Observation of Fermi surface deformation in a dipolar quantum gas

Abstract

Aligning a magnetic atomic gas When a bunch of fermions get together, they obey the Pauli exclusion principle: No two fermions can be in the same quantum state. The fermions populate the available states, starting from those lowest in energy. The boundary between the empty and filled states is called the Fermi surface (FS). For cold gases of fermionic atoms in the lab, the FS is usually spherical. Now, Aikawa et al. observe the FS squishing in a gas of Er atoms, which behave like tiny magnets and align with their magnetic field environment. The squishing reflects the very directional interactions between the Er atoms. Science , this issue p. 1484