APS -APS March Meeting 2017 - Event - Bi-2212/TaS$_2$ Van der Waals Junctions: Interplay of proximity induced high-$T_c$ Superconductivity and CDW order

摘要

We present an experimental observation of high-$T_c$ superconducting proximity effect by using four-terminal current-voltage measurements to study the Van der Waals interface between freshly exfoliated flakes of the high-$T_{c}$ superconductor, Bi-2212, and the CDW-dominated TMD layered material, 1T-TaS$_{2}$. For highly transparent barriers, there is a pronounced Andreev reflection feature providing evidence for proximity-induced high-$T_{c}$ superconductivity in 1T-TaS$_{2}$ with a surprisingly large energy gap ($sim 20$meV) equal to half that of intrinsic Bi-2212 ($sim 40$meV). Our systematic study using conductance spectroscopy $dI/dV$ of junctions with different transparencies also reveals the presence of two separate boson modes, each associated with a ``dip-hump" structure. We infer that the proximity-induced high-$T_c$ superconductivity in the TaS$_2$ is driven by coupling to the metastable metallic phase coexisting within the Mott-CCDW (commensurate CDW) phase.