报告题目：Pairing fermions with population imbalance

报 告 人：Prof. FULDE, Peter; Max Planck Institute for the Physics of Complex Systems

报告时间：2013年12月17日10:00

报告地点：物理系三楼报告厅

报告摘要：Cooper pairing of fermions starts usually from the premise that the two species forming pairs have equal populations, i.e., that their particle numbers are the same. That need not always be the case, though, and examples to the opposite are known. They concern superconducting metals, as well as dense quark matter, nuclear matter or ultra cold atoms.

The simplest case is that of a superconductor when a Zeeman term is added to the Hamiltonian. We will show that the Zeeman energy may result in breaking of translational invariance and hence in inhomogeneous superconducting ground states. Simple arguments will be presented which explain the origin of the symmetry breaking.

Experiments on CeCoIn5, and the two-dimensional organic superconductors κ -(BEDTTTF)₂•Cu(NCS)₂, λ-(BETS)₂FeCl₄, as well as cold atoms provide strong evidence that an inhomogeneous state is forming in high magnetic fields. However, the most important realization of inhomogeneous states is found in pi junctions, which seem to be on the verge of important technical applications. We will briefly describe progress which has been made here, based on ideas of Bulaevskii, Buzdin and others and realized by Ryazanovet al. and others.