  Electron-lattice coupling effects in low dimensional materials give rise to
charge density wave (CDW) order and phase transitions. These phenomena are
critical ingredients for superconductivity and predominantly occur in metallic
model systems such as doped cuprates, transition metal dichalcogenides, and
more recently, in Kagome lattice materials. However, CDW in semiconducting
systems, specifically at the limit of low carrier concentration region, is
uncommon. Here, we combine electrical transport, synchrotron X-ray diffraction
and optical spectroscopy to discover CDW order in a quasi-one-dimensional (1D),
dilute d-band semiconductor, BaTiS3, which suggests the existence of strong
electron-phonon coupling. The CDW state further undergoes an unusual transition
featuring a sharp increase in carrier mobility. Our work establishes BaTiS3 as
a unique platform to study the CDW physics in the dilute filling limit to
explore novel electronic phases.
