Effects of disorder and hydrostatic pressure on charge density wave and superconductivity in $2H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$

Effects of disorder and hydrostatic pressure on charge density wave and superconductivity in $2 H − {TaS}_{2}$

Shuxiang Xu, Jingjing Gao, Ziyi Liu, Keyu Chen, Pengtao Yang, Shangjie Tian, Chunsheng Gong, Jianping Sun, Mianqi Xue, Jun Gouchi, Xuan Luo, Yuping Sun, Yoshiya Uwatoko, Hechang Lei, Bosen Wang, and Jinguang Cheng

Phys. Rev. B 103, 224509 – Published 4 June 2021

Abstract

We report the comparative effects of disorder and hydrostatic pressure on charge density wave (CDW) and superconductivity (SC) in $2 H − {TaS}_{2}$ by measuring electrical resistivity and ac magnetic susceptibility. For the crystals in the clean limit (low disorder level), CDW ground state is suppressed completely at a critical pressure $P_{c} \sim 6.24 (5) GPa$ where a dome-shaped pressure dependence of superconducting transition temperature $T_{c}$ (P) appears with a maximum value of ${T_{c}}^{\max} \sim 9.15 K$ , indicating strong competitions between CDW and SC. The temperature exponent $n$ of low-temperature resistivity data decreases from ∼3.36 at ambient pressure (AP) to ∼1.29(2) at $P_{c}$ and then retains a saturated value ∼2.10(4) when the pressure is higher than 7.5 GPa; accordingly, the quadratic temperature coefficient of normal-state resistivity A peaks out just at $P_{c}$ with an enhancement by nearly one order in magnitude. These features strongly manifest that the enhanced critical CDW fluctuations near $P_{c}$ are possible important glues for superconducting pairings. High-pressure magnetic susceptibility indicates that superconducting shielding volume increases with pressure and retains a nearly constant value above $P_{c}$ , which evidences that the enhancement of $T_{c}$ (P) is accompanied by the expense of CDW. For those crystals in dirty limit (high disorder level), there is no clear CDW phase transition in resistivity; the pressure dependence of $T_{c}$ (P) and $n$ broadens up and becomes less apparent in comparison with the clean crystals. Our results suggest that disorder scattering and the melting of CDW are two factors affecting SC, and the melting of CDW dominates the change of $T_{c}$ below $P_{c}$ ; the enhancement of $T_{c}$ (P) is associated with the suppression of CDW by pressure and the increase in the density of states at Fermi level; however, after the CDW collapse, superconducting pairing strength is strongly weakened by impurity scattering above $P_{c}$ according to Anderson's theorem.

Received 3 November 2020
Revised 11 May 2021
Accepted 11 May 2021

DOI:https://doi.org/10.1103/PhysRevB.103.224509

Physics Subject Headings (PhySH)

Charge density waves Electrical properties Magnetic susceptibility Pressure effects Superconductivity

Pressure techniques

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Shuxiang Xu ^1,2,*, Jingjing Gao^3,4,*, Ziyi Liu¹, Keyu Chen^1,2, Pengtao Yang¹, Shangjie Tian ⁵, Chunsheng Gong⁵, Jianping Sun ^1,2, Mianqi Xue⁶, Jun Gouchi⁷, Xuan Luo^3,†, Yuping Sun^3,8,9, Yoshiya Uwatoko⁷, Hechang Lei^5,‡, Bosen Wang^1,2,10,§, and Jinguang Cheng ^1,2

¹Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
²School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
³Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
⁴Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China
⁵Department of Physics and Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
⁶Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, China
⁷Institute for Solid State Physics, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277–8581, Japan
⁸High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, China
⁹Collaborative Innovation Center of Microstructures, Nanjing University, Nanjing 210093, China
¹⁰Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China

^*The first two authors contributed equally.
^†Corresponding author: xluo@issp.ac.cn
^‡Corresponding author: hlei@ruc.edu.cn
^§Corresponding author: bswang@iphy.ac.cn

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Vol. 103, Iss. 22 — 1 June 2021

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Figure 1
(a) Temperature dependence of electrical resistivity ρ(T) for single-crystal $2 H − {TaS}_{2}$ (nos. S1–S8) with the measuring current parallel to the $a b$ plane of crystals; the back arrow indicates ICCDW phase transition of $2 H − {TaS}_{2}$ and is marked by $T_{ICCDW}$ ; (b) temperature dependence of the derivative $d ρ (T) / d T$ is plotted and $T_{CDW}$ is defined as the temperature with the $d ρ (T) / d T$ maximum; for comparison, the absolute $d ρ (T) / d T$ was shifted vertically; (c) the enlargement of low-T ρ(T)/ρ(300 K) ( $0 \leq T \leq 8 K$ ), where ρ(300 K) represents electrical resistivity at 300 K. The dependence of characteristic parameters on the residual resistivity ratio RRR $[= ρ (300 K) / ρ_{0}]$ ; (d) the residual resistivity $ρ_{0}$ ; $ρ_{0}$ was estimated by fitting the formula $ρ = ρ_{0} + A T^{n}$ and ICCDW phase transition temperature $T_{ICCDW}$ . The dashed lines indicate the changing tendency.
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Figure 2
ρ(T) under various pressures with the current parallel to $a b$ plane of crystals: (a) $2 H − {TaS}_{2}$ (no. S1) in PCC up to 2.06 GPa; (b) $2 H − {TaS}_{2}$ (no. S1) in CAC apparatus up to 12.5 GPa for run 1; (c) $2 H − {TaS}_{2}$ (no. S8) in CAC up to 11.5 GPa. (d)–(f) Temperature dependence of $d ρ / d T$ for nos. S1 and S8, respectively. (g)–(i) The enlargement of low-T ρ(T); the black and red arrows indicate $T_{ICCDW}$ and zero resistivity temperature ${T_{c}}^{zero}$ , respectively. “CAC” is short for the cubic anvil pressure cell and “PCC” is the piston cylinder pressure cell.
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Figure 3
(a) Temperature dependence of superconducting shielding volume $4 π χ_{v} (T)$ at a fixed frequency under a modulation AC magnetic field which is parallel to $a b$ plane of crystals for no. S1. Blue arrows show superconducting transition temperature ${T_{c}}^{M}$ where $4 π χ_{v} (T)$ decreases to one-half of the saturation values at lower temperatures. Pressure dependence of the characteristic temperatures: (b) $T_{CDW}$ , ${T_{c}}^{M}$ , and ${T_{c}}^{zero}$ ; (c) $4 π χ_{v}$ ; the dashed lines indicate changing trends. Two different fittings are performed by $ρ = ρ_{0} + A T^{n}$ : the polynomial fitting for $T < 20 K$ gives $ρ_{0}$ and $n$ and (d) the linear fitting for $n = 2$ to low-temperature data give the value of parameter A. The solid lines across the data indicate the fitting results.
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Figure 4
Temperature-pressure phase diagram for (a) $2 H − {TaS}_{2}$ , no. S1 and (b) $2 H − {TaS}_{2}$ , no. S8, respectively. The changing colors describe the tendency of resistivity. The data points of Cu interaction are from Refs. [29, 30]. The black lines are the fitting results by $T_{ICCDW} = T (AP) {(1 − P / P_{c})}^{β}$ , where the T(AP), the $P_{c}$ , and the β represent the $T_{ICCDW}$ at AP, the critical pressure where $T_{CDW}$ reduces to zero, and the exponent $n$ characterizing the suppression of parameters, respectively. The red lines represent the changing trends in (a) and (b). Pressure dependence of parameters in the same scales for nos. S1 and S8: (c) $ρ_{0}$ , (d) A, (e) $n$ , and (f) $T_{c}$ . The lines across the data show the changing trends.
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Figure 5
Phase diagram of single-crystal $2 H − {TaS}_{2}$ in the temperature, pressure, the RRR value [defined as $ρ (300 K) / ρ_{0}$ ], and Cu intercalation. The dashed and solid lines indicate changing trends. The ${T_{c}}^{\max}$ is the highest superconducting phase transition temperature. “ICCDW” represents the incommensurate CDW phase transition and “SC” is the superconductivity, respectively.
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Physical Review B

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Effects of disorder and hydrostatic pressure on charge density wave and superconductivity in $2 H − {TaS}_{2}$

Shuxiang Xu, Jingjing Gao, Ziyi Liu, Keyu Chen, Pengtao Yang, Shangjie Tian, Chunsheng Gong, Jianping Sun, Mianqi Xue, Jun Gouchi, Xuan Luo, Yuping Sun, Yoshiya Uwatoko, Hechang Lei, Bosen Wang, and Jinguang Cheng

Phys. Rev. B 103, 224509 – Published 4 June 2021

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Physical Review B

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Effects of disorder and hydrostatic pressure on charge density wave and superconductivity in 2H−TaS2

Shuxiang Xu, Jingjing Gao, Ziyi Liu, Keyu Chen, Pengtao Yang, Shangjie Tian, Chunsheng Gong, Jianping Sun, Mianqi Xue, Jun Gouchi, Xuan Luo, Yuping Sun, Yoshiya Uwatoko, Hechang Lei, Bosen Wang, and Jinguang Cheng

Phys. Rev. B 103, 224509 – Published 4 June 2021

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Effects of disorder and hydrostatic pressure on charge density wave and superconductivity in $2 H − {TaS}_{2}$