Termination of the spin-resolved integer quantum Hall effect

We report a magnetotransport study of the termination of the spin-resolved integer quantum Hall effect by controlled disorder in a gated GaAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As heterostructure. We have found that, for a given Nth Landau level, the difference in filling factors of a pair of spin-split resistivity peaks \ensuremath{\delta}${\ensuremath{\nu}}_{\mathrm{N}}$=|${\ensuremath{\nu}}_{\mathrm{N}\mathrm{\ensuremath{\uparrow}}}$-${\ensuremath{\nu}}_{\mathrm{N}\mathrm{\ensuremath{\downarrow}}}$| changes rapidly from one to zero near a critical density ${\mathrm{n}}_{\mathrm{c}}$. Scaling analysis shows that \ensuremath{\delta}${\ensuremath{\nu}}_{\mathrm{N}}$ collapses onto a single curve independent of N when plotted against the parameter (n-${\mathrm{n}}_{\mathrm{c}}$)/${\mathrm{n}}_{\mathrm{c}}$ for five Landau levels. The effect of increasing the Zeeman energy is also examined by tilting the direction of magnetic field relative to the plane of the two-dimensional electron gas. Our experiment suggests the termination of the spin-resolved quantum Hall effect is a phase transition.