Magnetricity: understanding and exploiting a new phenomenon

一个多世纪以来，电荷电流(电)一直主导着理论和应用物理学的大部分议程，但类似的磁现象从未被研究过，无论是实验上还是理论上。原因是磁荷电流被认为是不存在的。然而，在最近的一系列发展表明在一种被称为“自旋冰”的材料中存在磁荷之后，所有这一切都改变了。这种材料含有浮现的磁电荷或单极，它们可以流动形成相当于电或磁性的磁性。自旋冰的磁荷不是基本粒子，因此无法逃脱物质，但它们的行为在实际意义上确实像磁荷。这种类型的磁电荷对所有磁性材料都是常见的，但只有在自旋冰中，它才以近乎点状的准粒子(单极)的形式存在，这些粒子可以自由地传导磁流。自旋冰的磁单极子是迄今发现的凝聚态物质中紧急激发的最生动的例子，并具有直接与磁场耦合的附加吸引力。因此，它们不仅在基础物理层面上令人感兴趣，而且还具有潜在的应用(磁电子学)。当然，这还有很长的路要走，但原则上的证明将照亮令人兴奋的可能性。该项目的主要目的是了解磁性的基本物理学，以期控制磁流，观察电荷重新排列，并最终建造一个装置。为了做到这一点，我们将重点了解自旋冰中磁荷输运的基本性质，包括块状和薄膜形式。我们还将探索热压人工自旋冰阵列。

While electric charge currents (electricity) have dominated much of the agenda of pure and applied physics for more than a century, the analogous magnetic phenomenon has never been investigated, either experimentally or theoretically. The reason is that magnetic charge currents were thought not to exist. However all this has changed after a series of recent developments that have demonstrated the existence of magnetic charges in a type of material called `spin ice'. This material contains emergent magnetic charges or monopoles that may flow to form a magnetic equivalent of electricity or magnetricity . The magnetic charges of spin ice are not elementary particles, so cannot escape the material, but they do behave like magnetic charges in a practical sense. This type of magnetic charge is common to all magnetic materials, but it is only in spin ice that it exists in the form of nearly point-like quasiparticles (monopoles) that are free to conduct magnetic current. The magnetic monopoles of spin ice are the most vivid example of an emergent excitation in condensed matter yet discovered, and have the added attractive quality that they directly couple to the magnetic field. They are thus of interest not only at the level of basic physics, but also for potential applications ( magnetronics ). Of course this is a long way off but a proof of principle would illuminate the exciting possibilities. The main aims of the project are to understand the basic physics of magnetricity with a view to controlling the magnetic current, observing charge rearrangements and, ultimately, building a device. In order to do this we will focus on understanding the basic properties of magnetic charge transport in spin ice in both its bulk form and in the form of thin films. We will also explore thermalised artificial spin ice arrays.