  One-dimensional (1D) quantum systems, which are predicted to exhibit novel
states of matter in theory, have been elusive in experiment. Here we report a
superlattice method of creating artificial 1D quantum stripes, which offers
dimensional tunability from two- to one-dimensions. As a model system, we have
fabricated 1D iridium (Ir) stripes using a-axis oriented superlattices of a
relativistic Mott insulator Sr2IrO4 and a wide bandgap insulator LaSrGaO4, both
of which are crystals with layered structure. In addition to the successful
formation of 1D Ir-stripe structure, we have observed 1D quantum-confined
electronic states from optical spectroscopy and resonant inelastic x-ray
scattering. Since this 1D superlattice approach can be applied to a wide range
of layered materials, it opens a new era of 1D science.
