Decay channels of gap plasmons in STM tunnel junctions

Lu, Yaoqin; Chen, Yuntian; Xu, Jing; Wang, Tao; Lü, Jing-Tao

doi:10.1364/oe.26.030444

Cited by 3 publications

(3 citation statements)

References 50 publications

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“…It is also worth mentioning that Gaussian bumps generated by rough substrates may be of a few nm size [24]. The diameter of an STM tip being in the range of a few nm to 50 nm [38][39][40],…”

Section: A Modelmentioning

confidence: 99%

Electron transport properties of graphene nanoribbons with Gaussian deformation

2020

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Gaussian deformation in graphene structures exhibits an interesting effect in which flowershaped confinement states are observed in the deformed region [Carrillo-Bastos et al., Phys. Rev. B 90 041411 (2014)]. To exploit such a deformation for various applications, tunable electronic features including a bandgap opening for semi-metallic structures are expected.Besides, the effects of disorders and external excitations also need to be considered. In this work, we present a systematic study on quantum transport of graphene ribbons with Gaussian deformation. Different levels of deformation are explored to find a universal behavior of the electron transmission. Using a tight-binding model in combination with Non-Equilibrium Green's Functions formalism, we show that Gaussian deformation influences strongly the electronic properties of ribbons in which the electron transmission decreases remarkably in high energy regions even if small deformations are considered. Interestingly, it unveils that the first plateau of the transmission of semi-metallic armchair ribbons is just weakly affected in the case of small deformations. However, significant large Gaussian bumps can induce a strong drop of this plateau and a transport gap is formed. The transmission at the zero energy is found to decrease exponentially with increasing the size of the Gaussian bump. Moreover, the gap of semi-conducting ribbons is enlarged with large deformations. The opening or the widening of the transport gap in large deformed armchair structures is interpreted by a formation of a threezone behavior along the transport direction of the hopping profile. On the other hand, a transport gap is not observed in zigzag ribbons regardless of the size of Gaussian bumps. This behavior is due to the strong localization of edge states at the energy point E = 0. Furthermore, under the effect of a positive vertical electric field +Ez, it shows an enhancement of electron transport in the conduction region and a suppression in the valence one. The effect of a negative field -Ez is reverse. Additionally, it is also pointed out that the electronic behavior of a Gaussian deformed

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Section: A Modelmentioning

confidence: 99%

Electron transport properties of graphene nanoribbons with Gaussian deformation

2020

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“…The magnitude of the parameters are selected as follows: (1) The bimodal emission requires that the energy levels of the two defect states are located between the chemical potentials of the tip and substrate. Therefore, we set μ t < ε d 2 < ε d 1 < μ s and ℏω 0 = ε d 1 – ε d 2 ; (2) The angular frequency ω p and the damping γ dp / pe (including radiative and nonradiative parts) of plasmon, the temperature T , and the bias voltage V ts between the tip and substrate are taken according to the experiment; (3) The plasmon modes are mainly coupled to the STM tip rather than radiation field, which indicates that radiative dissipation of plasmon is smaller than nonradiative dissipation, such that γ dp < γ pe . Similarly, we set γ d 0 < γ 0 e ; (4) The couplings (such as Γ tm /Γ ms , t ts , m p / m p 1 , m 0 , and m 0 p ) are adjustable parameters.…”

Section: Resultsmentioning

confidence: 99%

“…(2) The angular frequency ω p and the damping γ dp/pe (including radiative and nonradiative parts) of plasmon, the temperature T, and the bias voltage V ts between the tip and substrate are taken according to the experiment; 34 (3) The plasmon modes are mainly coupled to the STM tip rather than radiation field, 50 which indicates that radiative dissipation of plasmon is smaller than nonradiative dissipation, such that γ dp < γ pe . Similarly, we set γ d0 < γ 0e ; (4) The couplings (such as Γ tm /Γ ms , t ts , m p /m p1 , m 0 , and m 0p ) are adjustable parameters.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Mechanism of Bimodal Light Emission in a Molecule-Mediated Scanning Tunneling Microscopy Junction

Nian

Lü

2019

J. Phys. Chem. C

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We simulate the light emission from C 60 films driven by the tunneling electrons injected from a scanning tunneling microscope (STM) tip. Considering a model Hamiltonian which contains electron−photon and exciton−plasmon interactions, the emission spectrum is calculated by using the nonequilibrium Green's function method. Our simulations indicate that the two emission channels induced by the exciton and gap plasmon are almost independent in such a system, which gives rise to a bimodal-shaped light emission, and the emission ratio between the two channels can be controlled by varying the position of the STM tip. These results are consistent with recent experimental observations. Furthermore, the light emission is shown to be sensitive to the energy detuning and the bias voltage. The connection between bimodal and typical Fano line shape is also clarified. In particular, the stronger Purcell effect that is manifested by a significant enhancement of the spectrum in weak molecule−substrate coupling regime can be observed.

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Back focal plane imaging for light emission from a tunneling junction in a low-temperature ultrahigh-vacuum scanning tunneling microscope

Kuai

Fan

et al. 2023

Review of Scientific Instruments

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We report the design and realization of the back focal plane (BFP) imaging for the light emission from a tunnel junction in a low-temperature ultrahigh-vacuum (UHV) scanning tunneling microscope (STM). To achieve the BFP imaging in a UHV environment, a compact “all-in-one” sample holder is designed and fabricated, which allows us to integrate the sample substrate with the photon collection units that include a hemisphere solid immersion lens and an aspherical collecting lens. Such a specially designed holder enables the characterization of light emission both within and beyond the critical angle and also facilitates the optical alignment inside a UHV chamber. To test the performance of the BFP imaging system, we first measure the photoluminescence from dye-doped polystyrene beads on a thin Ag film. A double-ring pattern is observed in the BFP image, arising from two kinds of emission channels: strong surface plasmon coupled emissions around the surface plasmon resonance angle and weak transmitted fluorescence maximized at the critical angle, respectively. Such an observation also helps to determine the emission angle for each image pixel in the BFP image and, more importantly, proves the feasibility of our BFP imaging system. Furthermore, as a proof-of-principle experiment, electrically driven plasmon emissions are used to demonstrate the capability of the constructed BFP imaging system for STM induced electroluminescence measurements. A single-ring pattern is obtained in the BFP image, which reveals the generation and detection of the leakage radiation from the surface plasmon propagating on the Ag surface. Further analyses of the BFP image provide valuable information on the emission angle of the leakage radiation, the orientation of the radiating dipole, and the plasmon wavevector. The UHV–BFP imaging technique demonstrated here opens new routes for future studies on the angular distributed emission and dipole orientation of individual quantum emitters in UHV.

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Decay channels of gap plasmons in STM tunnel junctions

Cited by 3 publications

References 50 publications

Electron transport properties of graphene nanoribbons with Gaussian deformation

Electron transport properties of graphene nanoribbons with Gaussian deformation

Mechanism of Bimodal Light Emission in a Molecule-Mediated Scanning Tunneling Microscopy Junction

Back focal plane imaging for light emission from a tunneling junction in a low-temperature ultrahigh-vacuum scanning tunneling microscope

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