Gate-tunable resistance drops related to local superconducting gaps in thin TaS layers on SrTiO substrates

SrTiO基板上の薄いTaS層における局所超伝導ギャップに関連したゲート調整可能な抵抗低下

小杉 美央子*; 齊藤 英治; 吉川 貴史*; 他11名*

Kosugi, Mioko*; Saito, Eiji; Kikkawa, Takashi*; 11 of others*

Strontium titanate [SrTiO (STO)], a perovskite oxide with an extremely high gate-tunable dielectric constant () due to quantum paraelectric phases, is attracting considerable attention for yielding various physical phenomena when two-dimensional (2D) layers are integrated. Superconductivity is such a typical phenomenon. However, the influence of the STO substrates on enhancing transition temperatures () for (atomically) thin 2D flakes attached to them has been rarely investigated. Here, we report gate-tunable and gradual four-terminal resistance drops with critical onset () and scanning tunneling spectroscopy (STS) spectra in devices comprising thin TaS flakes attached on monolayer hexagonal boron nitride (hBN) spacer/STO substrates. Observation of STS spectra confirms the presence of local superconducting gaps. (similar to 1.5 meV) with transition ( three-times higher than previous reports of under absent pressure and strong position dependence of . Depending on on back gate voltages () and magnetic fields, there is a strong correlation between and the onset of superconductivity, implying an enhancement of approximately five times compared with the previous highest-onset values without pressure as the applied increases. The high onset and. are discussed based on screening of the long-range Coulomb interaction (CI) due to the high- of SrTiO, while the short-ranged CI remains strong in the 2D limit, causing the superconductivity. Using a monolayer hBN/SrTiO substrate with opens doors to enhancement in thin superconducting layers integrated on it and wide application due to the solid-state high- substrates.