Casimir forces exerted by epsilon-near-zero hyperbolic materials

Abstract

The Casimir force exerted on a gold dipolar nanoparticle by a finite-thickness slab of the natural hyperbolic material namely, the ortorhombic crystalline modification of boron nitride, is investigated. The main contribution to the force originates from the TM-polarized waves, for frequencies at which the parallel and perpendicular components of the dielectric tensor reach minimal values. These frequencies differ from those corresponding to the Lorentzian resonances for the permittivity components. We show that when the slab is made of an isotropic epsilon-near-zero absorbing material the force on the nanoparticle is larger than that induced by a hyperbolic material, for similar values of the characteristic parameters. This fact makes these materials optimal in the use of Casimir’s forces for nanotechnology applications.

One‐Dimensional Epsilon‐Near‐Zero Crystals

“…At wavelengths where the real part of the dielectric permittivity crosses zero, accompanied by a reasonably low imaginary part, the fascinating Epsilon-Near-Zero (ENZ) wave propagation regime occurs. [2][3][4] The vanishing permittivity enables a large variety of interesting optical properties such as nonlinear effects, [5][6][7][8] adiabatic frequency shifting, [9] ultrafast optical switching, [10,11] negative refraction, [12] intraband optical conductivity, [13] phase singularity engineering, [14] appearance of Casimir forces, [15] and metatronics. [16] The ENZ regime occurs naturally in some materials.…”

Understanding and Controlling Mode Hybridization in Multicavity Optical Resonators Using Quantum Theory and the Surface Forces Apparatus

“…Moreover, a MTM cavity can be described as a single homogeneous layer with an effective dielectric response such that the real part of the permittivity crosses zero at resonance, while the imaginary part becomes very small . Such “epsilon-near-zero” (ENZ) permittivity is associated with many intriguing phenomena, including nonlinearity enhancement, negative refraction, , ultrafast optical switching, adiabatic frequency shifting, intraband optical conductivity, phase singularity, and appearance of Casimir forces . Compared to natural ENZ materials such as Ag and indium–tin-oxide (ITO), waveguides and hyperbolic metamaterials, metal-dielectric cavity resonators provide a simple and flexible design of ENZ modes with low losses in the visible spectrum, which can be used to engineer strong light-matter coupling …”