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

Abstract

We investigate the thermal-driven charge density wave (CDW) transition of two cubic superconducting intermetallic systems Lu(Pt 1−x Pd x) 2 In and (Sr 1−x Ca x) 3 Ir 4 Sn 13 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 nonthermal 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 the 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.

Order-Disorder Transitions in (Ca$_x$Sr$_{1-x}$)$_3$Rh$_4$Sn$_{13}$

“…In a previous report, machine learning on the same data sets showed that all the additional superlattice peaks below T s have a wavevector of ( 1 2 1 2 0) and its symmetry equivalents with respect to the Bragg peaks [17], in agreement with previous x-ray diffraction results [10,18]. Figure 2(a,b) shows superlattice peaks in the (HK plane for x = 0 at 30 K, which weaken in intensity and collapse above T s ∼ 130 K. At 150 K, there is evidence of diffuse scattering peaking at superlattice wavevectors from structural fluctuations above T s (Fig.…”

Interplay between charge density wave and superconductivity in multiband systems with interband Coulomb interaction

“…Then, the evolution of T SC under pressure is likely driven by the variation of N (E F ), with a sudden disappearance of CDW order, which indicates that there is a first-order structural transition suggesting the lack of a QCP in this material [54]. On the other hand, the cubic superconducting intermetallic systems Lu(Pt 1−x Pd x ) 2 In and (Sr 1−x Ca x ) 3 Ir 4 Sn 13 present second-order CDW phase transitions under chemical doping and pressure, respectively [56].…”

“…We are particularly interested in intermetallic compounds and their alloys [13], like the layered SCs SrPt 2 As 2 and LaPt 2 Si 2 [54,57], the cubic superconducting systems Lu(Pt 1−x Pd x ) 2 In and (Sr 1−x Ca x ) 3 Ir 4 Sn 13 [56], the cubic Heusler alloys Lu(Pt 1−x Pd x ) 2 In [3], and the large family of superconducting stannides with composition A 3 T 4 Sn 13 , where A = La; Sr; Ca and T = Rh; Ir [58]. These systems have in common a rather narrow d-band with moderate electronic correlations (as compared with the f -bands in heavy fermions, where a large U approach is necessary [59]) coexisting with large sp-bands [60].…”

Interplay between charge density wave and superconductivity in multi-band systems with inter-band Coulomb interaction

“…Then, the evolution of T SC under pressure is likely driven by the variation of N (E F ), with a sudden disappearance of CDW order, which indicates that there is a first-order structural transition suggesting the lack of a QCP in this material [54]. On the other hand, the cubic superconducting inter-metallic systems Lu(Pt 1−x Pd x ) 2 In and (Sr 1−x Ca x ) 3 Ir 4 Sn 13 present second-order CDW phase transitions, under chemical doping and pressure, respectively [56].…”

“…We are particularly interested in inter-metallic compounds and their alloys [13], like the layered SCs SrPt 2 As 2 and LaPt 2 Si 2 [54,57], the cubic superconducting systems Lu(Pt 1−x Pd x ) 2 In and (Sr 1−x Ca x ) 3 Ir 4 Sn 13 [56], the cubic Heusler alloys Lu(Pt 1−x Pd x ) 2 In [3], and the large family of superconducting stannides with composition A 3 T 4 Sn 13 , where A = La; Sr; Ca and T = Rh; Ir [58]. These systems have in common a rather narrow d-band with moderate electronic correlations (as compared with the f -bands in heavy fermions) coexisting with large sp-bands [59].…”