A quantum-well magnetic tunnel junction

Physics Magnetic tunnel junctions, which are essential to the function of hard drive read heads in modern computers, allow current to pass when the spins of their two ferromagnetic layers are pointing in the same direction. Eisenstein et al. built a magnetic tunnel junction out of much more exotic components: a bilayer of GaAs quantum wells, each hosting a two-dimensional electron gas. A perpendicular external magnetic field caused the electrons in each well to group into the so-called Landau energy levels. When the filling fraction was 5/2 in one layer and 7/2 in the other, the junction acted as a diode, allowing the tunneling of current in essentially only one direction. This suggests that each layer acted like a ferromagnet, with full spin polarization. Phys. Rev. Lett. 118 , 186801 (2017).