# LaCu$_{6-x}$Ag$_{x}$: A promising host of an elastic quantum critical point

## TL;DR

This study investigates LaCu$_{6-x}$Ag$_{x}$, revealing a continuous structural transition and evidence of an elastic quantum critical point, with transition temperatures suppressed by Ag doping.

## Contribution

The paper provides experimental evidence of an elastic quantum critical point in LaCu$_{6-x}$Ag$_{x}$ through diffraction and RUS measurements.

## Key findings

- Continuous orthorhombic to monoclinic transition observed.
- Structural transition temperature decreases with Ag doping.
- Quantum critical point identified at x_c = 0.225.

## Abstract

Structural properties of LaCu$_{6-x}$Ag$_{x}$ 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 LaCu$_{6-x}$Ag$_{x}$ 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 LaCu$_{6-x}$Ag$_{x}$.