Superconductivity in the AIB_2-Type Ternary Rare-Earth Silicide YbGa_(1.1)Si_(0.9)

摘要

Superconductivity with a critical temperature (T_C) of 39 K, the highest T_C among intermetallics, was reported in MgB_2. MgB_2 crystallizes in a layered structure, that is, the AlB2-type (space group P6/mmm, No. 191, Z = 1), in which B atoms form honeycomb layers and Mg atoms are intercalated between the B layers. Because the layered structure plays a significant role in the superconductivity in MgB_2, a search for new layered superconducting materials was conducted. In this search, ternary silicides M_(AE)M_(TRx)Si_(2-x) (M_(AE) = Ca, Sr, and Ba, M_(TR) = Al and Ga) were found to be superconducting materials with AlB_2-type or its derivative structures. Figure 1 illustrates the crystal structure of the AlB_2-type M_(AE)M_(TRx)-Si_(2-x), in which M_(TR) and Si atoms form honeycomb layers and M_(AE) atoms are intercalated between the honeycomb layers.