多带笼目超导体CsV_(3)Sb_(5)衍生体系的可调磁通涡旋束缚态

Vortices and bound states offer an effective means of comprehending the electronic properties of superconductors.Recently,surface-dependent vortex core states have been observed in the newly discovered kagome superconductors CsV_(3)Sb_(5).Although the spatial distribution of the sharp zero energy conductance peak appears similar to Majorana bound states arising from the superconducting Dirac surface states,its origin remains elusive.In this study,we present observations of tunable vortex bound states(VBSs)in two chemically-doped kagome superconductors Cs(V_(1-x)Tr_(x))_(3)Sb_(5)(Tr=Ta or Ti),using low-temperature scanning tunneling microscopy/spectroscopy.The CsV_(3)Sb_(5)-derived kagome superconductors exhibit full-gap-pairing superconductivity accompanied by the absence of long-range charge orders,in contrast to pristine CsV_(3)Sb_(5).Zero-energy conductance maps demonstrate a field-driven continuous reorientation transition of the vortex lattice,suggesting multiband superconductivity.The Ta-doped CsV_(3)Sb_(5)displays the conventional cross-shaped spatial evolution of Caroli-de Gennes-Matricon bound states,while the Tidoped CsV_(3)Sb_(5)exhibits a sharp,non-split zero-bias conductance peak(ZBCP)that persists over a long distance across the vortex.The spatial evolution of the non-split ZBCP is robust against surface effects and external magnetic field but is related to the doping concentrations.Our study reveals the tunable VBSs in multiband chemically-doped CsV_(3)Sb_(5)system and offers fresh insights into previously reported Y-shaped ZBCP in a non-quantum-limit condition at the surface of kagome superconductor.

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

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.