Observation and Strain Control of Electronic Phase Transitions in a Quasi-1D Chalcogenide BaTiS₃

BaTiS₃ is a member of ternary transition metal chalcogenides with hexagonal symmetry¹. For many years this material has been considered a trivial small bandgap semiconductor with no electron or lattice instabilities due to the nominally unoccupied Ti 3d orbitals². Here, we report the first experimental observation of a series of electronic phase transitions in single crystals of BaTiS₃ from electrical transport measurements. Two different phase transitions are identified from abrupt hysteric jumps in electrical resistance at 150-190 K and 245-255 K, respectively, which are further supported by complementary characterizations including synchrotron X-ray diffraction, optical spectroscopies and DFT calculations. These transitions are sensitive to external strain fields. By controlling the thermal strain between the crystal and embedding medium, we can tune the transitions systematically. Different responses of the two transitions to extrinsic strain field further hint of their distinct origins.