Magnetic plasmon resonances in nanostructured topological insulators for strongly enhanced light–mos2 interactions

ABSTRACT Magnetic resonances not only play crucial roles in artificial magnetic materials but also offer a promising way for light control and interaction with matter. Recently, magnetic

resonance effects have attracted special attention in plasmonic systems for overcoming magnetic response saturation at high frequencies and realizing high-performance optical

functionalities. As novel states of matter, topological insulators (TIs) present topologically protected conducting surfaces and insulating bulks in a broad optical range, providing new

building blocks for plasmonics. However, until now, high-frequency (e.g. visible range) magnetic resonances and related applications have not been demonstrated in TI systems. Herein, we

report for the first time, to our knowledge, a kind of visible range magnetic plasmon resonances (MPRs) in TI structures composed of nanofabricated Sb2Te3 nanogrooves. The experimental

results show that the MPR response can be tailored by adjusting the nanogroove height, width, and pitch, which agrees well with the simulations and theoretical calculations. Moreover, we

innovatively integrated monolayer MoS2 onto a TI nanostructure and observed strongly reinforced light–MoS2 interactions induced by a significant MPR-induced electric field enhancement,

remarkable compared with TI-based electric plasmon resonances (EPRs). The MoS2 photoluminescence can be flexibly tuned by controlling the incident light polarization. These results enrich TI

optical physics and applications in highly efficient optical functionalities as well as artificial magnetic materials at high frequencies. SIMILAR CONTENT BEING VIEWED BY OTHERS QUANTIFYING

PHOTOINDUCED CARRIERS TRANSPORT IN EXCITON–POLARITON COUPLING OF MOS2 MONOLAYERS Article Open access 23 April 2021 MOIRÉ-ENGINEERED LIGHT-MATTER INTERACTIONS IN MOS2/WSE2 HETEROBILAYERS AT

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Open access 11 March 2025 INTRODUCTION Artificially structured materials have been broadly used to excite strong magnetic responses for the generation of crucial counterintuitive phenomena,

including negative refraction, invisible cloaking, superlensing, etc.1,2. To overcome the weak magnetism of natural materials at optical frequencies, metallic molecules (e.g., split rings)

with magnetic resonances induced by conduction current loops were proposed to construct artificial magnetic materials with negative refractive indices in the terahertz (THz) and mid-infrared

ranges3,4. However, transferring magnetic resonances to higher frequencies (especially in the visible range) is restricted by the magnetic response saturation and stringent nanofabrication

requirements5,6. Fortunately, magnetic resonances with the generation of displacement current loops were observed in specially designed plasmonic nanostructures, such as metallic nanopillar

pairs6, tailored nanoclusters7, and particle-film systems8,9. These magnetic plasmon resonances (MPRs) possess excellent capabilities for engineering magnetism, confining light at the

nanoscale, and enhancing the optical field in the high-frequency range, thus contributing to promising applications in light manipulation, perfect absorption, sensitive sensing and

reinforced light-matter interactions6,7,8,9,10. To broaden the actual applications of MPRs, novel materials are currently highly desirable to open new doors for the generation and control of

magnetic resonance behavior at optical frequencies. For example, graphene split rings were theoretically predicted to produce a magnetic resonant response stronger than traditional metallic

structures, but their operating frequencies were limited to the far-infrared range11. Recently, topological insulators (TIs), as new quantum states of matter, have attracted wide attention

in electronics, optics, and plasmonics12,13,14,15,16,17,18,19,20,21. TIs present unconventional conducting edge (or surface) states with topological protection caused by strong spin–orbit

coupling of insulating bulk states, distinct from ordinary metals and insulators12,13. The time-reversal symmetry of edge (or surface) states with gapless Dirac fermions enables the

avoidance of carrier backscattering from non-magnetic impurities13,14. The topological edge state was first confirmed in mercury telluride two-dimensional (2D) quantum wells12. Afterward,

topological surface states with exotic Dirac cones were discovered in three-dimensional (3D) nanomaterials (e.g. Sb2Te3, Bi2Te3, and Bi2Se3)13,14. In 2019, thousands of materials were

predicted to possess TI properties, paving a prospective path for quantum computing, spintronics, and devices with lower energy consumption22,23. Recently, Bi2Te3, Bi2Se3, and

Bi1.5Sb0.5Te1.8Se1.2 TIs have been verified to display ultrahigh refractive indices and light-driven plasmonic activities in an ultrabroad optical range from ultraviolet (UV) to

THz16,17,18,19,20,21. MPRs in TIs will be particularly useful for promoting the high-frequency optical activities of TIs and enriching their practical applications, especially in

light-matter interactions. However, until now, MPRs and relevant applications have not been reported in TI systems. Herein, we demonstrate for the first time, to our knowledge, a kind of

visible range MPR effect in nanofabricated single-crystalline Sb2Te3 TI nanogrooves. The experimental results reveal that the MPR response has a particular dependence on the nanogroove

height, width, and pitch, consistent with simulations and theoretical calculations. To explore actual applications of TI MPRs, we innovatively integrated monolayer MoS2 with a nanostructured

TI to improve the intrinsically weak interactions between light and atomic-layer materials. Polarization-dependent photoluminescence (PL) emission was experimentally observed and reasonably

analyzed. Benefitting from the strong MPR-induced electric field enhancement, the MoS2 PL intensity was remarkably reinforced compared with TI electric plasmon resonances (EPRs). These

results will open a new door for exploring novel TI optical physics and applications in optoelectronic devices and artificial magnetic materials. RESULTS OPTICAL CONSTANT AND NANOSTRUCTURE

OF THE SB2TE3 SINGLE CRYSTAL As shown in Fig. 1a, the TI nanogroove grating structure is fabricated on the surface of a Sb2Te3 single-crystal film using the focused ion beam (FIB) milling

method (see “Materials and methods” section). The height, width, and pitch of the nanogrooves are denoted by _h_, _d_, and _p_, respectively. As a primary member of the 3D TI family, the

Sb2Te3 material possesses distinctly discrepant surface and bulk states, exhibiting excellent optical characteristics13,15. Here, the Sb2Te3 single crystal is grown using the melting and

slow-cooling method (see “Materials and methods” section). To clarify the material morphology, we employ transmission electron microscopy (TEM) to obtain the selected area electron

diffraction (SAED) pattern and a high-resolution TEM (HRTEM) image of the Sb2Te3 microflake. The Sb2Te3 microflake depicted in Fig. 1b is fabricated through mechanical exfoliation and

chemical etching methods (Supplementary Methods). As shown in Fig. 1c, the sharp diffraction spots and atomic lattice arrangement verify the hexagonal packed structure of the high-quality

Sb2Te3 single crystal. The chemical composition is confirmed by energy-dispersive X-ray spectroscopy (EDS), revealing that the elemental molar ratio of Sb:Te is 2:3 (Supplementary Fig. S1).

The high crystalline quality of Sb2Te3 can be further verified by the Raman spectrum (Supplementary Fig. S2). The complex relative permittivities of TI materials can be measured by a

spectroscopic ellipsometer with considering the surface and bulk states17. The conducting surface and insulating bulk can be fitted with the Drude and Tauc–Lorentz dispersion formulas,

respectively (Supplementary Methods). Figure 1d shows the fitted relative permittivity of single-crystalline Sb2Te3 in the UV, visible, and near-infrared ranges, which agrees well with the

experimental results. The surface and bulk permittivities (_ε_s and _ε_b) are depicted in Fig. 1e, f, respectively. The surface permittivity satisfies the conditions of Re(_ε_s) < 0 and

−Re(_ε_s) > Im(_ε_s) at wavelengths from 250 to 2065 nm. This metal-like property of the surface state provides the possibility of generating the plasmonic response at high

frequencies24,25,26. The negative permittivity of the bulk state at shorter wavelengths (from 253 to 760 nm) can be attributed to the strong interband electronic absorption similar to

semiconductors17. Thus, the bulk state can also contribute to the formation of plasmonic resonances at visible wavelengths of less than 760 nm. The surface and bulk states together give rise

to the negative permittivity of Sb2Te3 at wavelengths from 250 to 895 nm, as shown in Fig. 1d. The fitting results (Supplementary Table S1) illustrate that the Sb2Te3 bulk possesses a

bandgap of ~0.33 eV, which is consistent with the reported 0.3 eV27. The Sb2Te3 surface presents an ultrathin layer of 2.6 nm (i.e., _t_ = 2.6 nm), similar to the reported 2.5 nm for the TIs

in the same family28. To the best of our knowledge, this is the first report of surface and bulk optical constants for the Sb2Te3 single crystal, laying the foundation for exploring Sb2Te3

optical activities and functionalities. MAGNETIC PLASMON RESONANCES IN SB2TE3 NANOSTRUCTURES First, a nanogroove grating with _h_ = 110 nm, _d_ = 130 nm, and _p_ = 450 nm is fabricated on

the Sb2Te3 film (with a thickness of >300 nm) mechanically exfoliated onto a Si substrate. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to measure the

structural profile of the nanogrooves, as shown in Fig. 2a, b, respectively. The reflection spectra from the Sb2Te3 nanogroove grating are measured using a micro-spectrometer system (see

“Materials and methods” section). The experimental results in Fig. 2c reveal that the incident light with polarization perpendicular to the nanogrooves (i.e., _θ_ = 0°) possesses a distinct

reflection dip at ~736 nm. However, the reflection dip disappears when the polarization is parallel to the nanogrooves (i.e., _θ_ = 90°). The finite-difference time-domain (FDTD) numerical

simulations (see “Materials and methods” section) agree well with the experimental results, as depicted in Fig. 2d. To clarify the reflection mechanism, we plot the magnetic and electric

field distributions at the reflection dip when _θ_ = 0°, as shown in Fig. 2e, f, respectively. Interestingly, the magnetic field energies are enhanced and are mainly concentrated in the

Sb2Te3 nanogrooves, exhibiting a strong diamagnetic effect. In Fig. 2f, the arrows indicate the direction and amplitude of the electric field vector, revealing the generation of displacement

current loops in the nanogrooves. The electric current along the nanogroove surface is excited by the magnetic field component parallel to the Sb2Te3 nanogroove (Supplementary Fig. S3). The

visible range resonance generated in this split-ring-like TI nanostructure is regarded as a typical magnetic resonance similar to MPR29. When the magnetic field component of incident light

is perpendicular to the nanogrooves (i.e., _θ_ = 90°), the magnetic resonance cannot be effectively excited, restraining the appearance of the reflection dip. Under the resonant condition,

the TI surface charges accumulate at the upper corners of the nanogrooves, accompanied by a strong electric field intensity (|_E_/_E_i|2) enhancement of >200-fold, as depicted in Fig. 2f.

From Fig. 2c, we find that TIs can present a broader MPR (or MPR-like) spectrum than metals. The broad MPR spectrum contributes to a relatively large wavelength range for strong field

enhancement. The significant field enhancement in nanostructured TIs will open a new door for the improvement of nanoscale light-matter interactions. It is worth noting that the TI surface

layer contributes to the redshift and narrowing of the resonant spectrum17 (Supplementary Fig. S4a). At the MPR wavelength, the TI surface and bulk present absorption peak values of ~6% and

~94%, respectively (Supplementary Fig. S4b). Subsequently, we investigate the dependence of the magnetic resonance on the structural parameters (i.e., height _h_, width _d_, and pitch _p_)

of the Sb2Te3 TI nanogrooves. Figure 3a shows that the reflection dip presents a distinct redshift with increasing _h_ when _θ_ = 0°. The MPR wavelength has a nearly linear relationship with

_h_ when _p_ = 450 nm and _d_ = 130 nm, as depicted in Fig. 3b. The experimental results are in excellent agreement with the numerical simulations. The MPRs can be reasonably analyzed by a

mutual inductor–inductor–capacitor (MLC) circuit model30. The MPR wavelength can be described as _λ__M_ = 2_πc_[(_L_ + _M_)_C_]0.5, where _L_, _M_, and _C_ are the inductance containing the

nanogroove ridge inductance/kinetic inductance, the mutual inductance between two adjacent circuits, and the capacitance between two nanogroove ridges (Supplementary Methods). According to

the MLC circuit model, we can theoretically deduce the MPR wavelength in the Sb2Te3 nanogrooves. The theoretical calculations are well consistent with the experimental and simulation

results, as shown in Fig. 3b. The MLC circuit model indicates that the MPR response is also dependent on the nanogroove width _d_. Here, we measure the reflection spectra from the Sb2Te3

nanogroove gratings with different _d_ when _h_ = 110 nm and _p_ = 450 nm. The experimental results in Fig. 3c demonstrate that the MPR wavelength exhibits a blueshift as _d_ increases,

which agrees well with the simulations (Supplementary Fig. S5). We also find that the MPR response also depends on the pitch of the nanogroove grating. The experiments in Fig. 3d show that

the MPR wavelength redshifts with increasing _p_, in accordance with the simulations (Supplementary Fig. S5). From the MLC circuit model, we can see that the mutual inductance _M_ increases

with _p_, giving rise to the redshift of _λ__M_. The nanogroove height, width, and pitch are the effective parameters for the tuning and selection of MPR wavelengths in TIs. PL EMISSION FROM

THE MONOLAYER MOS2/SB2TE3 NANOGROOVE HETEROSTRUCTURE As mentioned above, the magnetic resonance in the TI nanostructure with strong field enhancement may offer a promising route for

boosting light-matter interactions. Transition metal dichalcogenides (TMDCs), as a kind of 2D materials with unique semiconductor-like band structures, are regarded as a favorable platform

for advancing next-generation optoelectronics due to the unique electric, mechanical and optical properties31,32. As a prototypical TMDC semiconductor, MoS2 possesses a state transition from

an indirect bandgap of 1.2 eV to a direct bandgap of 1.8 eV as it transforms from bulk to monolayer31,33. The photoemission, excitonic binding, and chemical stability of monolayer MoS2 have

drawn wide attention for the PL emission, promoting the achievement of atomically thin active light emitters and sources33,34,35. However, the atomically thin layer with poor light-matter

interactions hinders the substantial application of MoS2 for light harvesting and emission33,35. Here, we innovatively integrate a MoS2 atomic monolayer with a Sb2Te3 TI nanostructure to

explore the tailoring and enhancement of PL emission. As depicted in Figs. 1a and 4a, a MoS2 flake is mechanically exfoliated and coated on the Sb2Te3 nanogrooves using the fixed-point

transfer method (see “Materials and methods” section). Figure 4b, c shows SEM images of the Sb2Te3 nanostructure before and after transferring the MoS2 flake, respectively. We can see that

the MoS2 layer is precisely transferred onto the Sb2Te3 film with fabricated nanogrooves. The nanogroove grating is fabricated with _h_ = 50 nm, _d_ = 130 nm, and _p_ = 400 nm on the Sb2Te3

film with a thickness of ~200 nm, as shown in Fig. 4d, e. The Raman spectrum in Fig. 4f shows that the in-plane vibrational mode \(E^1_{2g}\) and out-of-plane vibrational mode A1_g_ can be

excited when a 532 nm laser beam impinges onto the MoS2 layer over Sb2Te3. The frequency difference between the \(E^1_{2g}\) and A1_g_ modes is ~18.5 cm−1, which agrees well with the

reported value of monolayer MoS234. As depicted in the inset of Fig. 5a, the Sb2Te3 nanogroove grating with monolayer MoS2 presents a reflection dip at ~532 nm when _θ_ = 0° while retaining

a high reflection when _θ_ = 90°. This illustrates that the magnetic resonance can be generated at ~532 nm in the monolayer MoS2/Sb2Te3 nanogroove heterostructure. The numerical simulations

are consistent with the experimental results (Supplementary Fig. S6). To reveal the light–MoS2 interaction enhancement, we demonstrate the luminescence emission response in the monolayer

MoS2/Sb2Te3 nanogroove heterostructure using a confocal micro-spectrometry system with an excitation wavelength of 532 nm. Figure 5a displays the PL intensity spectra of the heterostructure

for different incident polarization angles. Two PL peaks occur at 674.5 and 618.0 nm when _θ_ = 90°, as can be more clearly seen in Supplementary Fig. S7. The inset of Fig. 5b depicts the PL

intensity map spectrally integrated from 665 to 695 nm in the dashed square frame of Fig. 4a when _θ_ = 0°. We can see that the Sb2Te3 nanogrooves with MoS2 can effectively excite the PL

signal, while the Sb2Te3 nanogrooves cannot solely emit upon photoexcitation, as shown in Fig. 5c. The above two PL peaks correspond to the positions of the A and B direct excitonic

transitions for monolayer MoS2 at the K point of the Brillouin zone36. The two resonances derive from the energy splitting from spin–orbit coupling of the valence band in monolayer

MoS236,37,38. The MoS2 PL emission is sensitive to the substrate. The PL emission intensity of MoS2 on SiO2 will be stronger than that of MoS2 on the TI film. As shown in Fig. 5a, the

intensities of the PL peaks drastically increase with the decrease in _θ_ from 90° to 0°. The PL emission intensity with _θ_ = 0° is particularly enhanced compared with the case of _θ_ = 

90°. Actually, the PL emission improvement is mainly dependent on the electric field enhancement in luminescent materials21,31,37. To clarify the mechanism of PL reinforcement, we

numerically calculate the integrated electric field intensity in the Sb2Te3 nanogrooves. In contrast with the electric field with _θ_ = 90°, we find that the enhancement factor of the

integrated electric field intensity at 532 nm monotonically decreases as _θ_ increases from 0° to 90°. As shown in Fig. 5b, the enhancement factor of the electric field intensity is close to

the reinforced strength of the MoS2 PL excitonic peak. Therefore, the electric field enhancement plays a critical role in the PL reinforcement. In addition, the MoS2 PL emission is

influenced by the support structures. The low reflection at the exciton wavelength may weaken the detected PL emission (Supplementary Fig. S8). Moreover, the PL peak wavelengths exhibit a

linear redshift with decreasing _θ_, as depicted in Fig. 5d. The shifts satisfy the relations _λ_ = 679.108–0.064_θ_ and _λ_ = 636.518–0.223_θ_ for the two PL peaks. When _θ_ = 0°, the PL

peaks can approach the 680.5 and 638.0 nm wavelengths. Here, the redshift of the PL peak can be attributed to the generation of trions (a type of quasi-particle state) in monolayer MoS2

induced by the doping of MPR-excited hot electrons37,38. The A− trion, neutral A exciton, and B exciton in MoS2 can be extracted by fitting the PL spectrum using the multi-Lorentzian fitting

method38. The MoS2 A− trion, A exciton, and B exciton peaks approximately localize at 687.4, 673.2, and 618.0 nm (i.e., 1.80, 1.84, and 2.01 eV) in the heterostructure with _θ_ = 90°,

respectively (Supplementary Fig. S7). The A exciton dominates the MoS2 PL emission when _θ_ = 90° and decays with decreasing _θ_, while the A− trion increases gradually. This may stem from

the higher hot-electron doping in MoS2 induced by the stronger magnetic resonance in the nanogrooves with smaller _θ_38. This phenomenon confirms the exciton-trion competition in plasmon

systems37. The MPR-induced field enhancement and exciton-trion competition result in the different portions of the A exciton and A-trion/B exciton when _θ_ changes from 90° to 0°

(Supplementary Fig. S7). The appearance of hot electron-induced trions may also cause the reduction of the PL enhancement37. The energy shift of the A peak is 20 meV when _θ_ changes from

90° to 0°, identical to the binding energy of trions in monolayer MoS238. The dependence of the PL emission height and position on the incident polarization offers a controllable scheme for

tailoring light–MoS2 interactions in artificial nanostructures. As depicted in Fig. 5c, the PL emission of monolayer MoS2 based on MPR shows a strong reinforcement of 21-fold, a remarkable

value compared with that of EPRs on TI nanoplates21. It should be noted that the PL emission reinforcement mainly results from the enhancement of the integrated electric field intensity in

the laser impingement area. Therefore, the reinforcement of the PL intensity is lower than that of the electric field in Fig. 2f. As shown in Fig. 4f, the Raman signal can be improved by one

order of magnitude with the generation of magnetic resonance. DISCUSSION In this article, the topological optical features of a Sb2Te3 single crystal have been experimentally demonstrated.

The results show that the surface and bulk states of the Sb2Te3 TI exhibit obvious metal- and semiconductor-like characteristics in the range from UV to near-infrared, respectively, enabling

plasmonic excitation at high frequencies. Visible range MPR-like magnetic resonances were first observed in Sb2Te3 nanogrooves nanofabricated using the FIB milling method, breaking through

the research limitation of TI EPRs16,17,18,19,20,21. Both the experimental and simulation results indicate that this MPR response particularly depends on the structural parameters. More

specifically, the MPR wavelength redshifts with increasing nanogroove height and pitch, while it presents a blueshift with increasing nanogroove width. The MPR behavior can be effectively

analyzed by the MLC circuit theoretical model. To explore potential applications of this MPR effect, we have integrated an advanced 2D nanomaterial (i.e., monolayer MoS2) with TI

nanostructures to boost the light-matter interactions as an example. The experimental results show that the PL emission of monolayer MoS2 can be dramatically reinforced with MPR generation,

breaking the intrinsic limitation of the poor interaction between light and atomically thin materials. The peak intensities and wavelengths of the MoS2 PL can be tuned by adjusting the

polarization angle of the incident light, which can be attributed to the resonance-induced polarization-dependent electric field enhancement and generation of the A− trion. The MoS2 PL

emission can be reinforced by 21-fold based on the MPRs in TI nanostructures, remarkably compared with TI-based EPRs21. The conventional Au material can also effectively promote the PL

emission of MoS239. TIs can support plasmons at wavelengths from UV to THz16,17,18,19,20,21, making the generation of electric/magnetic resonances in an ultrabroad range possible. The

excited wavelengths for Au-based PL enhancement can be extended by TI-based plasmons. The resonant field enhancement in the TI nanogrooves may not be the highest value, but the resonance

spectral width with strong field enhancement is particularly broad. When the resonance wavelength is located around the MoS2 PL peak position, the electric field at 532 nm can still be

enhanced by >100 times, which results in obvious MoS2 PL reinforcement (Supplementary Fig. S9). We find that the field enhancement can be further promoted through structural modification

(Supplementary Fig. S10), enabling more applications of TIs in optical devices, such as nanoscale light sources, nonlinear frequency converters, and light-harvesting elements. This kind of

magnetic resonance can also be generated in other TIs, such as Bi2Te3 and Bi2Se3. The various structures, such as nanopillars6, nanoclusters7, nanoparticles on film8,9, and nanocups10, will

further enrich MPR effects in TI systems. These results not only enrich TI optical physics but also advance applications of TIs in optoelectronic devices and artificial magnetic materials.

MATERIALS AND METHODS GROWTH OF THE SB2TE3 SINGLE CRYSTAL The high-quality Sb2Te3 single crystal is grown using the melting and slow-cooling method. High-purity Sb and Te powders with an

atomic ratio of 2:3, as the starting materials, are sealed in a quartz tube. The crystals can be grown in a vertical furnace according to the following procedures: (1) The Sb and Te mixed

powders are heated to 900 °C and completely melt. (2) The temperature is reduced quickly to 650 °C at a rate of 60 °C/h and then slowly to 550 °C at a rate of 2 °C/h. (3) The mixture is

naturally cooled to room temperature. The Sb2Te3 single-crystalline character and stoichiometry can be confirmed by TEM, Raman, and EDS characterization. FABRICATION OF SB2TE3 NANOSTRUCTURES

AND TRANSFER OF MOS2 The Sb2Te3 film is mechanically exfoliated on a Si substrate using “Scotch” tape from the Sb2Te3 single crystal. The nanogroove grating is fabricated on the Sb2Te3 film

using a FIB milling system (FEI Helios G4 CX) with a 30 kV voltage and a 7.7 pA current. The beam current should be controlled at a relatively low level for robust FIB fabrication. The MoS2

flakes are fabricated by exfoliating them from the MoS2 bulk material, repeatedly peeling them off with tape, and sticking them on a polydimethylsiloxane (PDMS) film. If a MoS2 flake on the

PDMS has the most transparent area of several microns in size, then the MoS2 flake is transferred onto the Sb2Te3 nanogrooves using an optical microscope/micromanipulation system. Thus, the

dry fixed-point transfer of MoS2 is completed. CHARACTERIZATION OF MATERIALS AND NANOSTRUCTURES The electron diffraction pattern and high-resolution TEM image of the Sb2Te3 single crystal

are obtained by TEM equipment (FEI Talos F200X) with a voltage of 200 kV. Raman spectra of MoS2 and Sb2Te3, as well as PL emission spectra, are acquired using confocal micro-spectrometry

(WITec Alpha 300R) with a linearly polarized 532 nm laser and an adjustable beam size (minimum diameter: 400 nm). SEM images of Sb2Te3 nanostructures are acquired by SEM equipment integrated

with the FIB (FEI Helios G4 CX) using a 5 kV voltage and a 21 pA current. To avoid damaging the TI material, the beam current should not be too high (<43 pA) for SEM imaging. AFM images

and height profiles of Sb2Te3 nanostructures are obtained by a commercial AFM system (Bruker). The relative permittivity of the Sb2Te3 single crystal in the UV, visible and near-infrared

ranges is measured by a spectroscopic ellipsometer (HORIBA) with an angle of 70° for incident light. Reflection spectra from Sb2Te3 nanogrooves with/without MoS2 are measured by a home-made

micro-spectrometer with a white light source impinging on the sample through a microscope and then reflected onto a CCD camera with a spectrometer (Andor). NUMERICAL SIMULATIONS The

reflection spectra and field distributions of Sb2Te3 nanostructures are numerically simulated using the FDTD method20,40,41. The perfectly matched layer absorbing boundary condition and

periodic boundary condition are set at the top/bottom and left/right sides of the computational space, respectively. A non-uniform mesh is employed in the _x_ and _z_ axis directions of TI

nanostructures. The maximum mesh steps of the Sb2Te3 surface layers and monolayer MoS2 (0.615 nm) are set as 0.3 nm and 0.1 nm, respectively. The maximum mesh step of the Sb2Te3 bulk layer,

air, and Si substrate is set as 5 nm. The relative permittivities in Fig. 1e, f are set for the surface and bulk states of the Sb2Te3 TI, respectively. The complex relative permittivity of

the Si substrate is achieved from experimental data42. The relative permittivity of monolayer MoS2 measured by Li et al. is used in the simulations43. The reflection spectra are calculated

using _R_ = |_P_r/_P_i|, where _P_i and _P_r are the light powers incident on and reflected from the Sb2Te3 nanostructures, respectively. DATA AVAILABILITY The data sets generated and

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supported by the National Key R&D Program of China (2017YFA0303800), National Natural Science Foundation of China (11974283, 61705186, 11774290, 11634010, and 61605065), Natural Science

Basic Research Plan in Shaanxi Province of China (2020JM-130), Guangzhou Science and Technology Program (201804010322), and Guangdong Basic and Applied Basic Research Foundation

(2020A1515011510). We thank the Analytical & Testing Center of Northwestern Polytechnical University (NPU) for the FIB nanofabrication as well as AFM, SEM, and TEM measurements. We also

thank Dr. C. Liu at NPU and Prof. X. Li at Westlake University for help with the TEM measurement and FIB fabrication. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * MOE Key Laboratory of

Material Physics and Chemistry under Extraordinary Conditions, and Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern

Polytechnical University, 710129, Xi’an, China Hua Lu, Yangwu Li, Mingwen Zhang, Xuetao Gan, Dong Mao, Fajun Xiao, Ting Mei & Jianlin Zhao * Institute for Superconducting &

Electronic Materials and ARC Centre of Excellence in Future Low-Energy Electronics, University of Wollongong, North Wollongong, NSW, 2500, Australia Zengji Yue, Weiyao Zhao & Xiaolin

Wang * Center for Artificial-Intelligence Nanophotonics, School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, 200093, Shanghai, China

Yinan Zhang & Min Gu * Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, 510632, Guangzhou, China

Yinan Zhang * State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, 710072, Xi’an, China Wei Zeng Authors *

Hua Lu View author publications You can also search for this author inPubMed Google Scholar * Zengji Yue View author publications You can also search for this author inPubMed Google Scholar

* Yangwu Li View author publications You can also search for this author inPubMed Google Scholar * Yinan Zhang View author publications You can also search for this author inPubMed Google

Scholar * Mingwen Zhang View author publications You can also search for this author inPubMed Google Scholar * Wei Zeng View author publications You can also search for this author inPubMed 

Google Scholar * Xuetao Gan View author publications You can also search for this author inPubMed Google Scholar * Dong Mao View author publications You can also search for this author

inPubMed Google Scholar * Fajun Xiao View author publications You can also search for this author inPubMed Google Scholar * Ting Mei View author publications You can also search for this

author inPubMed Google Scholar * Weiyao Zhao View author publications You can also search for this author inPubMed Google Scholar * Xiaolin Wang View author publications You can also search

for this author inPubMed Google Scholar * Min Gu View author publications You can also search for this author inPubMed Google Scholar * Jianlin Zhao View author publications You can also

search for this author inPubMed Google Scholar CONTRIBUTIONS H.L. conceived the idea, carried out numerical simulations, theoretical calculations, structure fabrication, material/structure

characterization and analysis of results, drew the figures, and wrote the manuscript text. Y.Z. conducted the reflection spectra measurements and discussed the results. Z.Y. and W.Z.

fabricated the Sb2Te3 single crystal and discussed the characterization. Y.L. participated in the fabrication and characterization of nanostructures. M.Z. conducted the exfoliation and

transfer of MoS2. W.Z. took part in the measurement of the Sb2Te3 relative permittivity. X.G., D.M., F.X., T.M., X.W., M.G., and J.Z. discussed the results and promoted the manuscript

presentation. All authors substantially contributed to the manuscript. CORRESPONDING AUTHORS Correspondence to Hua Lu, Yinan Zhang or Jianlin Zhao. ETHICS DECLARATIONS CONFLICT OF INTEREST

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http://creativecommons.org/licenses/by/4.0/. Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Lu, H., Yue, Z., Li, Y. _et al._ Magnetic plasmon resonances in nanostructured

topological insulators for strongly enhanced light–MoS2 interactions. _Light Sci Appl_ 9, 191 (2020). https://doi.org/10.1038/s41377-020-00429-x Download citation * Received: 02 June 2020 *

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