Tunable natural terahertz and mid-infrared hyperbolic plasmons in carbon phosphide

Strain engineering of hyperbolic plasmons in monolayer carbon phosphide: a first-principles study

“…Indeed, the rotation of the hyperbolic IFCs in the visible range by changing the frequency of the incoming photon is observed under strains of −8%, and −9%. Recently, it is observed only for the hyperbolic SPPs of electrostatically doped monolayer β-CP in the mid-IR range 74 and gated multilayer black phosphorous (between 10 and 20 nm thick) in the THz band. 94 Under moderate tensile strain, the hyperbolic regions are blue-shifted; however, they are modified to a narrower energy window which is extended in the visible region as compared to the NIR range, see Fig.…”

“…It is well known that graphene presents isotropic plasmons at all frequencies 87 and phosphorene has no hyperbolic plasmons below ultraviolet (UV) frequencies. 85 In contrast to gra- phene and phosphorene as parent elemental materials of β-CP, in undeformed β-CP (when ε b = 0%) as reported in our previous work, 74 the hyperbolic regime is extended from nearinfrared (NIR) to the visible frequency range.…”

“…As presented in Table 1, the graphene and phosphorene (parent elemental materials of β-CP) have no hyperbolic windows, while β-CP reveals hyperbolic regimes with different frequency intervals with respect to the type of process. The electrostatically doped β-CP presents a hyperbolic window of 5-31 THz, 74 while strained β-CP supports an ultra-wide hyperbolic window of 9-693 THz. As a result, strain engineering can dramatically extend the hyperbolic window of β-CP.…”

“…46 Consequently, a topological transition between elliptic and hyperbolic regimes is achieved at 99 terahertz (THz). 46 In our previous study 74 natural hyperbolic plasmons below ultraviolet frequencies in electrostatically doped β-CP were analyzed. The results showed that in a range of frequencies in the THz and mid-infrared (mid-IR), β-CP exhibits a natural hyperbolic window without the need to artificial patterning of the material surface.…”

Two-dimensional natural hyperbolic materials: from polaritons modulation to applications

“…In addition to 2D BP, WTe 2 and ZrSiSe, some the other layered anisotropic crystals, e.g., β-allotrope of carbon phosphide 89 and massive tilted 2D Dirac materials, 54,90 have been also theoretically predicted to support hyperbolic plasmons. Nevertheless, the experimental detection of hyperbolic plasmon polaritons has not yet been realized in these materials due to the demand for strong coupling between intraband and interband transitions.…”