Relativistic suppression of Auger recombination in Weyl semimetals

Abstract

Auger recombination (AR) being electron-hole annihilation with energy-momentum transfer to another carrier is believed to speed up in materials with small band gap. We theoretically show that this rule is violated in gapless three-dimensional materials with ultra-relativistic electron-hole dispersion, Weyl semimetals (WSM). Namely, AR is prohibited by energy-momentum conservation laws in prototypical WSM with a single Weyl node, even in the presence of anisotropy and tilt. In real multi-node WSM, the geometric dissimilarity of nodal dispersions enables weak inter-node AR, which is further suppressed by strong screening due to large number of nodes. While partial AR rates between the nodes of the same node group are mutually equal, the inter-group processes are non-reciprocal, so that one of groups is geometrically protected from AR. This geometrical protection prolongs AR lifetime up to two orders of magnitude, to the level of nanoseconds.

Dynamically Induced Excitonic Instability in Pumped Dirac Materials

“…The lifetime is of the order of 100 fs in graphene, however, we should note that there are other trARPES reports that do not show any population inversion in graphene within the temporal resolution of the experiment . In 3D TIs, the lifetime is extended to at least several ps in recent reports Suppression of Auger scattering that was theoretically predicted to occur in WSMs, could lead to population inversion with similar lifetimes …”

“…A recent theoretical work suggested that population inversion could be also realized in 3D DMs . It was shown that ultrarelativistic electronic dispersion of WSMs leads to strong suppression of Auger recombination due to phase space restrictions imposed by energy and momentum conservation.…”

“…[49] In 3D TIs, the lifetime is extended to at least several ps in recent reports [63] Suppression of Auger scattering that was theoretically predicted to occur in WSMs, could lead to population inversion with similar lifetimes. [111]…”

“…A recent theoretical work suggested that population inversion could be also realized in 3D DMs. [111] It was shown that ultrarelativistic electronic dispersion of WSMs leads to strong suppression of Auger recombination due to phase space restrictions imposed by energy and momentum conservation. Considering that the overall dynamics in 3D DMs is qualitatively similar to that of graphene, [59,60,62] suppressed Auger recombination can result in a population inversion on the timescales that are several orders of magnitude larger than in graphene and are comparable or larger than in 3D TIs.…”

Подавление Оже-Рекомбинации В Полуметаллах Вейля / Афанасьев А.Н., Грешнов А.А., Свинцов Д.А

“…Естественно, что наиболее остро проблема ОР встает в случае отсутствия энергетической щели как таковой. Однако, в недавно открытых материалах с ультрарелятивистским законом дисперсии носителейполуметаллах Вейля (ПМВ) [1] -ОР может быть сильно (на несколько порядков) подавлена [2]. В случае строго изотропного закона дисперсии или наличия единственной точки Вейля во всей зоне Бриллюэна процесс ОР оказывается запрещенным законами сохранения, а его интенсивность в пределе малого дополнительного рассеяния стремится к нулю (в отличие от графена [3]).…”