  Molecular electronics targets tiny devices exploiting the electronic
properties of the molecular orbitals, which can be tailored and controlled by
the chemical structure/conformation of the molecules. Many functional devices
have been experimentally demonstrated; however, these devices were operated in
the low frequency domain (mainly, dc to MHz). This represents a serious
limitation for electronic applications, albeit molecular devices working in the
THz regime were theoretically predicted. Here, we experimentally demonstrate
molecular THz switches at room temperature. The devices consist of
self-assembled monolayers of molecules bearing two conjugated moieties coupled
through a non-conjugated linker. These devices exhibit clear negative
differential conductance behaviors (peaks in the current-voltage curves), as
confirmed by ab initio simulations, which were reversibly suppressed under
illumination with a 30 THz wave. We analyze how the THz switching behavior
depends on the THz wave properties (power, frequency), and we benchmark that
these molecular devices would outperform actual THz detectors.
