Lacu6-Xagx: A Promising Host Of An Elastic Quantum Critical Point

Structural properties of LaCu6-xAgx have been investigated using neutron and x-ray diffraction, and resonant ultrasound spectroscopy (RUS) measurements. Diffraction measurements indicate a continuous structural transition from orthorhombic (Pnma) to monoclinic (P2(1)/c) structure. RUS measurements show softening of natural frequencies at the structural transition, consistent with the elastic nature of the structural ground state. The structural transition temperatures in LaCu6-xAgx decrease with Ag composition until the monoclinic phase is completely suppressed at x(c) = 0.225. All of the evidence is consistent with the presence of an elastic quantum critical point in LaCu6-xAgx.