Hyperbolic plasmon–phonon dispersion on group velocity reversal and tunable spontaneous emission in graphene–ferroelectric substrate

Abstract

This work presents a new substrate platform, which provides tunability of the group velocity and spontaneous emission of a dipolar scatterer graphene-ferroelectric slab hybrid system in the terahertz ranges. We use analytical models to determine the hybridization of graphene surface plasmon and ferroelectric LiNbO 3 type I and type II reststrahlen hyperbolic phonon-polariton. The variation of the chemical potential of graphene and the thickness of the ferroelectric layer results in several distinct features. Flipping the group velocity, strongly coupled hybrid hyperbolic surface plasmon-polaritons, and surface plasmon-polariton mode exists for the same momentum at different frequencies. The group velocity sign reversal for both a single-graphene-and doublegraphene-integrated system depends on the thickness of the hyperbolic layer and the chemical potential of graphene. Comparative analysis of Purcell radiation is presented for a quantum emitter positioned at different locations between ferroelectric and graphene-integrated ferroelectric layers, revealing that this system can support strong spontaneous emission that can be modulated with the graphene chemical potential. Changing the chemical potential through selective voltage biasing demonstrates a substantial increase or decrease in the decay rate for spontaneous emission. Further analysis of the emission phenomenon shows a dependence on factors, such as the relative radiating source position and the thickness of the ferroelectric film. These characteristics make graphene-ferroelectric materials promising candidates to modify the light-matter interaction at the low terahertz ranges.

Terahertz binding of nanoparticles based on graphene surface plasmons excitations

“…( 13) is imaginary, it is follows that ∂ ∂x Ĝs,xx (r ′ , r ′ ) is imaginary, consequently the last term in Eqs. ( 14) and (15) does not contribute to the force. Taking derivative respect to x variable, and considering p Ax = p Bx = p x (the field is normally incident on the surface), Eq.…”

“…Note that we have included the superscript x and y in Eqs. ( 14) and (15) to indicate the direction of the incident electric field. Since, Ĝs,xx (r ′ , r ′ ) given by Eq.…”

“…For example, GSPs have been proposed as a new generation of nano antennas for communications in the THz bands [11], molecular sensors capable to selectively enhance individual spectral features [12,13], low frequency spaser (see [14] and Refs. therein) and for enhancing the spontaneous emission and energy transfer between molecules [15,16,17]. Recently, the use of high-quality GSP resonances on twin graphene-coated dielectric rods to enhance the diffraction radiation intensity in the IR region has been demonstrated [18].…”

Gate tunable light-matter interaction in natural biaxial hyperbolic van der Waals heterostructures

“…On the contrary, hyperbolic PhPs are relatively less lossy but are restricted within a narrow spectral bandwidth [23]. To this end, the integration of graphene with h-BN [24][25][26] and other dielectric crystals [27,28] has shown gate-voltage tunable hybrid plasmon-phonon polaritons (HPPPs). The HPPP modes provide anisotropic propagation of polaritons [26] up to 2 times longer distances than hyperbolic PhPs [29] with reduced damping [24].…”

“…However, there exists a wide spectral * anshuman.kumar@iitb.ac.in gap (400 cm −1 to 1100 cm −1 ) and uniaxial anisotropic h-BN crystal exhibits narrow Reststrahlen Bands (RBs)spectral region between LO and TO phonons of a particular polarization. Furthermore, anisotropy of SERs for heterostructure of graphene with other hyperbolic materials like h-BN and LiNbO3 is further restricted by their uniaxial nature [25,27,28]. This challenge can be addressed via recently discovered natural vdW crystal [4], i.e.…”