking seen in optical measurements [9], for example, originates from a magnetic order driven by a large ratio of J 1c /J 1 ≈ 1/2, likely stripy in nature with a significant c-axis component. It is interesting to consider the implications for the electrical switching of the spin texture of this material.…”

“…At the center of this question is the nature of the magnetic ground state, which has been challenging to determine because collinear and noncollinear order are energetically close and the true ground state depends strongly on the magnetocrystalline anisotropy [6]. The nature of the underlying ordering in Fe 1/3 NbS 2 has been studied by both neutron scattering [7,8] of magnetic order and optical linear birefringence microscopy [9], which probes nematic structure in the electrical conductivity. Both measurements-electric and magnetic-find indications of threefold symmetry breaking in the ground state, whose origin is unclear.…”

Exchange bias due to coupling between coexisting antiferromagnetic and spin-glass orders

“…[21][22][23] Magnetization versus temperature measurements performed along the c-axis on x ≈ 1 3 , corresponding to the fully packed Fe 1/3 NbS 2 structure, we observe a sharp AFM transition with a Néel temperature of approximately 42 K (see supplement section 14) as has been previously reported. [20,22,[24][25][26] Above or below x = 1 3 , field cooled (FC) and zero field cooled (ZFC) curves begin to separate, indicating the presence of a frozen moment.…”

Magnetic structure investigation of the intercalated transition metal dichalcogenide V1/3NbS2

“…In this family of materials, magnetic atoms can be intercalated between the layers, and at the critical concentration of M 1/3 X S 2 , where M is a 3d transition metal, the compounds transform from the hexagonal centrosymmetric space group P6 3 /mmc to the hexagonal noncentrosymmetric chiral space group P6 3 22. The intercalated atoms occupy octahedral 2c or 2d Wyckoff positions [10] and form a superlattice of a kind determined by the stoichiometry of the material, with the M 1/3 X S 2 family hosting a √ 3 × √ 3 structure.…”