  Using series expansion by continuous unitary transformations we study the
magnetic properties of a frustrated tetrahedral spin-1/2 chain. Starting from
the limit of isolated tetrahedra we analyze the evolution of the ground state
energy and the elementary triplet dispersion as a function of the
inter-tetrahedral coupling. The quantum phase diagram is evaluated and is shown
to incorporate a singlet product, a dimer, and a Haldane phase. Comparison of
our results with those from several other techniques, such as density matrix
renormalization group, exact diagonalization and bond-operator theory are
provided and convincing agreement is found.
