A time-reversal symmetric topological magnetoelectric effect in 3D topological insulators

One of the hallmarks of time-reversal symmetric topological insulators in 3D is the topological magnetoelectric effect (TME). So far, a time-reversal breaking variant of this effect has attracted much attention, in the sense that the induced electric charge changes sign when the direction of an externally applied magnetic field is reversed. Theoretically, this effect is described by the so-called axion term. Here, we discuss a time-reversal symmetric TME, where the electric charge depends only on the magnitude of the magnetic field but is independent of its sign. We obtain this non-perturbative result both analytically and numerically, and suggest a mesoscopic setup to demonstrate it experimentally.