Valley-polarized quantum Hall phase in a strain-controlled Dirac system

In a semiconductor system, the different pockets where the electrons lie can be seen as a pseudospin “up” or “down”, which leads to novel physics phenomena and a new way to encode the information. Using mechanical strain to control the electron populations of these pockets, the authors of an article in Physical Review Letters, with members of the Nano-THz team of the LPENS, show that the pseudospin value can be varied, yielding distinct electronic transport signatures. Under an external magnetic field, non-dissipative charge carriers are evidenced to carry pseudospin “up”, “down” and even both coexisting together, depending on the strain status. In the latter case, surprisingly, the charge carriers are found to remain dissipationless (the current is flowing with no resistance), although they are spatially overlaid and counter-propagating. This observation raises questions about interactions between currents flowing with different pseudospins.