Large-amplitude oscillation dynamics and domain suppression in a superlattice Bloch oscillator

TL;DR

This paper investigates the nonlinear current dynamics of a superlattice Bloch oscillator under combined dc and ac fields, revealing large-amplitude oscillations and a potential method to suppress domain instabilities.

Contribution

It introduces an analysis of how strong ac fields modify the differential conductivity and can suppress space charge instabilities in superlattice Bloch oscillators.

Findings

Identification of a dc bias range with positive dc differential conductivity

Demonstration of large-amplitude oscillations under combined fields

Proposal for suppressing domain instabilities

Abstract

We analyze the current dynamics of a superlattice Bloch oscillator under conditions where, in addition to the dc bias field causing a negative differential ac conductivity, a similarly strong ac field is present, at a frequency somewhat below the Bloch frequency associated with the dc field. The differential conductivity at the ac drive frequency is then negative, but, because of the strong non-linearities of the system, the dc differential conductivity is modified by the ac field. For a sufficiently strong ac field, there will be a dc bias range inside which the dc differential conductivity has turned positive, while the ac conductivity remains negative. The phenomenon should lend itself to the suppression of the domain-like space charge instabilities that are normally associated with a negative dc differential conductivity.