PHYSICAL REVIEW B 102, 144510 (2020) Interplay between charge density wave order and superconductivity in LaAuSb 2 under pressure F. Du , 1 H. Su, 1 S. S. Luo, 1 B. Shen , 1 Z. Y. Nie, 1 L. C. Yin , 1 Y. Chen, 1 R. Li, 1 M. Smidman, 1, 2 and H. Q. Yuan 1, 2, 3, 4 , * 1 Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China 2 Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou 310058, China 3 State Key Laboratory of Silicon Materials, Zhejiang University, Hangzhou 310058, China 4 Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China (Received 3 July 2020; accepted 21 September 2020; published 12 October 2020) We report superconductivity below T c = 0.64 K in the charge density wave (CDW) ordered material LaAuSb 2 , from measurements of the electrical resistivity, specific heat, and ac magnetic susceptibility. To investigate the interplay between superconductivity and CDW order in LaAuSb 2 , we measured the resistivity under pressures up to 2.0 GPa and constructed the temperature-pressure phase diagram. With the application of pressure, T c increases gradually before exhibiting a sudden jump at around 0.64 GPa, while the CDW order is suppressed to lower temperatures before abruptly vanishing at the same pressure. We suggest that the jump of T c may be due to the enhancement of the density of states with the closure of the CDW energy gap when CDW order is suppressed. On the other hand, the normalized upper critical field H c2 changes little with pressure, suggesting that orbital limiting is the dominant pair-breaking mechanism in LaAuSb 2 . DOI: 10.1103/PhysRevB.102.144510 I. INTRODUCTION The nature of the complex interplay between different coexisting electronic states in correlated systems remains an open topic in condensed matter physics. A prime example is the competition or coexistence between magnetic order and superconductivity (SC) in heavy fermions and iron pnic- tides [1–4]. In these systems, quantum critical points (QCPs) surrounded by a superconducting dome are revealed when the magnetic order is suppressed to zero temperature by nonther- mal parameters such as pressure, magnetic fields, and doping. The interplay between charge-density-wave (CDW) order and SC has also been of great interest [5–12] since their coexis- tence in some systems leads to similar phase diagrams to those of heavy fermion and iron pnictide systems with magnetism and SC. CDW order corresponds to a periodic modulation of the conduction electron density, which was initially found in low- dimensional materials [5,6]. The coexistence of CDW and SC has been reported in some systems, where SC is typically en- hanced upon the suppression of CDW order [5,6], which can be well understood from Bardeen-Cooper-Schrieffer (BCS) superconducting theory since the suppression of CDW order leads to a closure of the the CDW gap on the Fermi surface, and hence enhances the density of states at the Fermi level N (E F ). However, in some other cases, the interplay between CDW and SC is more complicated [7–12]. For instance, a CDW QCP is reported in Lu(Pt 1−x Pd x ) 2 In [9], where critical fluctuations are considered to play an important role in the en- hancement of T c . A clear difference between magnetic QCPs and CDW QCPs is that non-Fermi liquid behavior is usually * Corresponding author: hqyuan@zju.edu.cn absent in the case of the latter [9,10]. However, whether the superconducting dome is associated with the CDW QCP still remains controversial. For instance, the superconducting dome was found to be separate from the CDW QCP in pres- surized 1T-TiSe 2 [11]. Therefore, whether critical quantum fluctuations can promote SC in the vicinity of a CDW QCP still remains unresolved. LaAuSb 2 belongs to the LaT Sb 2 (T = Ag, Au, Cu) family crystallizing in the ZrCuSi 2 -type structure [13]. LaAgSb 2 ex- hibits two CDW transitions at T CDW1 = 207 K and T CDW2 = 186 K, while SC is absent down to 0.3 K [14,15]. Upon applying pressure, T CDW1 is suppressed to 120 K at around 2.12 GPa, without the emergence of SC [16]. On the other hand, no signature of CDW order is detected in LaCuSb 2 , and there is a superconducting transition at T c = 0.9K[17]. Recently, a CDW transition at T CDW ≈ 88 K was reported in LaAuSb 2 , together with the absence of SC down to 2 K [13]. However, whether there is a superconducting transition in LaAuSb 2 at lower temperatures still remains unknown. In addition, the lattice volume of LaAuSb 2 is smaller than LaAgSb 2 , but larger than LaCuSb 2 . These results suggest that pressure may significantly affect the charge density wave order and SC in LaT Sb 2 . In this work, we report the discovery of superconductivity with T c = 0.64 K in LaAuSb 2 at ambient pressure from measurements of the electrical resistivity, spe- cific heat, and ac magnetic susceptibility. Based on resistivity measurements under pressure up to 2.0 GPa, we construct the temperature-pressure phase diagram of LaAuSb 2 . II. EXPERIMENTAL METHODS Single crystals of LaAuSb 2 were synthesized using the self-flux method described in Ref. [13]. The heat capacity down to 0.35 K was measured using a Quantum Design 2469-9950/2020/102(14)/144510(5) 144510-1 ©2020 American Physical Society