Low-dimensional ferroelectric tunnel junctions are appealing for the
realization of nanoscale nonvolatile memory devices due to their inherent
advantage of device miniaturization. Those based on current mechanisms still
have restrictions including low tunneling electroresistance (TER) effects and
complex heterostructures. Here, we introduce an entirely new TER mechanism to
construct the nanotube ferroelectric tunnel junction with ferroelectric
nanotubes as the tunneling region. When rolling a ferroelectric monolayer into
a nanotube, due to the coexistence of its intrinsic ferroelectric polarization
with the flexoelectric polarization induced by bending, there occurs
metal-insulator transition depending on radiative polarization states. For the
pristine monolayer, its out-of-plane polarization is tunable by an in-plane
electric field, the conducting states of the ferroelectric nanotube can thus be
tuned between metallic and insulating via axial electric means. Using
{\alpha}-In2Se3 as an example, our first-principles density functional theory
calculations and nonequilibrium Green's function formalism confirm the
feasibility of the TER mechanism and indicate an ultrahigh TER ratio exceeding
9.9*10^10% of the proposed nanotube ferroelectric tunnel junctions. Our
findings provide a promising approach based on simple homogeneous structures
for high density ferroelectric microelectronic devices with excellent ON/OFF
performance.Comment: 15 pages, 5 figure