  One-dimensional (1D) confinement has been revealed to effectively tune the
properties of materials in homogeneous states. The 1D physics can be further
enriched by electronic inhomogeneity, which unfortunately remains largely
unknown. Here we demonstrate the ultra-high sensitivity to magnetic
fluctuations and the tunability of phase stability in the electronic transport
properties of self-assembled electronically phase-separated manganite nanowires
with extreme aspect ratio. The onset of magnetic nano-droplet state, a
precursor to the ferromagnetic metallic state, is unambiguously revealed, which
is attributed to the small lateral size of the nanowires that is comparable to
the droplet size. Moreover, the quasi-1D anisotropy stabilizes thin insulating
domains to form intrinsic tunneling junctions in the low temperature range,
which is robust even under magnetic field up to 14 T, and thus essentially
modifies the classic 1D percolation picture to stabilize a novel quantum
percolation state. A new phase diagram is therefore established for the
manganite system under quasi-1D confinement for the first time. Our findings
offer new insight to understand and manipulate the colorful properties of the
electronically phase-separated systems via dimensionality engineering.
