Plasmons in the van der Waals charge-density-wave material 2H-TaSe2

Abstract

Plasmons in two-dimensional (2D) materials beyond graphene have recently gained much attention. However, the experimental investigation is limited due to the lack of suitable materials. Here, we experimentally demonstrate localized plasmons in a correlated 2D charge-density-wave (CDW) material: 2H-TaSe2. The plasmon resonance can cover a broad spectral range from the terahertz (40 μm) to the telecom (1.55 μm) region, which is further tunable by changing thickness and dielectric environments. The plasmon dispersion flattens at large wave vectors, resulted from the universal screening effect of interband transitions. More interestingly, anomalous temperature dependence of plasmon resonances associated with CDW excitations is observed. In the CDW phase, the plasmon peak close to the CDW excitation frequency becomes wider and asymmetric, mimicking two coupled oscillators. Our study not only reveals the universal role of the intrinsic screening on 2D plasmons, but also opens an avenue for tunable plasmons in 2D correlated materials.

Atomically Thin TaSe2 Film as a High‐Performance Substrate for Surface‐Enhanced Raman Scattering

“…A previous study reported that the SPR of TaSe 2 mainly occurs in the terahertz and telecom range. [ 23 ]…”

“…A previous study reported that the SPR of TaSe 2 mainly occurs in the terahertz and telecom range. [23] The SERS mechanism can be described using a polarization tensor equation: α = A + B + C, in which A denotes the molecular resonance and B and C represent the SPR and molecule-metal charge-transfer resonance at the Fermi level, respectively. [56] The SPR effect is excluded in this paper.…”

“…Other methods, such as liquid exfoliation and mechanical exfoliation, are also inefficient for practical usage. [19,22] As a typical semimetallic 2D material, TaSe 2 exhibits a charge density wave (CDW), [23] superconductivity, [24] and tunable electronic structures. [25] Therefore, it may be a suitable candidate for SERS substrate and may offer good performance on Raman biosensors.…”

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

“…The plasmon dispersion is obtained from the dynamical dielectric function tensor i.e. ε(q, ω) which is written in terms of the optical conductivity tensor using the following relation for free-standing 2D materials 24,95,96 εðq i ; ωÞ ¼ 1 þ j2πq i σ ii ðωÞ=ω; i ¼ x; y:…”

Quasi-stationary near-gate plasmons in van der Waals heterostructures

“…In 2D material (2DM) plasmonics, graphene/hBN and hBN/graphene/hBN are the most studied vdW heterostructures [23][24][25] because of high carrier mobilities [26] and easy control of the spectral range of interest (from mid-infrared to visible) by means of gate voltage. However, multitude of two-dimensional materials discovered for the past decade, open up new possibilities [27].…”