Bose-Einstein condensate of Dirac magnons: Pumping and collective modes

TL;DR

This paper investigates the formation, coherence, and collective excitations of a Bose-Einstein condensate of Dirac magnons in two-dimensional systems, highlighting the role of the Haldane gap in tuning collective modes.

Contribution

It introduces a multicomponent model for Dirac magnon BEC, analyzing its dynamics, coherence, and the influence of the Haldane gap on collective excitations.

Findings

Dirac magnon BEC exhibits Rabi oscillations related to spectrum gaps.

The Haldane gap controls the transition between gapped and gapless modes.

Collective mode spectrum can be used to probe Dirac nature of the condensate.

Abstract

We explore the formation and collective modes of Bose-Einstein condensate of Dirac magnons (Dirac BEC). While we focus on two-dimensional Dirac magnons, an employed approach is general and could be used to describe Bose-Einstein condensates with linear quasiparticle spectrum in various systems. By using a phenomenological multicomponent model of pumped boson population together with bosons residing at Dirac nodes, the formation and time evolution of condensates of Dirac bosons is investigated. The condensate coherence and its multicomponent nature are manifested in the Rabi oscillations whose period is determined by the gap in the spin-wave spectrum. A Dirac nature of the condensates could be also probed by the spectrum of collective modes. It is shown that the Haldane gap provides an efficient means to tune between the gapped and gapless collective modes as well as controls their stability.