Fig. 5. Close-up of the spin energy mode.

a The odd-in-energy (i.e. $V_{\det }$) component of Fig. 4c, corresponding to a charge imbalance, which is well localised in both $V_{\det }$ and I_inj. As a function of $V_{\det }$, as expected, the charge imbalance only appears at the gap edge: the vertical dashed lines indicate $V_{\det }=\pm \mid \mathrm{\Delta }-{\mathrm{\Delta }}_{\det }-E_{\mathrm{Z}}\mid /e$. As a function of the injection current, the signal is maximal (horizontal dotted lines) when only spins of one species (spin down excitations) are injected: G_inj(V_inj) is shown as a thin black line; its scale in the horizontal direction is in arbitrary units. b A vertical slice of a at $V_{\det }=\left(\mathrm{\Delta }-{\mathrm{\Delta }}_{\det }-E_{\mathrm{Z}}\right)/e$ and the same measurement at different magnetic fields linearly spaced down to H = 0 T. The theoretical prediction for H = 1 T is shown in black. The charge imbalance increases slightly then decreases as the magnetic field is lowered. At H = 0 it is undetectable.