arXiv subjects

Shun-Cai Zhao

Publications and source records attributed to Shun-Cai Zhao.

At least 37 records · Page 2Linked to original sources

arXiv2024

Manipulative Properties of the Asymmetry Double Quantum Dots via Laser and Gate Voltage

We present the density matrix approach for theoretical description of an asymmetric double quantum dot(QD)system.The results show that the properties of gain,absorption and dispersion of the double QD system ,the population of the state with one hole in one dot and an electron in other dot transferred by tunneling can be manipulated by the laser pulse or gate voltage.Our scheme may propose a probability of electro-optical manipulation of quantum system.

quant-ph↗

arXiv2024

Effect of Spontaneously Generated Coherence and Detuning on 2D Atom Localization in Two Orthogonal Standing-Wave Fields

Two-dimensional (2D) atom localization via the spontaneously generated coherence (SGC) and detunings associated with the probe and standing-wave driving fields in a three-level V-type atomic system are investigated. In the gain process, two equal and tunable peak maxima of position distribution in the plane via the detunings are observed. However, one decreasing and the other increasing peak maxima in the absorption process via the SGC are achieved in the quadrants I and III of the x-y plane. A better resolution and more novelty for the 2D atom localization in our scheme are obtained.

quant-ph↗

arXiv2024

Left-handedness with three zero-absorption windows tuned by the incoherent pumping field and inter-dot tunnelings in a GaAs/AlGaAs triple quantum dots system

Left-handedness with three zero-absorption windows is achieved in a triple-quantum dot (TQD) system. With the typical parameters of a GaAs/AlGaAs heterostructure, the simultaneous negative relative electric permittivity and magnetic permeability are obtained by the adjustable incoherent pumping field and two inter-dot tunnelings. What's more, three zero-absorption windows in the left-handedness frequency bands are observed in the TQD system. The left-handedness with zero-absorption in solid state heterostructure may solve not only the challenge in the photonic resonant scheme for left-handed materials (LHMs) but also the application limitation of the negative refractive materials with large amount of absorption.

quant-ph↗

arXiv2024

Negative refraction index manipulated by a displaced squeezed Fock state in the mesoscopic dissipative left-handed transmission line

Negative refractive index (NRI) of the mescopic dissipative left-handed transmission line (LHTL) is manipulated by the displaced squeezed Fock state (DSFS) and the dissipation presented by the resistance and conductance. Comparing to the classical LHTL, some specific quantum characteristics are shown in the LHTL because of quantum effect, which will be significant to its miniaturization application in microwave frequency.

quant-ph↗

arXiv2024

2-D isotropic negative refractive index in a N-type four-level atomic system

2-D(Two-dimensional) isotropic negative refractive index (NRI) is explicitly realized via the orthogonal signal and coupling standing-wave fields coupling the N-type four-level atomic system. Under some key parameters of the dense vapor media, the atomic system exhibits isotropic NRI with simultaneous negative permittivity and permeability (i.e. Left-handedness) in the 2-D x-y plane. Compared with other 2-D NRI schemes, the coherent atomic vapor media in our scheme may be an ideal 2-D isotropic NRI candidate and has some potential advantages, significance or applications in the further investigation.

quant-ph↗

arXiv2024

Negative refraction without absorption via both coherent and incoherent fields in a four-level left-handed atomic system

This paper attempts a probe into negative refraction without absorption by means of an incoherent pump field and a strong coherent field coupling the dense four-level atomic system.With the application of the incoherent pump field to manipulate the populations in atomic levels and the variable strong coherent field to create quantum coherence, the constraint condition of two equal transition frequencies responding to the probe field in the atomic system isn't required.And these lead to the propagation transparency and strong magnetic response of the probe field,left-handedness with vanishing absorption in the atomic system.However,an excessive coherent field intensity would increase the absorption.

quant-ph↗

arXiv2024

Effect of spontaneously generated coherence on left-handedness in a degeneracy atomic system

A theoretical investigation is carried out into the effect of spontaneously generated coherence(SGC) on the left-handedness in a four-level Y-type atomic system with two highest nearly degenerate lying levels. It is found, with the spontaneously generated coherence intensity enhancing, the atomic system gradually displays left-handedness with simultaneous negative permittivity and permeability. And the refractive index enhances with the increasing intensity of SGC.However, the absorption is suppressed by the SGC effect when the SGC has a large intensity.When the probe field is near-resonant coupled to the atomic system, the appearance of SGC doesn't always change the permeability from positive to negative and allow for left-handed behavior,unless the SGC reaches a large intensity.

quant-ph↗

arXiv2024

Localization of cold $^{87}Rb$ atom within half-wavelength domain

Simulating the cold $^{87}Rb$ atom with a three-level quantum system interacting with two orthogonal standing-wave fields, the localization within half-wavelength domain in the x-y plane is achieved by monitoring the probe absorption. Within the half-wavelength domain, the single absorption peak increases from 0.2 to 1.0 via the spontaneously generated coherence (SGC), while the diameters of the single absorption peaks are diminished by the increasing incoherent pumping field. Our scheme provides the flexible parameters manipulating manner for the localization of cold $^{87}Rb$ atom.

quant-ph↗

arXiv2024

Enhanced quantum yields and efficiency in a quantum dot photocell modeled by a multi-level system

To absorb the photons below the band-gap energy effectively, we proposed a quantum dot (QD) photocell modeled by multi-level system for the quantum yields and photo-to-charge efficiency limits. The theoretical results show the quantum yields are enhanced as compared to the single band-gap solar cell, and the photo-to-charge efficiencies are larger than Shockley and Queisser efficiency in the same absorbed spectrum. What's more, at the room temperature the efficiency limits are well beyond 63% achieved by Luque and Marti (Ref\cite{26}) due to absorbing the low-energy photons via two sub-bands in this proposed photocell system. The achievements may reveal a novel theoretical approach to enhance the QD photocell performance modeled a multi-level absorbing photons system.

cond-mat.mes-hall↗

arXiv2024

Photovoltaic performances in a cavity-coupled double quantum dots photocell

Revealing the quantum regime of photovoltaics is crucial to enhancing the internal quantum efficiency of a double quantum dots (DQDs) photocell housed in a cavity. In this study, the performance of a quantum photovoltaic is evaluated based on the current-voltage and power-voltage characteristics in a cavity-coupled DQDs photocell. The results show that the cavity-DQDs coupling coefficient plays a dissipative role in the photovoltaic performance, and the cavity has a limited size for the photovoltaic performance. Additionally, more low-energy photons are easily absorbed by this cavity-coupled DQDs photocell compared with the case without cavity. These results may provide some strategies for improving the photoelectric conversion efficiency and internal quantum efficiency of cavity-coupled DQDs photocells.

cond-mat.mes-hall↗

arXiv2024

Algebraic analysis of electromagnetic chirality-induced negative refractive index in a four-level atomic system

This paper presents a algebraic analysis of electromagnetic chirality-induced negative refractive index in a four-level atomic medium. According to analyze mathematically its argument of the complex refractive index for one circular polarization, it found that the negative refractive index without simultaneously negative permittivity and permeability can be obtained when the argument is in the second quadrant of the cartesian coordinate system, and that the probe field coupling to two equal transition frequencies in the atomic level doesn't require. This undoubtedly reduced stringent conditions to negative refractive index by quantum optics. As an application, our scheme may possibly give a novel approach to obtain negative refractive index by electromagnetic chirality-inducing.

quant-ph↗

arXiv2024

Predicting quantum evolutions of excitation energy transfer in a light-harvesting complex using multi-optimized recurrent neural networks

Constructing models to discover physics underlying magnanimous data is a traditional strategy in data mining which has been proved to be powerful and successful. In this work, a multi-optimized recurrent neural network (MRNN) is utilized to predict the dynamics of photosynthetic excitation energy transfer (EET) in a light-harvesting complex. The original data set produced by the master equation were trained to forecast the EET evolution. An agreement between our prediction and the theoretical deduction with an accuracy of over 99.26\% is found, showing the validity of the proposed MRNN. A time-segment polynomial fitting multiplied by a unit step function results in a loss rate of the order of $10^{-5}$, showing a striking consistence with analytical formulations for the photosynthetic EET. The work sets up a precedent for accurate EET prediction from large data set by establishing analytical descriptions for physics hidden behind, through minimizing the processing cost during the evolution of week-coupling EET.

physics.app-ph↗

arXiv2024

Left-handedness in the balanced/unbalanced resonance conditions of a quantized composite right-left handed transmission line

Left-handedness signifies negative permittivity ($\varepsilon_r$) and permeability ((μ_r)) in the same frequency band. The $\varepsilon_r$ and $μ_r$ are evaluated in a quantized composite right-left handed transmission line (CRLH-TL), and the frequency band for left-handedness is also valuated in the balanced resonance ($ L_r C_l = L_l C_r $) and unbalanced resonance($L_l C_r \neq L_r C_l$) cases in the displaced squeezed Fock state. The results show that the balanced resonance plays an important role in bandwidth and achieving for left-handedness. These displays some quantum mechanical behaviors and proposes a new potential approach to wider frequency band left-handedness for the quantized CRLH-TL.

physics.app-ph↗

arXiv2024

Quantum entropy evolution in the photovoltaic process of a quantum dot photocell

For efficient photovoltaic conversion, it is important to understand how quantum entropy-related quantities evolve during the photovoltaic process. In this study, using a double quantum dot (DQD) photocell model, we explored the dynamic quantum entropy-related parameters during the photovoltaic output. The findings demonstrate that the dynamic photovoltaic performance is compatible with quantum entropy-related parameters with varying tunneling coupling strengths, but at varied ambient temperatures, an opposing relationship is discovered between them. Hence, some thermodynamic criteria may be used to evaluate the photovoltaic process in this proposed photocell model. This work's merits include expanding our understanding of photoelectric conversion from a thermodynamic perspective as well as perhaps suggesting a new thermodynamic approach to efficient photoelectric conversion for DQD photocells.

cond-mat.mes-hall↗

arXiv2024

High quantum yields generated by a multi-band quantum dot photocell

We perform the quantum yields in a multi-band quantum dot (QD) photocell via doping an intermediate band (IB) between the conduction band (CB) and valence band (VB). Under two different sub-band gap layouts, the output power has a prominent enhancement than the single-band gap photocell and the achieved peak photo-to-charge efficiency reaches to 74.9% as compared to the limit efficiency of 63.2% via the IB approach in the theoretical solar cell prototype. The achieved quantum yields reveal the potential to improve efficiency by some effective theoretical approaches in the QD-IB photocell.

cond-mat.mes-hall↗

arXiv2024

Negative refraction with little loss manipulated by the voltage and pulsed laser in double quantum dots

The paper demonstrates that negative refractive index can be achieved via tuning the tunneling rate between a double quantum dots(QDs) system by applying a bias voltage, and a pulsed laser. As the bias voltage being changed, the refraction index can be tunable to negative with the simultaneous negative permittivity and permeability. While the varying pulsed laser is applied to the double QDs system, moreover, the negative refractive index with little loss can be obtained. The flexible manipulation on a solid state system to realize negative refraction may give a new way for experimental research in the future.

physics.optics↗

arXiv2024

Dual peaks evoluting into single-peak for sub-wavelength 2-D atom localization in a V-type atomic system

The atom localization of a V-type atomic system is discussed by the detunings associated with the probe and the two orthogonal standing-wave fields, and by the spontaneously generated coherence (SGC). Within the half-wavelength domain in the 2-dimensional(2-D) plane, the atom localization depicted by the probe dual absorption peaks is achieved when the detunings are tuned. However, the dual peaks change into single-peak when the SGC arises. The single-peak 2-D localization demonstrated the advantage for atom localization achieved by the flexible manipulating parameters in our scheme.

quant-ph↗

arXiv2024

Photovoltaic properties enhanced by the tunneling effect in a coupled quantum dot photocell

Double quantum dots (DQDs) have emerged as versatile and efficient absorbing light devices owing to their more multiple adjusting parameters than the single QD's. Using the system-reservoir theory, tunneling effect on the quantum photovoltaic properties is evaluated detailedly in a DQDs photocell with different energy mismatches under different temperatures. Repopulation of photo-generated carriers in two excited states is generated by electron tunneling effect between two coupled QD pairs, which brings out more efficient quantum photovoltaic yields evaluated by the short-circuit current, open-circuit voltage and output power through the current-voltage and power-voltage characteristics. Further discussion reveals that the quantum photovoltaic properties are enhanced by the ambient environment temperatures but weakened by the energy mismatches. However, the weakening effect caused by the energy mismatches can be greatly reduced by tunneling effect. Insights into tunneling effect between two adjacent QD not only facilitate a better understanding of the fundamentals in carriers transport, but also provide novel strategies for efficient artificial assembled QD arrays photocell inspired by this proposed DQDs photocell model.

cond-mat.mes-hall↗