We have developed a two subband quantum Hall system that can be used to manipulate integer and fractional quantum Hall edge modes in ways which were unachievable before.
We have developed a two subband quantum Hall system that can be used to manipulate integer and fractional quantum Hall edge modes in ways which were unachievable before. Using this system we demonstrated the formation of robust helical modes and, for the first time to the best of our knowledge, fractional helical modes. These modes are highly desirable for creating Majorana zero modes and parafermionic zero modes that are the basic building blocks for topological quantum computations. While most platforms used by now in an attempt to realize these quasiparticles suffer from difficulties in robustness, fabrication methods and scalability, our platform, which is implemented in GaAs/AlGaAs heterostructures, provide evident advantages in these respects. Moreover for parafermionic zero modes it is almost essential to use the edge modes of the fractional quantum Hall effect which are most easily obtained in such heterostructures. Byond helical modes, we have used the new system to create compounded integer-fractional edge modes and probed the Kane-Fisher-Polchinski phase transition. We discovered interesting bias dependence which points to a strong suppression of tunneling at zero bias as well as an unexpected energy scale in the system, results which we are interpreting these days. We have demonstrated control over edge mode coupling, distance and spin and have started working towards a realization of an extremely small size Mach-Zehnder interferometer with no ohmic contact in its center.