Unveiling charge density wave quantum phase transitions by x-ray diffraction

TL;DR

This study uses x-ray diffraction to explore how charge density wave transitions in certain intermetallic systems change as they approach a quantum critical point, revealing a crossover in critical behavior likely due to quantum fluctuations.

Contribution

It provides experimental evidence of a quantum critical point in charge density wave systems and shows a crossover from classical to mean-field critical behavior as T_CDW approaches zero.

Findings

Critical exponent crossover from 3D to mean-field behavior

Evidence of quantum fluctuations influencing phase transition

Presence of a quantum critical point at T_CDW = 0

Abstract

We investigate the thermal-driven charge density wave (CDW) transition of two cubic superconducting intermetallic systems Lu(Pt1-xPdx)2In and (Sr1-xCax)3Ir4Sn13 by means of x-ray diffraction technique. A detailed analysis of the CDW modulation superlattice peaks as function of temperature is performed for both systems as the CDW transition temperature T_CDW is suppressed to zero by an non-thermal control parameter. Our results indicate an interesting crossover of the classical thermal-driven CDW order parameter critical exponent from a three-dimensional universality class to a mean-field tendency, as T_CDW vanishes. Such behavior might be associated with presence of quantum fluctuations which influences the classical second-order phase transition, strongly suggesting the presence of a quantum critical point (QCP) at T_CDW = 0. This also provides experimental evidence that the effective dimensionality exceeds its upper critical dimension due to a quantum phase transition.