The Possibility of a Structural Quantum Critical Point in LaCu$_{6-x}$Au$_x$

Understanding the critical phenomena near a quantum critical point (QCP) has attracted a substantial interest from the condensed matter physics community. Despite this interest, QCPs involving the zero temperature termination of a continuous structural phase transition remain largely unexplored. Here, we study the structural properties of the LaCu$_{6-x}$Au$_x$ series, which appears to be an ideal candidate to exhibit a SQCP. The orthorhombic-monoclinic transition temperatures in LaCu$_{6-x}$Au$_x$ decrease with Au-composition until a complete suppression of the monoclinic phase occurs at the SQCP, $x = 0.3$. The lattice component of the low-temperature heat capacity exhibits a maximum at the critical concentration, providing a further indication of the presence of a SQCP in the LaCu$_{6-x}$Au$_x$ series.