Necklace-State-Mediated Anomalous Enhancement of Transport in Anderson-Localized non-Hermitian Hybrid Systems

Non-Hermiticity is known to manifest interesting modifications in the transport properties of complex systems. We report an intriguing regime of transport of hybrid quasiparticles in a non-Hermitian setting. We calculate the probability of transport, quantified by the Thouless conductance, of hybrid plasmons under varying degrees of disorder. With increasing disorder, we initially observe an expected decrease in average transmission, followed by an anomalous rise at localizing disorder. The behavior originates from the confluence of hybridization and non-Hermiticity, in which the former realizes the aggregation of eigenvalues migrating under disorder, while the latter enables energy transfer between the eigenmodes. We find that the enhanced transmission is mediated by quasiparticle hopping over various Anderson-localized states within the so-formed necklace states. We note that, in this scenario, all configurations exhibit the formation of necklace states and enhanced transport, unlike the conventionally known behavior of necklace states which only occurs in rare configurations.

Figure 1

(a) Dispersion of hybrid plasmon polariton bands, with the propagating lower band (blue line) and radiative upper band (red line) resulting from the anticrossing of plasmon dispersion (dotted line) and the cavity mode (dashed line). (b) Calculated density of states for a finite system, with the hybridization gap emphasized in the inset.

Figure 2

(a) Migration of a few nonradiative band edge modes with increasing disorder. (b) Configurationally averaged DOS close to $E_{\mathrm{hy}}$ for three disorder strengths. (c) DOS for an individual configuration for the same disorder strengths, emphasizing the emergent band at strong disorder.

Figure 3

Thouless conductance $⟨g⟩$ with disorder strength in the vicinity of $E_{\mathrm{hy}}$ for the hybrid plasmonic (red circles) and the dielectric (black squares) system. Dashed blue line indicates $⟨g⟩=1$, demarcating localization regime for the hybrid system (vertical blue lines).

Figure 4

Intensity profile at the band edge at three disorders. Inset: Effective width of the intensity distribution (log $Y$ axis) at the band edge as a function of disorder.

Figure 5

(a) Schematic of a hybrid-plasmonic coupled resonator waveguide. (b) Intensity distribution (black curve) at a frequency $\omega$ at strong disorder in a configuration comprises three ${\psi }_i$’s labeled I (blue), II (green), and III (red). The transmission occurs through hopping via localized states.

Figure 6

Distribution of the mean separation between the peaks at $\delta =0.95$ (red curve). Black curve: Poisson distribution. Inset: Representative $|\varphi {|}^2$, illustrating the separations.