Cadmium arsenide (Cd3As2) thin
films feature
a two-dimensional topological
insulator (2D TI) phase for certain thicknesses, which theoretically
hosts a set of counterpropagating helical edge states that are characteristic
of a quantum spin Hall (QSH) insulator. In devices containing electrostatically
defined junctions and for magnetic fields below a critical value,
chiral edge modes of the quantum Hall effect can coexist with QSH-like
edge modes. In this work, we use a quantum point contact (QPC) device
to characterize edge modes in the 2D TI phase of Cd3As2and to understand how they can be controllably transmitted,
which is important for use in future quantum interference devices.
We investigate equilibration among both types of modes and find non-spin-selective
equilibration. We also demonstrate the effect of the magnetic field
on suppressing equilibration. We discuss the potential role of QSH-like
modes in a transmission pathway that precludes full pinch-off.