Spin-charge gauge approach to metal–insulator crossover and transport properties in high-Tc cuprates

The spin-charge gauge approach to the metal–insulator crossover (MIC) and other anomalous transport properties in high-Tc cuprates is briefly reviewed. A U(1) field gauging the global charge symmetry and an SU(2) field gauging the global spin–rotational symmetry are introduced to study the two-dimensional t–J model in the limit . The MIC, as a clue to the understanding of the ‘pseudogap’ (PG) phase, is attributed to the competition between the short-range antiferromagnetic order and dissipative motion of charge carriers coupled to the slave-particle gauge field. The composite particle formed by binding the charge carrier (holon) and spin excitation (spinon) via the slave-particle gauge field exhibits a number of peculiar properties, and the calculated results are in good agreement with experimental data for both PG and ‘strange metal’ phases. Connections to other gauge field approaches in studying the strong correlation problem are also briefly outlined.