The derivatives of the tunnelling conductance G, with respect to either B or Vdc, are plotted as a function of the dc-bias Vdc and in-plane magnetic field B perpendicular to the wires, for the regime of three 1D wire subbands filled, achieved by setting the wire–gate voltage to Vwg=−0.55 V. The electron density in the wires is n1D≅49 μm−1. The resonances marked by the solid and dashed green lines reveal the dispersion of the elementary excitations in the 2D lower well, in the W (wire) and L (lead) regions of the device, respectively. The resonances marked by the dash-dotted green lines reveal the dispersion in the 2D upper-well leads. The resonances marked by the black lines reveal (first subband) dispersions for elementary excitations in the 1D upper-well wires, for spinons (dashed lines) and for holons (solid lines). (a,b) Wide dG/dB and dG/dVdc maps. (c,d) High-resolution dG/dB and dG/dVdc maps, zooming in on the magnetic-field region , corresponding to the main wavenumber region for the 1D upper-well wires.