A Study of CDW state in alkali metals

1.准备：由于碱金属容易氧化，也容易与其他金属、石英和化学溶剂反应，因此我们必须小心处理碱金属。我们制作了一个相当大的手套箱，在里面我们可以发光的K金属单晶和密封的晶体在石英安瓿与He气体。2. SOR-X射线：在筑波的KEK光子工厂，我们测量了X射线在低温下使用3 He-4 He稀释冰箱。测量的最低温度为75 mK，将最低温度下的劳厄斑与液氮温度下的劳厄斑进行比较，发现某些指标的劳厄斑在最低温度下出现了卫星斑，并分裂成两个或两个以上的劳厄斑。3.磁化率：我们用SQUID磁强计测量了K金属在1.8 ~ 300 K之间的磁化率随温度的变化，在20 K以上，磁化率几乎与温度无关，但在20 K以下，磁化率开始随温度降低而降低。在10 K左右，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跃迁在费米能级处形成电子能隙所致，总之，我们的实验结果表明K金属中存在CDW态的可能性。

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.