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.
View Article and Find Full Text PDFThe 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.
View Article and Find Full Text PDFMany-body physics describes phenomena that cannot be understood by looking only at the constituents of a system. Striking examples are broken symmetry, phase transitions and collective excitations. To understand how such collective behaviour emerges as a system is gradually assembled from individual particles has been a goal in atomic, nuclear and solid-state physics for decades.
View Article and Find Full Text PDFQuantum anomalies are violations of classical scaling symmetries caused by divergences that appear in the quantization of certain classical theories. Although they play a prominent role in the quantum field theoretical description of many-body systems, their influence on experimental observables is difficult to discern. In this study, we discovered a distinctive manifestation of a quantum anomaly in the momentum-space dynamics of a two-dimensional (2D) Fermi superfluid of ultracold atoms.
View Article and Find Full Text PDFThe nature of the normal phase of strongly correlated fermionic systems is an outstanding question in quantum many-body physics. We used spatially resolved radio-frequency spectroscopy to measure pairing energy of fermions across a wide range of temperatures and interaction strengths in a two-dimensional gas of ultracold fermionic atoms. We observed many-body pairing at temperatures far above the critical temperature for superfluidity.
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