  The research interest in the supercurrent diode effect (SDE) has been
growing. It has been found in various kinds of systems, in a large part of
which it may be understood by combining spin-orbit coupling and Zeeman field.
Here, we show that there exists another mechanism of generating SDE in chiral
nanotubes that trap magnetic fluxes, without spin-orbit coupling or Zeeman
field. We further show that the same generalized Ginzburg-Landau theory leads
to nonreciprocal paraconductivity (NPC) near the transition temperature. The
main features of both the SDE and the NPC are revealed by their parameter
dependence. Our study suggests a new kind of platforms to explore nonreciprocal
properties of superconducting materials. It also provides a theoretical link
between the SDE and the NPC, which were often studied separately.
