Two types of superconducting domes in unconventional superconductors

Abstract

Uncovering the origin of unconventional superconductivity is often plagued by the overwhelming material diversity with varying normal and superconducting (SC) properties. In this article, we deliver a comprehensive study of the SC properties and phase diagrams using multiple tunings (such as disorder, pressure or magnetic field in addition to doping and vice versa) across several families of unconventional superconductors, including the copper-oxides, heavy-fermions, organics and the recently discovered iron-pnictides, iron-chalcogenides, and oxybismuthides. We discover that all these families often possess two types of SC domes, with lower and higher SC transition temperatures T c , both unconventional but with distinct SC and normal states properties. The lower T c dome arises with or without a quantum critical point (QCP), and not always associated with a non-Fermi liquid (NFL) background. On the contrary, the higher-T c dome clearly stems from a NFL or strange metal phase, without an apparent intervening phase transition or a QCP. The two domes appear either fully separated in the phase diagram, or merged into one, or arise independently owing to their respective normal state characteristics. Our findings suggest that a QCP-related mechanism is an unlikely scenario for the NFL phase in these materials, and thereby narrows the possibility towards short-range fluctuations of various degrees of freedom in the momentum and frequency space. We also find that NFL physics may be a generic route to higher-T c superconductivity.As mentioned in section 3.2, the HF Ce-115 family can be tuned via multiple methods, including doping at every ionic site, pressure and magnetic field. Data obtained using various possible dopings is compiled in figure A1. In CeCo 1−x Rh x In 5, the doping versus T c plot does not exhibit an observable anomaly at the QCP, while an enhancement in T c would be expected here. On the other hand, CeRh 1−x Ir x In 5 exhibits a SC dome around a QCP [47]. However, in both cases the NFL state remains indifferent to the position of the QCP (∼50% doping), with the NFL state remaining dominant in the undoped case. As discussed in the main text, the application of pressure helps split the SC dome into two, and with increasing pressure the optimum T c in both domes increases [35].The In-site of Ce-115 has been doped with Cd ([49]) and Hg ([50]) giving rise to a magnetic phase. Similarly, doping with Sn ([184]) and Pt ([50]) also gives rise to a magnetic phase. In magnetic CeRh(In 1−x Cd x ) 5 , Cd doping first suppresses the AFM Nèel temperature (T N ) and with 7%-8% Cd doping T N shows a sudden upturn. No sign of superconductivity has been reported in this system. In CeCo(In 1−x Cd x ) 5 , superconductivity is suppressed while T N increases with doping and extrapolation of the T N curve points to the possible presence of a QCP around 2%-4% doping. On the other hand, in CeIr(In 1−x Cd x ) 5 superconductivity is suppressed rapidly and with 2%-3% doping AFM emerges. The phase diagram of CeIr(In 1−x Hg x ) 5 is...

Superconductivity in monocrystalline YNiSi3 and LuNiSi3

“…Assuming a spherical Fermi surface, the effective mass is m * = 1.51m 0 [the density of LuNiSi 3 is 6.5696(3) g/cm 3 ], the estimated mean free path is equal to l = 63 nm, lower than for YNiSi 3 , and the London penetration depth is 33(3) nm. Finally, the BCS coherence length in the clean limit is ξ 0 = 690(70) nm, and using the equations above for λ GL and ξ GL , we obtain κ = 0.42 (4). This value also puts LuNiSi 3 in the type-I limit but much closer to the borderline value of 0.707.…”

“…(5) and (6). expression C p (T )/T = γ N + βT 2 + BT 4 where the first term is due to the electronic contribution and the βT 2 + BT 4 terms describe the phonon contribution following the Debye model. The fit yields γ N = 4.04 (9)…”

“…The search for new superconductors (SCs) has, in the past decade, often focused on heavy-fermion materials and/or materials whose unit cells lack a center of inversion-the noncentrosymmetric (NCS) superconductors [1]. This is because these materials are thought to be good candidates for unconventional superconductors, which do not conform to the Bardeen-Cooper-Schrieffer (BCS) theory [2][3][4][5] and can exhibit high critical fields-on the order of a few teslas-as well as high critical temperatures. Despite the large number of reported studies, the relationship between a material's crystal structure and its superconducting properties is not yet firmly established.…”

Pressure-induced reemergence of superconductivity in the topological kagome metal CsV3Sb5

“…Origin of superconductivity--Reemergence of superconductivity has been reported in various materials that show unconventional superconductivity and have different interpretations [18]. Crystal structure phase transition is usually responsible to two-dome superconductivity, such as to Sr0.065Bi2Se3 [28] and LaFeAsO1-xFx (0≤x≤0.75) [29].…”

“…Interestingly, multiple SC domes (e.g. two domes), a strong precursor of unconventional superconductivity, was reported in various materials [18], such as A1-xFe2-ySe2 (A= K, Rb, Tl/K, or Tl/Rb) [19], (Li1-xFex)OHFe1-ySe [20], CeCu2(Si1-xGex-2) [21] and LaxBa2-xCu0.99M0.01O4 (M = Cu, Ni, Zn and Ga) [22,23]. Whether AV 3Sb5 could support the unconventional multiple-dome superconductivity under pressure is highly desired.…”