Fermi Rubik's Cube in High-Pressure Induced Chlorine-Rich Compounds

In the quasi-free electron model, the Fermi surface spreads into a sphere in the Brillouin zone, i.e., the Fermi sphere. The Fermi sphere exists widely in metal systems, no matter whether the crystal is in a body-center cubic, face-center cubic, or hexagonal close-packed lattice. Here, we report a class of compounds stabilized at high pressure with Rubik's cubic Fermi surface, in which the representative example is Pm\bar3n-CaCl_3. Our quantum-mechanical variable-composition evolutionary simulations predict the thermal stabilities of CaCl_3, and the tight-binding model reveals that its unique Fermi surface originates from the quasi-one-dimensional interaction, structural symmetric protection, and particle-hole symmetry breaking. Furthermore, by its flat and steep band structure, CaCl_3 has a huge span of effective mass from 9.08\times 10^3 m_\rm e (super-heavy) to 5.13\times 10^-4 m_\rm e on the Fermi level, which supplies an interesting platform for quasiparticle research.