Negative differential resistance and characteristic nonlinear electromagnetic response of a Topological Insulator

TL;DR

This paper demonstrates that negative differential resistance can arise in Dirac ring systems like topological insulators due to a novel physical mechanism, enabling new applications in terahertz signal generation.

Contribution

It introduces a new physical mechanism for negative differential resistance in Dirac ring systems, distinct from the Gunn effect, with potential for engineering high-frequency devices.

Findings

Negative differential resistance observed in Dirac ring systems.

Mechanism remains robust at finite temperature and impurity levels.

Potential for terahertz frequency upconversion devices.

Abstract

Materials exhibiting negative differential resistance have important applications in technologies involving microwave generation, which range from motion sensing to radio astronomy. Despite their usefulness, there has been few physical mechanisms giving rise to materials with such properties, i.e. GaAs employed in the Gunn diode. In this work, we show that negative differential resistance also generically arise in Dirac ring systems, an example of which has been experimentally observed in the surface states of Topological Insulators. This novel realization of negative differential resistance is based on a completely different physical mechanism from that of the Gunn effect, relying on the characteristic non-monotonicity of the response curve that remains robust in the presence of nonzero temperature, chemical potential, mass gap and impurity scattering. As such, it opens up new possibilities for engineering applications, such as frequency upconversion devices which are highly sought for terahertz signal generation. Our results may be tested with thin films of Bi2Se3 Topological Insulators, and are expected to hold qualitatively even in the absence of a strictly linear Dirac dispersion, as will be the case in more generic samples of Bi2Se3 and other materials with topologically nontrivial Fermi sea regions.