A method for analyzing the coupling relationship between optical phonons and charge carriers based on transient observation techniques

Abstract

This invention relates to the field of ultrafast detection technology, specifically to a method for analyzing the coupling relationship between optical phonons and charge carriers based on transient observation technology. The specific technical solution is as follows: (1) Using supercontinuous white light transmission-pumped detection, a few-layer two-dimensional transition metal selenide is tested to obtain broadband transient absorption data; (2) Dynamic curves at different detection wavelengths are extracted from the broadband transient absorption data; (3) The dynamics at different detection wavelengths are deconvolved and fitted with a triple exponential curve, and the coherent optical phonon oscillation signal is extracted by subtracting the fitted data from the original data; (4) The frequency and amplitude of the coherent optical phonon oscillation signal are extracted by periodically damped oscillation fitting; (5) A detection wavelength dependence diagram is plotted for the amplitude of coherent optical phonons at the same frequency. This invention, through the analysis of the detection wavelength dependence of optical phonon amplitude, obtains the coupling strength between optical phonons of different frequencies and charge carriers of different energy levels.

Description

Technical Field

[0001] This invention relates to the field of ultrafast detection technology, specifically to a method for analyzing the coupling relationship between optical phonons and charge carriers based on transient observation technology. Background Technology

[0002] Two-dimensional transition metal selenides generally possess excellent stability and optoelectronic and mechanical properties. For example, palladium diselenide and platinum diselenide have been shown to contain a variety of coherent phonons within their materials. The coupling relationship between charge carriers and phonons makes them highly promising for applications in optoelectronic devices such as high-frequency communication and ultrafast topological switches, attracting widespread attention from scientists in recent years. However, traditional techniques cannot directly observe the coupling between coherent phonons and charge carriers within these materials. This results in a very limited understanding of the complex transient coupling processes involving light, sound, electricity, and force in two-dimensional transition metal selenides, severely restricting the development of optoelectronic devices based on these materials. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for analyzing the coupling relationship between optical phonons and charge carriers based on transient observation technology.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention discloses a method for analyzing the coupling relationship between optical phonons and charge carriers based on transient observation technology, comprising the following steps:

[0006] (1) A few-layer two-dimensional selenide sample is grown or transferred on a substrate; the substrate is a transparent silica material, so that the transmission pump detection experiment in step (2) can be carried out.

[0007] (2) The few-layer two-dimensional transition metal selenides were tested using supercontinuous white light transmission pump detection to obtain broadband transient absorption data; the detection range of supercontinuous white light was 380-800 nm.

[0008] (3) Extract the dynamic curves at different detection wavelengths from broadband transient absorption data. The dynamics at different detection wavelengths correspond to the carrier behavior at different excitation energy levels.

[0009] (4) Perform deconvolution triple-exponential fitting on the dynamics at different detection wavelengths, and extract the coherent optical phonon oscillation signal by subtracting the fitted data from the original data;

[0010] (5) The frequency and amplitude of coherent optical phonon oscillations are extracted by periodic damped oscillation fitting of the coherent optical phonon oscillation signal;

[0011] (6) The wavelength dependence diagram of the coherent optical phonon amplitude at the same frequency is plotted and analyzed as follows: The amplitude of the coherent optical phonon represents the coupling strength between the coherent optical phonon and carriers at different energy levels. The larger the oscillation amplitude, the higher the coupling degree.

[0012] The present invention has the following beneficial effects:

[0013] 1. This invention employs supercontinuous white light pump-probe to perform transient absorption tests on two-dimensional transition metal selenides (TMS). Phonon oscillation dynamics curves are then obtained by exponentially fitting the residuals. The coupling relationship between optical phonons and charge carriers is determined by comparing phonon amplitudes at different detection wavelengths. This method provides a simple, accurate, and rigorous testing and analysis scheme for determining the optical phonon-carrier coupling relationship in two-dimensional TMS thin films under various conditions, and it is universally applicable to two-dimensional TMS.

[0014] 2. This invention obtains the oscillation dynamics of optical phonons by extracting the residuals from the exponential fitting of transient absorption dynamics; further fitting the oscillation dynamics yields information such as the amplitude and frequency of optical phonons, thus realizing a simple, fast, and accurate method for determining the optical phonon parameters inside a material.

[0015] 3. By analyzing the wavelength dependence of optical phonon amplitude detection, this invention obtains the coupling strength between optical phonons of different frequencies and carriers of different energy levels, making the analysis method of this invention more scientific and rigorous. At the same time, this invention has universality for various two-dimensional transition metal selenides. Attached Figure Description

[0016] Figure 1 To test palladium diselenide using supercontinuous white light transmission-pumped detection, a broadband transient absorption map was obtained.

[0017] Figure 2 Optical phonon oscillation curves extracted from the residuals of the transient absorption kinetics exponential fitting.

[0018] Figure 3 The graph shows the dependence of optical phonon amplitude on detection wavelength for 4.5 THz and 0.38 THz. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0021] Example 1

[0022] Palladium diselenide was tested using supercontinuum white light transmission-pumped detection. The excitation wavelength was selected at 700 nm, and the detection wavelength range was between 380 nm and 800 nm, yielding a broadband transient absorption spectrum. Figure 1 As shown. The testing principle is as follows: using the excitation wavelength will excite the charge carriers from the ground state to different excited states. Then, when the probe light at the corresponding excited state energy level is used for detection, a negative signal will be obtained at the corresponding wavelength in the transient spectrum.

[0023] The dynamic curves of the negative signal at the peak position of 390 nm were extracted and subjected to exponential fitting. The difference between the fitted data and the original data was calculated to obtain the dynamic curves of two types of coherent phonon oscillations at the rising edge of the dynamic curve (0-2 ps) and the falling edge of the dynamic curve (2-10 ps), respectively. Figure 2 As shown, the two dynamic curves were fitted using a periodically damped oscillation model, yielding two optically coherent phonon frequencies: 4.5 THz and 0.38 THz. The amplitude at a detection wavelength of 390 nm was also obtained.

[0024] Dynamic curves were extracted at multiple wavelengths (390 nm, 411 nm, 458 nm, 525 nm, 580 nm, 639 nm, and 672 nm). Repeating the fitting process, the amplitude at each detection wavelength was obtained, thus yielding the amplitude variation curves of the two optical phonons with the detection wavelength. Figure 3 As shown, a larger amplitude indicates a stronger coupling between the optical phonon and the charge carriers at the energy level corresponding to that detection wavelength.

[0025] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for analyzing the coupling relationship between optical phonons and carriers based on transient observation technology, characterized in that: The method comprises the following steps: (1) testing a few-layer two-dimensional transition metal selenide by using supercontinuum white light transmission type pump detection to obtain wide-spectrum transient absorption data; (2) extracting kinetic curves at different probe wavelengths from the wide-spectrum transient absorption data, and the kinetics at different probe wavelengths correspond to the behaviors of carriers at different excitation energy levels; (3) performing three-index deconvolution fitting on the kinetics at different probe wavelengths, and extracting coherent optical phonon oscillation signals by subtracting the fitting data from the original data; (4) performing periodic damped oscillation fitting on the coherent optical phonon oscillation signals to extract coherent optical phonon frequencies and amplitudes; (5) making a probe wavelength dependence graph of the coherent optical phonon amplitudes at the same frequency, and the greater the oscillation amplitude, the higher the coupling strength between the coherent optical phonon and the carriers at different energy levels.

2. The method of claim 1, wherein: The few-layer two-dimensional transition metal selenide is grown on a substrate or transferred to a substrate.

3. The method of claim 2, wherein: The substrate is a silica transparent material.

4. The method of claim 1, wherein: In step (1), the probe range of the supercontinuum white light is 380-800 nm.

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