Observation of Cooper pairs in a mesoscopic two-dimensional Fermi gas.

The formation of strongly correlated fermion pairs is fundamental for the emergence of fermionic superfluidity and superconductivity. For instance, Cooper pairs made of two electrons of opposite spin and momentum at the Fermi surface of the system are a key ingredient of Bardeen-Cooper-Schrieffer (BCS) theory-the microscopic explanation of the emergence of conventional superconductivity. Understanding the mechanism behind pair formation is an ongoing challenge in the study of many strongly correlated fermionic systems.

Observation of Pauli Crystals.

The Pauli exclusion principle is a fundamental law underpinning the structure of matter. Because of their antisymmetric wave function, no two fermions can occupy the same quantum state. Here, we report on the direct observation of the Pauli principle in a continuous system of up to six particles in the ground state of a two-dimensional harmonic oscillator.