When the Hall effect disappears in a large magnetic field

March 15, 2019

In a usual electric conductor, running an electric current perpendicular to a magnetic field produces a transverse electric field -- this is the Hall effect.  In a recent study, however, Phuan Ong's group at Princeton explored a material (KHgSb) for which the Hall effect goes away completely when the magnetic field is sufficiently strong.  On the other hand, the longitudinal conductivity remains finite.

Ong's group and I were able to explain this strange finding based on two ideas:

  1. The crystal structure of the material has a "non-symmorphic" symmetry that gives rise to "double quantum spin Hall" states which carry transverse current in equal and opposite directions on the material's surface. 
  2. The magnetic field causes the bulk electrons to localize onto impurity states, a phenomenon sometimes called "magnetic freezeout".