Liquid crystal compound, liquid crystal composition and liquid crystal display device

A compound, represented by formula (1):

• wherein, in formula (1), Ra and Rb are independently hydrogen, fluorine, chlorine, —CN, —SF5, —C≡C—≡SF5 or alkyl having 1 to 20 carbons, and in Ra and Rb, at least one piece of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one piece of —CH2CH2— may be replaced by —CH═CH— or —C≡C—, and in the groups, at least one hydrogen may be replaced by fluorine or chlorine;
• A0, A1 and A2 are independently 1,4-cyclohexylene, 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, pyridazine-3,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl or naphthalene-2,6-diyl, and in A0, A1 and A2, at least one piece of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one piece of —CH2CH2— may be replaced by —CH═CH—, and in the groups, at least one hydrogen may be replaced by fluorine, chlorine, —CF3, —CHF2, —CH2F, —OCF3, —OCHF2 or —OCH2F;
• Z1 and Z2 are independently a single bond or alkylene having 1 to 4 carbons, and in Z1 and Z2, at least one piece of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one piece of —CH2CH2— may be replaced by —CH═CH—, and in the groups, at least one hydrogen may be replaced by fluorine or chlorine;
• one of Y1 and Y2 is fluorine, and the other is hydrogen;
• Rc is alkyl having 1 to 4 carbons, and in Rc, at least one piece of —CH2— may be replaced by —O—, —S—, —CO— or —SiH2—, and at least one piece of —CH2CH2— may be replaced by —CH═CH— or —C≡C—;
• and
• a and b are independently 0, 1, 2 or 3, and a sum of a and b is 0, 1, 2 or 3.