Nature2014-06-26 4:28 PM

狄拉克磁单极子的实验观察 Observation of Dirac monopoles in a synthetic magnetic field

论文摘要 

自从狄拉克1931年建立了关于磁单极子的全面理论以来,物理学家就一直想把这些只有一个北极或一个南极的假想粒子分离出来。虽然磁单极子相似物已在自旋冰和其他奇异系统中被发现,但尚未有狄拉克磁单极子在一种由一个量子场所描述的介质内被直接观察到。但是现在,David Hall及同事报告了对在由一个自旋或“玻色-爱因斯坦”凝聚态所产生的人造磁场中的狄拉克磁单极子的实验观察。作者获得了在凝聚态内的涡线末端的单极子的真实空间图像,提供了证明狄拉克磁单极子之存在的证据。狄拉克磁单极子在一个受控环境中的生成和操纵为一系列实验和理论研究打开了大门。

Abstract 

Magnetic monopoles—particles that behave as isolated north or south magnetic poles—have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac’s 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin ices5, 6 and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3 (refs 10, 11, 12, 13). Here we demonstrate the controlled creation14 of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose–Einstein condensate. Monopoles are identified, in both experiments and matching numerical simulations, at the termini of vortex lines within the condensate. By directly imaging such a vortex line, the presence of a monopole may be discerned from the experimental data alone. These real-space images provide conclusive and long-awaited experimental evidence of the existence of Dirac monopoles. Our result provides an unprecedented opportunity to observe and manipulate these quantum mechanical entities in a controlled environment.

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