Hall conductivity in unconventional charge-density-wave systems

Charge density waves with unconventional order parameters, for instance, with d-wave symmetry (DDW), may be relevant in the underdoped regime of high-T-c cuprates or other quasione- or two-dimensional metals. A DDW state is characterized by two branches of low-lying electronic excitations. The resulting quantum mechanical current has an interbranch component which leads to an additional mass term in the expression for the Hall conductivity. This extra mass term is parametrically enhanced near the "hot spots" of fermionic dispersion and is non-neglegible as is shown by numerical calculations of the Hall number in the DDW state.