Strain Tuning Three-state Potts Nematicity in a Correlated Antiferromagnet

Electron nematicity has become a familiar characteristic of many strongly correlated materials. A widely studied example is the discovered Ising-nematicity and its interplay with superconductivity in tetragonal iron pnictides. Since nematic directors in crystalline solids are restricted by the underlying crystal symmetry, recently emerged quantum matters with three-fold rotational symmetry offer a new platform to investigate nematic order with three-state Potts character. In this talk, we report reversible strain tuning of the three-state Potts nematicity in a zigzag antiferromagnet insulator, FePSe­₃. Probing the nematicity via optical linear dichroism, we demonstrate either 2π/3 or π/2 rotation of nematic director by uniaxial strain. The nature of the nematic phase transition can also be controlled such that it undergoes a smooth, crossover transition or a spontaneous Ising-like nematic flop transition. The ability to tune the nematic order with in-situ strain further enables the extraction of nematic susceptibility, which exhibits a divergent behavior near the magnetic ordering temperature.