  We theoretically investigate the tunneling spectroscopy of a system of two
parallel one-dimensional helical conductors in the interacting, Luttinger
liquid regime. We calculate the non-linear differential conductance as a
function of the voltage bias between the conductors and the orbital momentum
shift induced on tunneling electrons by an orthogonal magnetic field. We show
that the conductance map exhibits an interference pattern which is
characteristic to the interacting helical liquid. This can be contrasted with
the different interference pattern from tunneling between regular Luttinger
liquids which is governed by the spin-charge separation of the elementary
collective excitations.
