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 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 [Formula: see text] or three-state Potts-nematic order parameter. As a consequence, the anisotropy axes of response functions such as the resistivity tensor can be continuously reoriented by external perturbations. This discovery lays the groundwork for devices that exploit analogies with nematic liquid crystals.

中文翻译：

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三角晶格反铁磁体Fe1 / 3NbS2中的三态向列性。

向列顺序是在平移不变的情况下破坏旋转对称性。虽然最初是在液晶的背景下定义的，但向列顺序的概念已经出现在具有离散旋转对称性的晶体中，其中最显着的是在母态为四重对称的四方铁基超导体中。在这种情况下，向列指向矢只沿两个方向运行，在这种“向列向列”系统中，阶数参数是一个简单的标量。在这里，我们使用空间分辨光学极化技术，显示了在定性上独特的向列态出现在三角晶格反铁磁体Fe1 / 3NbS2中。关键区别在于，三角形晶格上的向列顺序是[公式：请参见文本]或三态Potts-向列顺序参数。作为结果，诸如电阻率张量之类的响应函数的各向异性轴可以通过外部扰动不断地重新定向。这一发现为利用向列液晶进行类比的设备奠定了基础。