A Study of CDW state in alkali metals

1.制备：由于碱金属容易氧化，也容易与其他金属、石英和化学溶剂发生反应，所以处理碱金属时一定要小心。我们做了一个相当大的手套箱，在里面我们可以发光K金属的单晶，并将晶体与He气体一起密封在石英瓶里。索尔- x射线：在位于筑波的KEK光子工厂，我们使用3He-4He稀释冰箱在低温下测量x射线。测量的最低温度为75℃。将在最低温度下测得的劳厄点与在液氮温度下测得的劳厄点进行比较，一些具有某些指标的劳厄点在最低温度下被卫星分割成两个或多个劳厄点。目前我们还不能断定这些现象是CDW转变的结果。磁化率：我们用SQUID磁力计测量了K金属在1.8 ~ 300K之间磁化率的温度依赖性。在20 K以上，磁化率几乎与温度无关，但在20 K以下，磁化率开始随着温度的降低而降低。在大约10k时，它下降得更快。目前我们还不知道这种磁化率的温度依赖性是否是由于CDW跃迁在费米能处形成电子能隙所致。综上所述，我们的实验结果提示了K金属中CDW态存在的可能性。

1.Preparation : Since the alkali metals are easily oxiclized and also easily react with other metals, quartz and chemical solvents, we must be careful to treat the alkali metals. We made a rather large glove box inside which we can glow the single crystals of K metal and seal the crystal inside the quartz ampule together with He gas.2.SOR-Xray : At the Photon Factory of KEK in Tsukuba, We measured the x-ray at low temperatures by using a 3He-4He dilution refrigerator. The lowest temperature of the measurements was 75 mK.Compared the Laue spots measured at the lowest temperature with one measured at the liquid Nitrogen temperature, some spots with some indexes has the satellite and split into two or more spots at the lowest temperature. At present we cannot conclude that these phenomena are resultant of the CDW transition.3.Magnetic susceptibility : We measured the temperature dependence of the magnetic susceptibility of K metal by using a SQUID magnetometer between 1.8 and 300K.Above 20 K the magnetic susceptibility is almost temperature independent, but below 20 K it starts to decrease with decreasing temperature. And at about 10 K it decreasing more rapidly. At present we do not know if this temperature dependence of the magnetic susceptibility is due to the forming the electronic energy gap at the Fermi energy by CDW transition.In conclusion our experimental results suggest the possibility of CDW state in K metal.