Large absorption efficiency in ultralow loss, composite plasmonic nanoparticles

We analyze the scattering problem of two conjoined subwavelength hemi-cylinders with different dielectric properties. After obtaining a general closed-form solution for the quasi-static potential, we focus on the anomalous resonances arising when one of the two particles is plasmonic. We show that large absorption may be obtained over a moderately broad frequency range, even in the limit of negligible material losses, and we highlight the physical reasons behind this apparent paradox. This counterintuitive response is discussed for relevant applications in energy-harvesting, sensing and nonlinear optical devices.