  In a one-dimensional (1D) system of interacting electrons, excitations of
spin and charge travel at different speeds, according to the theory of a
Tomonaga-Luttinger Liquid (TLL) at low energies. However, the clear observation
of this spin-charge separation is an ongoing challenge experimentally. We have
fabricated an electrostatically-gated 1D system in which we observe spin-charge
separation and also the predicted power-law suppression of tunnelling into the
1D system. The spin-charge separation persists even beyond the low-energy
regime where the TLL approximation should hold. TLL effects should therefore
also be important in similar, but shorter, electrostatically gated wires, where
interaction effects are being studied extensively worldwide.
