化学掺杂笼目结构超导体CsV_(3-x)Ti_(x)Sb_(5)及其两个显著物相

Titanium doped kagome superconductor CsV_(3-x)Ti_(x)Sb_(5)and two distinct phases

钒基笼目结构(kagome)超导体CsV_(3)Sb_(5)展现出反常霍尔效应(AHE)、电荷密度波(CDW),相列序和配对密度波(PDW)等新奇物性而得到了广泛关注.在kagome层进行化学取代掺杂是直接揭示内禀物性相互关联机制的最有效途径之一,但目前尚未见报道.本文成功制备出钛(Ti)化学掺杂的CsV_(3)Sb_(5)单晶,其中Ti原子直接取代kagome层中的部分V原子.CsV_(3-x)Ti_(x)Sb_(5)展现出2个显著不同的物相:少取代相展示出一个非常规V形的超导能隙,同时与减弱的长程CDW、PDW、AHE和相列序共存;多取代相则为常规U形的超导能隙并与短程CDW共存,同时长程CDW、AHE、PDW和具有二重对称性的面内磁电阻均消失.除Ti元素外,作者还成功制备了Cr和Nb掺杂的CsV_(3)Sb_(5)单晶.该研究成果开辟了制备化学掺杂笼目超导体的新方法以及研究不同电子关联态和超导配对精确调控的新平台.

The vanadium-based kagome superconductor CsV_(3)Sb_(5) has attracted tremendous attention due to its unexcepted anomalous Hall effect(AHE),charge density waves(CDWs),nematicity,and a pseudogap pair density wave(PDW)coexisting with unconventional strong-coupling superconductivity.The origins of CDWs,unconventional superconductivity,and their correlation with different electronic states in this kagome system are of great significance,but so far,are still under debate.Chemical doping in the kagome layer provides one of the most direct ways to reveal the intrinsic physics,but remains unexplored.Here,we report,for the first time,the synthesis of Ti-substituted CsV_(3)Sb_(5) single crystals and its rich phase diagram mapping the evolution of intertwining electronic states.The Ti atoms directly substitute for V in the kagome layers.CsV_(3-x)Ti_(x)Sb_(5) shows two distinct superconductivity phases upon substitution.The Ti slightly-substituted phase displays an unconventional V-shaped superconductivity gap,coexisting with weakening CDW,PDW,AHE,and nematicity.The Ti highly-substituted phase has a U-shaped superconductivity gap concomitant with a short-range rotation symmetry breaking CDW,while long-range CDW,twofold symmetry of in-plane resistivity,AHE,and PDW are absent.Furthermore,we also demonstrate the chemical substitution of V atoms with other elements such as Cr and Nb,showing a different modulation on the superconductivity phases and CDWs.These findings open up a way to synthesise a new family of doped CsV_(3)Sb_(5) materials,and further represent a new platform for tuning the different correlated electronic states and superconducting pairing in kagome superconductors.