Pressure- and Composition-Induced Structural Quantum Phase Transition in the Cubic Superconductor (Sr, Ca)3Ir4Sn13

We show that the quasi-skutterudite superconductor Sr3Ir4Sn13 undergoes a structural transition from a simple cubic parent structure, the I phase, to a superlattice variant, the I' phase, which has a lattice parameter twice that of the high temperature phase. We argue that the superlattice distortion is associated with a charge density wave transition of the conduction electron system and demonstrate that the superlattice transition temperature T* can be suppressed to zero by combining chemical and physical pressure. This enables the first comprehensive investigation of a superlattice quantum phase transition and its interplay with superconductivity in a cubic charge density wave system. DOI: 10.1103/PhysRevLett.109.237008