236 research outputs found
Density Wave States of Non-Zero Angular Momentum
We study the properties of states in which particle-hole pairs of non-zero
angular momentum condense. These states generalize charge- and
spin-density-wave states, in which s-wave particle-hole pairs condense. We show
that the p-wave spin-singlet state of this type has Peierls ordering, while the
d-wave spin-singlet state is the staggered flux state. We discuss model
Hamiltonians which favor p-wave and d-wave density wave order. There are
analogous orderings for pure spin models, which generalize spin-Peierls order.
The spin-triplet density wave states are accompanied by spin-1 Goldstone
bosons, but these excitations do not contribute to the spin-spin correlation
function. Hence, they must be detected with NQR or Raman scattering
experiments. Depending on the geometry and topology of the Fermi surface, these
states may admit gapless fermionic excitations. As the Fermi surface geometry
is changed, these excitations disappear at a transition which is third-order in
mean-field theory. The singlet d-wave and triplet p-wave density wave states
are separated from the corresponding superconducting states by zero-temperature
O(4)-symmetric critical point
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