Symmetry, magnetism and superconductivity in new materials

这个建议涉及磁性和超导晶体与外来的，对称衍生的性质。在高温下，有序的非磁性晶体具有以下对称性：时间反转（即无论时间向前或向后移动，晶体都是一样的）；各种离散的旋转（例如，一个立方晶体如果旋转90度看起来是一样的）；和离散平移（当在原子尺度上观察时，晶体可以移动与晶体单元尺寸相对应的微小距离）。磁性晶体的时间反转对称性被打破，这意味着磁化的方向取决于时间的方向。除了时间反转对称性破缺之外，其他对称性也可能被破缺。在超导体中，一种更复杂的对称——规范对称——被打破了。这也可能伴随着其他类型的对称性破坏，包括时间反转对称性的破坏。

This proposal concerns magnetic and superconducting crystals with exotic, symmetry-derived properties. At high temperatures, an ordered, non-magnetic crystal possesses the following symmetries: time reversal (i.e. the crystal appears the same whether time runs forward or backwards); various discrete rotations (for example, a cubic crystal looks the same if turned by 90 degrees); and discrete translations (when viewed on an atomic scale, the crystal can be moved a tiny distance corresponding to the size of the crystal unit cell). Time reversal symmetry is broken in magnetic crystals, which means that the direction of the magnetisation depends on the direction of time. In addition to time reversal symmetry breaking, other symmetries may be broken as well. In superconductors, a more complicated kind of symmetry, called gauge symmetry, is broken. This may also be accompanied by other kinds of symmetry-breaking, including broken time reversal symmetry.