Fig. 4

Two pairs of TCO cells’ to construct two-bit memory. a Two-bit memory is composed of four TCO-based unit cells as shown in a schematic illustration (left) and photograph (right). The first two units from the left (i.e., left pair in blue color) form a first bit, and the other two unit cells (i.e., right pair in red color) form a second bit. The states of these two bits are determined by the rotational angles of the first and third unit cells, φ ₁ and φ ₃. b The potential energy of the system as a function of φ ₁ and φ ₃ is analyzed, where a darker region represents a lower level of the normalized potential energy (color map). We divide the φ ₁ and φ ₃ space into four regions: ‘00’, ‘01’, ‘10’, and ‘11’. Inset illustrations indicate a representative shape of the TCO cells for each region