Correlation between electronic and structural orders in 1 T -Ti Se2

The correlation between electronic and crystal structures of 1 T -Ti Se₂ in the charge-density wave (CDW) state is studied by x-ray diffraction in order to clarify basic properties in the CDW state, transport properties, and chirality. Three families of reflections are used to probe atomic displacements and the orbital asymmetry in Se. Two distinct onset temperatures are found: T_CDW and a lower T^* indicative for an onset of Se out-of-plane atomic displacements. T^* coincides with a DC resistivity maximum and the onset of the proposed gyrotropic (chiral) electronic structure. However, no indication for chirality is found. The relation between the atomic displacements and the transport properties is discussed in terms of Ti 3 d and Se 4 p states that only weakly couple to the CDW order.