Geometric frustration · triangular lattice · competing exchange interactions
Geometric frustration arises when the lattice geometry prevents simultaneous minimization of all exchange interactions. On a triangular lattice with antiferromagnetic nearest-neighbor coupling J₁, no spin arrangement can satisfy all three bonds of a triangle simultaneously — at least one pair must be parallel. This macroscopic degeneracy leads to an extensive residual entropy (Wannier 1950: S/N = 0.3230 k_B per site), suppressed ordering, and exotic ground states. Adding a next-nearest-neighbor interaction J₂ further destabilizes order and can drive the system toward quantum spin liquid physics.