New interaction effects in quantum point contacts at high magnetic fields

We use DC-bias spectroscopy to study the electronic structure of quantum wires at finite and zero in-plane magnetic field. Our data exhibits a new interaction effect which demonstrates that electron–electron interactions profoundly affect the electronic structure of the quantum wire at all magnetic fields, not just in the region of the 0.7 structure or its high-field version, the Analog. We show that as spin-down (lowest energy) subbands populate, they abruptly drop in energy by as much as View the MathML source0.5meV. These jumps in energy increase with magnetic field. This new phenomenon also provides an explanation for the surprising resilience of the 0.7 structure to high temperatures. In addition, we present intriguing new evidence that a fully spin-polarised state can be induced in a quantum wire at zero magnetic field simply by applying a large DC-bias.