We discovered the chirality of charge density waves (CDW) in 1T-TiSe2 by using scanning tunnelling microscopy (STM) and optical ellipsometry. We found that the CDW intensity becomes Ia1 : Ia2 : Ia3 = 1 : 0.7 ± 0.1 : 0.5 ± 0.1, where Iai (i =1, 2, 3) is the amplitude of the tunnelling current contributed by the CDWs. There were two states, in which the three intensity peaks of the CDW decrease c...
