Two-dimensional superconductivity in a thick exfoliated kagome film

Abstract

We report the observation of two-dimensional superconductivity (2D SC) in exfoliated kagome metal CsV${}_3$Sb${}_5$ with a thickness far thicker than the atomic limit. By examining the critical current and upper critical magnetic fields ($H_{c2}$) of 40-60 nm thick films in the superconducting state, we identify a pronounced Berezinskii-Kosterlitz-Thouless (BKT) transition behavior, i.e. a drastic decrease of the superfluid stiffness near the transition, and a cusp-like feature of the angular dependent $H_{c2}$, both of which serve as direct evidence of 2D SC. In addition, an exceeding of the Pauli paramagnetic limit of the in-plane $H_{c2}$ is consistent with the 2D SC nature. The observed 2D SC occurs in thick films with the highest superconducting transition temperature $T_c$ and the lowest charge density wave transition temperature $T_{\mathrm{CDW}}$, which suggests that the charge density wave states are interrelated with the superconducting states. Our findings impose constraints in understanding the enhancement of SC in kagome superconductors, and illuminate pathways for achieving novel 2D superconducting states in more stable and much thicker systems.

6 pages and 4 figures for the main text; 10 pages and 9 figures for the Supplementary Materials

References in corpus (17)

• CsV${}_3$Sb${}_5$: a ${\mathbb{Z}}_2$ topological kagome metal with a superconducting ground state
• Roton pair density wave and unconventional strong-coupling superconductivity in a topological kagome metal
• Highly crystalline 2D superconductors
• High-temperature interface superconductivity between metallic and insulating cuprates
• Two-Dimensional Superconducting Fluctuations in Stripe-Ordered La(1.875)Ba(0.125)CuO(4)
• Twofold symmetry of $c$-axis resistivity in topological kagome superconductor CsV${}_3$Sb${}_5$ with in-plane rotating magnetic field
• AV${}_3$Sb${}_5$ Kagome Superconductors: Progress and Future Directions
• Nodeless superconductivity in the kagome metal CsV${}_3$Sb${}_5$
• Anisotropic superconducting properties of Kagome metal CsV3Sb5
• Fermi level tuning and double-dome superconductivity in the kagome metals CsV${}_3$Sb${}_{5-x}$Sn${}_x$
• Universal self-field critical current for thin-film superconductors
• Competition of superconductivity and charge density wave in selective oxidized CsV3Sb5 thin flakes
• Microscopic evidence for anisotropic multigap superconductivity in the CsV${}_3$Sb${}_5$ kagome superconductor
• Bulk evidence of anisotropic $s$-wave pairing with no sign change in the kagome superconductor CsV${}_3$Sb${}_5$
• Competing superconductivity and charge-density wave in Kagome metal CsV3Sb5: evidence from their evolutions with sample thickness
• Nodeless superconductivity in kagome metal CsV${}_3$Sb${}_5$ with and without time reversal symmetry breaking
• Violation of Emergent Rotational Symmetry in the Hexagonal Kagome Superconductor CsV3Sb5