Formation of a protected sub-band for conduction in quantum point contacts under extreme biasing

Managing energy dissipation is critical to the scaling of current microelectronics(1-3) and to the development of novel deevices that use quantum coherence to achieve enhanced functionality(4). To this end, strategies are needed to tailor the electron-phonon interaction, which is the dominant mechanism for cooling non-equilibrium ('hot') carriers in experiments aimed at controlling the quantum state, this interaction causes decoherence that fundamentally disrupts device operation. Here, we show a contrasting behaviour, in which strong electron-photon scattering can instead be used to generate a robust mode for electrical conduction in GaAs quantum point contacts, driven into extreme non-equilibrium by nanosecond voltage pulses. When the amplitude of these pulses is much larger than all other relevant energy scales, strong electron-photon scattering induces an attraction between electrons in the quantum-point-contact channel, which leads to the spontaneous formation of a marrow current filament and to a renormalization of the electronic states responsible for transport. The lowest of these states coalesce to form a sub-band seperated from all others by an energy gap larger than the source voltage. Evidence for this renormalization is the transient conductance, which becomes planned near 2e(2)/h (e(x) electron charges h, planck constant) for a broad range of source and gate voltates. This collective non-equilibrium mode is observed over a wide range of temperature (4,2-300 k) and many provide an effective means to manage electron-phonon scattering in nanoscale devices.