In this paper we report the impact of uniaxial strain $\varepsilon$ applied along the crystalline $a$ axis on the newly discovered kagome superconductor CsV$_3$Sb$_5$. At ambient conditions, CsV$_3$Sb$_5$ shows a charge-density wave (CDW) transition at $T_{\rm CDW}=94.5$ K and superconducts below $T_C = 3.34$ K. In our study, when the uniaxial strain $\varepsilon$ is varied from $-0.90\%$ to $0.90\%$, $T_C$ monotonically increases by $\sim 33\%$ from 3.0 K to 4.0 K, giving rise to the empirical relation $T_C (\varepsilon)=3.4+0.56\varepsilon+0.12\varepsilon^2$. On the other hand, for $\varepsilon$ changing from $-0.76\%$ to $1.26\%$, $T_{\rm CDW}$ decreases monotonically by $\sim 10\%$ from 97.5 K to 87.5 K with $T_{\rm CDW}(\varepsilon)=94.5-4.72\varepsilon-0.60\varepsilon^2$. The opposite response of $T_C$ and $T_{\rm CDW}$ to the uniaxial strain suggests strong competition between these two orders. Comparison with hydrostatic pressure measurements indicate that it is the change in the $c$-axis that is responsible for these behaviors of the CDW and superconducting transitions, and that the explicit breaking of the sixfold rotational symmetry by strain has a negligible effect. Combined with our first-principles calculations and phenomenological analysis, we conclude that the enhancement in $T_C$ with decreasing $c$ is caused primarily by the suppression of $T_{\rm CDW}$, rather than strain-induced modifications in the bare superconducting parameters. We propose that the sensitivity of $T_{\rm CDW}$ with respect to the changes in the $c$-axis arises from the impact of the latter on the trilinear coupling between the $M_1^+$ and $L_2^-$ phonon modes associated with the CDW. Overall, our work reveals that the $c$-axis lattice parameter, which can be controlled by both pressure and uniaxial strain, is a powerful tuning knob for the phase diagram of CsV$_3$Sb$_5$.
The recently discovered layered kagome metals AV$_3$Sb$_5$ (A = K, Rb, and Cs) with vanadium kagome networks provide a novel platform to explore correlated quantum states intertwined with topological band structures. Here we report the prominent effect of hole doping on both superconductivity and charge density wave (CDW) order, achieved by selective oxidation of exfoliated thin flakes. A superconducting dome is revealed as a function of the effective doping content. The superconducting transition temperature ($T_{\mathrm{c}}$) and upper critical field in thin flakes are significantly enhanced…
Strain-Tuned Nodal Superconductivity in the Charge-Ordered Kagome Metal CsV$_3$Sb$_5$
Okayama University（冈山大学）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Beijing National Laboratory for Condensed Matter Physics（北京凝聚态物理国家实验室）；Fujian Provincial Collaborative Innovation Center for Advanced High-Field Superconducting Materials and Engineering（福建省先进高场超导材料与工程协同创新中心）；College of Physics and Energy, Fujian Normal University（福建师范大学物理与能源学院）；Guang’an Institute of Technology
The recently discovered Kagome family ${\mathrm{AV}}_3{\mathrm{Sb}}_5$ (A = K, Rb, Cs) exhibits rich physical phenomena, including non-trivial topological electronic structure, giant anomalous Hall effect, charge density waves (CDW) and superconductivity. Notably, CDW in ${\mathrm{AV}}_3{\mathrm{Sb}}_5$ is evidenced to intertwine with its superconductivity and topology, but its nature remains elusive. Here, we combine x-ray scattering experiments and density-functional theory calculations to investigate the CDWs in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ and demonstrate the coexistence of 2 $\times$…
In kagome metals AV3Sb5 (A = K, Rb, Cs), three-dimensional charge order (3D-CO) is the primary instability that sets the stage for other collective orders to emerge, including unidirectional stripe order, orbital flux order, electronic nematicity, and superconductivity. Here, we use high-resolution angle-resolved photoemission spectroscopy to determine the microscopic structure of three-dimensional charge order (3D-CO) in AV3Sb5 and its interplay with superconductivity. Our approach is based on identifying an unusual splitting of kagome bands induced by 3D-CO, which provides a sensitive way to…
Superconductivity in topological kagome metals has recently received great research interests. Here, charge density wave (CDW) orders and the evolution of superconductivity under various pressures in CsV3Sb5 single crystal with V kagome lattice are investigated. By using high-resolution scanning tunnelling microscopy /spectroscopy (STM/STS), two CDW orders in CsV3Sb5 are observed which correspond to 4a*1a and 2a*2a superlattices. By applying pressure, the superconducting transition temperature Tc is significantly enhanced and reaches a maximum value of 8.2 K at around 1 GPa. Accordingly, CDW s…
The kagome metal CsV$_{3}$Sb$_{5}$ features an unusual competition between the charge-density-wave (CDW) order and superconductivity. Evidence for time-reversal symmetry breaking (TRSB) inside the CDW phase has been accumulating. Hence, the superconductivity in CsV$_{3}$Sb$_{5}$ emerges from a TRSB normal state, potentially resulting in an exotic superconducting state. To reveal the pairing symmetry, we first investigate the effect of nonmagnetic impurity. Our results show that the superconducting critical temperature is insensitive to disorder, pointing to conventional $s$-wave superconductiv…
High-resolution thermal-expansion and specific-heat measurements were performed on single crystalline BaFe2(As1-xPx)2 (0 < x < 0.33, x = 1). The observation of clear anomalies allows to establish the thermodynamic phase diagram which features a small coexistence region of SDW and superconductivity with a steep rise of Tc on the underdoped side. Samples that undergo the tetragonal-orthorhombic structural transition are detwinned in situ, and the response of the sample length to the magneto-structural and superconducting transitions is studied for all three crystallographic directions. It is sho…
Starting from the orthorhombic magnetically ordered phase, we investigate the effects of uniaxial tensile and compressive stresses along a, b, and the diagonal a+b directions in BaFe2As2 and CaFe2As2 in the framework of ab initio density functional theory (DFT) and a phenomonological Ginzburg-Landau model. While -contrary to the application of hydrostatic or c-axis uniaxial pressure- both systems remain in the orthorhombic phase with a pressure-dependent nonzero magnetic moment, we observe a sign-changing jump in the orthorhombicity at a critical uniaxial pressure, accompanied by a reversal of…
We study theoretically the shift of the superconducting transition temperature (Tc) under uniaxial compression in beta-type organic superconductors, beta-(BEDT-TTF)2I3 and beta-(BDA-TTP)2X[X=SbF6,AsF6], in order to clarify the electron correlation, the spin frustration and the effect of dimerization. The transfer integrals are calculated by the extended Huckel method assuming the uniaxial strain and the superconducting state mediated by the spin fluctuation is solved using Eliashberg's equation with the fluctuation-exchange approximation. The calculation is carried out on both the dimerized (o…
The kagome metals of the family $A$V$_3$Sb$_5$, featuring a unique structural motif, harbor an array of intriguing phenomena such as chiral charge order and superconductivity. CsV$_3$Sb$_5$ is of particular interest because it displays a double superconducting dome in the region of the temperature-pressure phase diagram where charge order is still present. However, the microscopic origin of such an unusual behavior remains an unsolved issue. Here, to address it, we combine high-pressure, low-temperature muon spin relaxation with first-principles calculations. We observe a pressure-induced thre…
The La-based '214' cuprates host several symmetry breaking phases including superconductivity, charge and spin order in the form of stripes, and a structural othorhombic-to-tetragonal phase transition. Therefore, these materials are an ideal system to study the effects of uniaxial stress onto the various correlations that pervade the cuprate phase diagram. We report resonant x-ray scattering experiments on $\textrm{La}_{1.475}\textrm{Nd}_{0.4}\textrm{Sr}_{0.125}\textrm{Cu}\textrm{O}_{4}$ (LNSCO-125) that reveal a significant response of charge stripes to uniaxial tensile-stress of $\sim$ 0.1 G…
Unified pressure and field response across distinct charge-order regimes in Ti-doped CsV$_3$Sb$_5$
PSI Center for Neutron and Muon Sciences（保罗谢尔研究所中子与μ子科学中心）；Materials Department and California Nanosystems Institute, University of California Santa Barbara（加州大学圣塔芭芭拉分校材料系及加州纳米系统研究院）；Physik-Institut, Universität Zürich（苏黎世大学物理学院）
Understanding the competition between superconductivity and other ordered states (such as antiferromagnetic or charge-density-wave (CDW) state) is a central issue in condensed matter physics. The recently discovered layered kagome metal AV3Sb5 (A = K, Rb, and Cs) provides us a new playground to study the interplay of superconductivity and CDW state by involving nontrivial topology of band structures. Here, we conduct high-pressure electrical transport and magnetic susceptibility measurements to study CsV3Sb5 with the highest Tc of 2.7 K in AV3Sb5 family. While the CDW transition is monotonical…
The interplay between charge-density-wave (CDW) order and superconductivity (SC) in the Kagome metal RbV3Sb5 is studied by tracking the evolutions of their transition temperatures, T* and Tc, as a function of pressure (P) via measurements of resistivity and magnetic susceptibility under various hydrostatic pressures up to ~ 5 GPa. It is found that the CDW order at T* experiences a subtle modification at Pc1 ~ 1.5 GPa before it is completely suppressed around Pc2 ~ 2.4 GPa. Accordingly, the superconducting transition Tc(P) exhibits a shallow M-shaped double superconducting dome with two extrema…
Structural symmetry effects on the competition of density waves and superconductivity in bilayer nickelates
Ruhr-Universität Bochum（波鸿鲁尔大学）；Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所（北京凝聚态物理国家研究中心））；School of Physical Sciences, University of Chinese Academy of Sciences（中国科学院大学物理科学学院）
Spontaneous symmetry breaking constitutes a paradigmatic classification scheme of matter. However, broken symmetry also entails domain degeneracy that often impedes identification of novel low symmetry states. In quantum matter, this is additionally complicated by competing intertwined symmetry breaking orders. A prime example is that of unconventional superconductivity and density-wave orders in doped cuprates in which their respective symmetry relation remains a key question. Using uniaxial pressure as a domain-selective stimulus in combination with x-ray diffraction, we unambiguously reveal…
Using strain to uncover the interplay between two- and three-dimensional charge density waves in high-temperature superconducting YBa$_{2}$Cu$_{3}$O$_{\rm{y}}$
We have used resonant x-ray scattering to determine the momentum dependent charge correlations in YBa$_2$Cu$_3$O$_{6.55}$ samples with highly ordered chain arrays of oxygen acceptors (ortho-II structure). The results reveal nearly critical, biaxial charge density wave (CDW) correlations at in-plane wave vectors (0.315, 0) and (0, 0.325). The corresponding scattering intensity exhibits a strong uniaxial anisotropy. The CDW amplitude and correlation length are enhanced as superconductivity is weakened by an external magnetic field. Analogous experiments were carried out on a YBa$_2$Cu$_3$O$_{6.6…
A chemical avenue to manipulate field-reentrant superconducting rivalries in infinite layer nickelates
University of Science and Technology Beijing（北京科技大学）；Beijing Normal University（北京师范大学）；Anhui University（安徽大学）；Center for High Pressure Science and Technology Advanced Research（高压科学与技术先进研究中心）；Institute for Shanghai Advanced Research in Physical Sciences (SHARPS)（上海物理科学前沿研究院）；Chinese Academy of Sciences（中国科学院）；North China Electric Power University（华北电力大学）；East China Normal University（华东师范大学）；PSI Center for Neutron and Muon Sciences（瑞士保罗谢勒研究所中子与缪子科学中心）
Based on first-principles simulations and calculations, we explore the evolution of crystal structure, electronic structure and transport properties of quasi 2D layered PdS2 under uniaxial stress and hydrostatic pressure. The coordination of the Pd ions plays crucial roles in the structural transition, electronic structure and transport properties of PdS2. An interesting ferroelastic phase transition with lattice reorientation is revealed under uniaxial compressive stress, which originates from the bond reconstructions of the unusual PdS4 square-planar coordination. By contrast, the layered st…
We discuss superconductivity in a model on a cubic lattice for a $Γ_3$ non-Kramers system. In previous studies, it is revealed that $d$-wave superconductivity with $E_g$ symmetry occurs in a wide parameter range in a $Γ_3$ system. Such anisotropic superconductivity can break the cubic symmetry of the lattice. In a $Γ_3$ system, the quadrupole degrees of freedom are active and the effect of the cubic symmetry breaking should be important. Here, we investigate the coexisting states of the $d$-wave superconductivity and quadrupole order by a mean-field theory. In particular, we discuss possible c…
A combined resistivity and hard x-ray diffraction study of superconductivity and charge ordering in $\mathrm{Ir_{1-x}Pt_xTe_2}$, as a function of Pt substitution and externally applied hydrostatic pressure, is presented. Experiments are focused on samples near the critical composition $x_c\sim 0.045$ where competition and switching between charge order and superconductivity is established. We show that charge order as a function of pressure in $\mathrm{Ir_{0.95}Pt_{0.05}Te_{2}}$ is preempted - and hence triggered - by a structural transition. Charge ordering appears uniaxially along the short …
The newly discovered Kagome superconductors $A$V$_3$Sb$_5$ ($A$ = K, Rb, Cs) exhibit superconductivity, charge order, and band topology simultaneously. To explore the intricate interplay between the superconducting and charge orders, we investigate the doping evolution of superconductivity, charge-density-wave (CDW) order, and band topology in doped topological kagome superconductors Cs(V$_{1-x}$Ti$_x$)$_3$Sb$_5$ where the Ti-dopant introduces hole-like charge carriers. Despite the absence of the CDW phase transition in doped compounds even for the lowest doping level of $x=0.047$, the superco…
Orbital Separation of Charge Order and Superconductivity in La$_{2-x}$Sr$_{x}$CuO$_4$
Universität Zürich（苏黎世大学）；PSI Center for Neutron and Muon Sciences CNM（瑞士保罗谢勒研究所中子与μ子科学中心）；European Synchrotron Radiation Facility（欧洲同步辐射装置）；Diamond Light Source（钻石光源）；Korea Advanced Institute of Science & Technology (KAIST)（韩国科学技术院）；Helmholtz-Zentrum Berlin für Materialien und Energie（柏林亥姆霍兹材料与能源中心）；Hokkaido University（北海道大学）；Muroran Institute of Technology（室兰工业技术学院）
