Quantum criticallity in charge density wave systems: An x-ray diffraction approach

Quantum phase transitions are a subject of great concernment in the condensed matter community. Over the past decades, many systems presenting an ordered state which can be suppressed by non-thermal parameters leading to quantum critical points (QCP) have been studied. Notably, studies of charge density waves (CDW) QCP’s are still few. At the present work, we have studied two cubic CDW compounds, Lu(Pt1−xPdx)2In and (Sr1−xCax)3Ir4Sn13, which are also superconductors. Using synchrotron x-ray diffraction, we probe the CDW superstructure peaks as a function of temperature and external non-thermal parameters. We observe that the CDW order parameter critical exponent increase from a three-dimensional universality class to the mean-field value as TCDW is suppressed. Such finding might be related to the presence of quantum fluctuations, indicating a QCP at TCDW = 0.