Resonantly driven exciton Rabi oscillation in single quantum dots emitting at 1300 nm

We report on the resonance fluorescence （RF） from single InAs quantum dots （QDs） emitting at the telecom band of 1300 nm. The InAs/GaAs QDs are embedded in a planar optical microcavity and the RF is measured by an orthogonal excitation-detection geometry for deeply suppressing the residual laser scattering. An ultra-weak He-Ne laser is necessary to be used as a gate laser for obtaining RE Rabi oscillation with more than one period is observed through the picosecond （ps） pulsed laser excitation. The resonant control of exciton opens up new possibilities for realizing the on-demand single photon emission and quantum manipulation of solid-state qubits at telecom band.

Quantum Coupling Effect between Quantum Dot and Quantum Well in a Resonant Tunneling Photon-Number-Resolving Detector

Excited states of lnAs quantum dots （QDs） can be energetically coupled with the confined level of OaAs quantum wells （QWs） in a thin-barrier resonant tunneling diode （RTD）. Single charge variation in the coupled QD can effectively switch on/off the resonant tunneling current passing through RTD, not only for emcient single-photon detection but also for photon-number-resolving detection. We present the study of the Q,D-QW coupling effect in the quantum dot coupled resonant tunneling diode （QD-cRTD） and figure out important factors for further improving the detector performance.

Controlling the Goos-H?nchen Shift via Incoherent Pumping Field and Electron Tunneling in the Triple Coupled InGaAs/GaAs Quantum Dots

We study the controlling of the Goos-Hanchen （GH） shifts in reflected and transmitted light beams in the triple coupled InGaAs/GaAs quantum dot （QD） nanostructures with electron tunneling and incoherent pumping field. It is shown that the lateral shift can become either large negative or large positive, which can be controlled by the electron tunneling and the rate of incoherent pump field in different incident angles. It is also demonstrated that the properties of the OH shifts are strongly dependent on the probe absorption beam of the intracavity medium due to the switching from superluminal light propagation to subluminal behavior or vice versa. Our suggested system can be considered as a new theoretical method for developing a new nano-optoelectronic sensor.

Optimal Performance Analysis of a Three-Terminal Thermoelectric Refrigerator with Ideal Tunneling Quantum Dots

The model of a three-terminal thermoelectric refrigerator with ideal tunneling quantum dots is established. It consists of a cavity connected to two quantum dots embedded between two electron reservoirs at different temperatures and chemical potentials. According to the Landauer formula the expressions for the heat current, the cooling rate and the coefficient of performance （COP） are derived analytically. The performance characteristic curves of the cooling rate versus the coefficient of performance are plotted with numerical calculation. The optimal regions of the cooling rate and the COP are determined. Moreover, we optimize the cooling rate and the COP with respect to the position of energy level of the right quantum dot, respectively. The influence of the width of energy level and the temperature ratio on performance of the three-terminal thermoelectric refrigerator is analyzed. Lastly, when the width of energy level is small enough, the optimal performance of the refrigerator is discussed in detail.

Tunneling current of the Coulomb-coupled quantum dots embedded in n-n junction

Taking account of the electron--electron （hole） and electron--hole interactions, the tunneling processes of the main quantum dot （QD） Coulomb-coupled with a second quantum dot embedded in n--n junction have been investigated. The eighteen resonance mechanisms involved in the tunneling processes of the system have been identified. It is found that the tunneling current depends sensitively on the electron occupation number in the second quantum dot. When the electron occupation number in the second dot is tiny, both the tunneling current peaks and the occupation number plateaus in the main QD are determined by the intra-resonance mechanism. The increase of the electron occupation number in the second dot makes the inter-resonance mechanism participate in the transport processes. The competition between the inter and intra resonance mechanisms persists until the electron occupation number in the second dot reaches around unity, leading to the consequence that the inter-resonance mechanisms completely dominate the tunneling processes.

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 system. With the typ- ical 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. Furthermore, three zero-absorption windows in the left-handedness frequency bands are observed. The left- handedness with zero-absorption in the solid state heterostrueture may solve the challenges not only in the left-handed materials achieved by the photonic resonant scheme but also in the application of negative refractive materials with a large amount of absorption.

Optically Modulated Bistability in Quantum Dot Resonant Tunneling Diodes

InAs quantum dots are introduced into resonant tunneling diodes to study the electronic transport behavior,and a wide bistability(ΔV~0.8 V)is observed in the negative differential resistance region.Based on an analytic model,we attribute the observed distinct bistability of a resonant tunneling diodes with quantum dots to the feedback dependence of energy of the electron-storing quantum dots on the tunneling current density.Meanwhile,we find that this wide bistable region can be modulated sensitively by light illumination and becomes narrower with increasing light intensity.Our results suggest that the present devices can be potentially used as sensitive photodetectors in optoelectronic fields.

Inter-Well Coupling and Resonant Tunneling Modes of Multiple Graphene Quantum Wells

We investigate the inter-well coupling of multiple graphene quantum well structures consisting of graphenesuperlattices with different periodic potentials.The general form of the eigenlevel equation for the bound states of thequantum well is expressed in terms of the transfer matrix elements.It is found that the electronic transmission exhibitsresonant tunneling peaks at the eigenlevels of the bound states and shifts to the higher energy with increasing the incidentangle.If there are N coupled quantum wells,the resonant modes have N-fold splitting.The peaks of resonant tunnelingcan be controlled by modulating the graphene barriers.

Spin-polarized current in double quantum dots

We analyze the transport through asymmetric double quantum dots with an inhomogeneous Zeeman splitting in the presence of crossed dc and ac magnetic fields. A strong spin-polarized current can be obtained by changing the dc magnetic field. It is mainly due to the resonant tunnelling. But for the ferromagnetic right electrode, the electron spin resonance also plays an important role in transport. We show that the double quantum dots with three-level mixing under crossed dc and ac magnetic fields can act not only as a bipolar spin filter but also as a spin inverter under suitable conditions.

Adaption of Au Nanoparticles and CdTe Quantum Dots in DNA Detection

一个 DNA 荧光探查系统基于荧光回声精力转移(烦恼) 从 CdTe 量点(QD ) 施主到 Au nanoparticle (AuNP ) 领受人被介绍。CdTe QD，作为精力施主，在直径的 2.5nm 在水里被准备。Au nanoparticles，作为精力领受人，在直径的 16nm 被减小从金氯化物准备。CdTe QD 通过 carbodiimide 水疗院氯化物(EDC ) 作为一个连接器，和 3'-SH-DNA 是的 1-ethyl-3-(dimethylaminopropyl ) 被连接到 5'-NH2-DNA 到 AuNPs 的表面上自我装配。绑在 QD 和 AuNPs (CdTe-dsDNA-Au ) 的互补双搁浅的 DNA (dsDNA ) 的杂交决定了 CdTe QD 和 Au nanoparticles 的 FRET 距离。比作 CdTe-DNA 的荧光， CdTe-DNA-Au 的荧光结合极其减少了，它显示 FRET 发生在 CdTe QD 和 Au nanoparticles 之间。这的荧光变化结合取决于 Au-DNA 的比率到 CdTe-DNA。当到 QD-DNA 比率的 AuNPs-DNA 是 10:1 时， FRET 效率到达了最大值。当互补单个搁浅的 DNA 被介绍进这个系统时，探查系统将有荧光恢复的某个度，它证明在 CdTe QD 和 Au nanoparticles 之间的距离被增加。

Charge noise acting on graphene double quantum dots in circuit quantum electrodynamics architecture

We investigate the dephasing mechanisms induced by the charge noise and microwave heating effect acting on a graphene double quantum dot （DQD） capacitively coupled to a microwave resonator. The charge noise is obtained from DC transport current, and its contribution to dephasing is simultaneously determined by the amplitude response of the microwave resonator. A lowfrequency 1/f-type noise is demonstrated to be the dominant factor of the dephasing of graphene DQD. Furthermore, when the applied microwave power is larger than -90 dBm, the dephasing rate of graphene DQD increases rapidly with the increase of microwave power, and fluctuates slightly with the applied microwave power smaller than -90 dBm. Our results can be applied to suppress the impeditive influence on the dephasing of graphene-based devices associated with microwave input in the perspective investigations.

Recent Progress in Optical Sensors Based on MXenes Quantum Dots and MXenes Nanosheets

In recent years,MXenes,as a new promising two-dimensional material,have received extensive attentions in the fields of environmental remediation,catalysts,sensors,and energy storage.To broaden the applications of MXenes in sensing,MXenes nanosheets(MNSs) and MXenes quantum dots(MQDs) are prepared by physical etching or chemical oxidation.MNSs are monolayered or multilayered MXenes nanosheets within several nanometers in height,and can serve as the perfect reaction substrate and fluorescence quencher.MQDs are spherical,fluorescent MXenes QDs within several nanometers in size,which possess favorable stability and photo stability.Since the distinct features such as high conductivity,favorable hydrophilicity,biocompatibility,abundant surface functional groups,and easy functionalization,MNSs and MQDs show potential applications in the fields of anti-counterfeiting,environmental monitoring,biosensing and biomedicine.This review focuses on the research of MNS s/MQDs-based optical sensors,including colorimetric sensors,fluorescence sensors,electrochemiluminescence sensors,surface plasmon resonance sensors,and surface-enhanced Raman scattering sensors.Furthermore,the current challenges and prospects concerning MNSs/MQDs-based optical sensing techniques are discussed.

Macroscopic resonant tunneling in an rf-SQUID flux qubit

We have observed the macroscopic resonant tunneling of magnetic flux between macroscopically distinct quantum states in a superconducting flux qubit. The dependences of the macroscopic resonant tunneling on the barrier height of the potential well, the flux bias and the initial state are investigated. Detailed measurements of the tunneling rate as a function of the flux bias reveal the feature of the quantum noise in the superconducting flux qubit.

Macroscopic resonant tunneling in an rf-SQUID flux qubit under a single-cycle sinusoidal driving

We experimentally demonstrate the observation of macroscopic resonant tunneling（MRT） phenomenon of the macroscopic distinct flux states in a radio frequency superconducting quantum interference device（rf-SQUID） under a singlecycle sinusoidal driving.The population of the qubit exhibits interference patterns corresponding to resonant tunneling peaks between states in the adjacent potential wells.The dynamics of the qubit depends significantly on the amplitude,frequency,and initial phase of the driving signal.We do the numerical simulations considering the intra-well and interwell relaxation mechanism,which agree well with the experimental results.This approach provides an effective way to manipulate the qubit population by adjusting the parameters of the external driving field.

Enhanced interfacial charge transfer on Bi metal@defective Bi_(2)Sn_(2)O_(7) quantum dots towards improved full-spectrum photocatalysis:A combined experimental and theoretical investigation

To mitigate the water pollution problem by photocatalytic degradation of typical antibiotics of tetracycline(TC),we prepared defective Bi_(2)Sn_(2)O_7(BSO)quantum dots(QDs)with a full spectral response due to Bi metal deposition,using a one-pot hydrothermal method,labeled as Bi@BSO-OV.The optimized Bi@BSOOV showed 73.4% removal of TC in 1 h under irradiation with a 50 W LED lamp in the wavelength band in the visible-near-infrared(vis-NIR)light,a rate that is substantially greater than that of pure BSO(14.7%).The synergistic interaction of Bi metal and oxygen vacancies(OVs)is crucial to boosting photocatalytic performance.The near-infrared region of the photo-response is extended by the surface plasmon resonance(SPR)effect of Bi metal,enhancing the photocatalytic performance and dramatically raising the efficiency of solar energy utilization.In addition to inducing defect levels in BSO,the OVs also activate the surface adsorbed O_(2) to promote the production of·O_(2)^(-)and ^(1)O_(2).DFT calculations reveal that Bi metal and OVs can mutually tune the charge transfer pathways.On the one hand,Bi metal can act as both a charge transfer bridge and an electron donor to assist charge separation.On the other hand,OVs-induced defect levels allow electrons that leap to the conduction band(CB)to first leap from the valence band(VB)to the defect levels,notably improving interfacial charge separation and transfer.The concept of design executed in this study for altering the catalyst by introducing both OVs and Bi metal can provide a rational design idea and potential insight for improving the photocatalytic activity for environmental applications.

INVESTIGATION ON RESONANT TUNNELING IN GaAs/Al_xGa_(1-x)As DBD USING TUNNELING SPECTROSCOPY

Experimental investigation on resonant tunneling in various GaAs/AlxGa1-xAsdouble barrier single well structures has been performed by using tunneling spectroscopy atdifferent temperatures.The results show that in addition to resonant tunneling via GaAs wellstate confined by AlxGa1-xAs Γ-point barrier there exists resonant tunneling via GaAs well stateconfined by AlxGa1-xAs X-point barrier for both indirect（x】0.4）and direct（x【0.4）cases.

Chemically derived graphene quantum dots for high-strain sensing

Graphene quantum dots(GQDs)refer to graphene fragments with a lateral dimension typically less than 100 nm,which possess unique electrical and optical properties due to the quantum confinement effect.In this study,we demonstrate that chemically derived graphene quantum dots show great potential for making highly stretchable and cost-effective strain sensors via an electron tunneling mechanism.Stretch-able strain sensors are critical devices for the field of flexible or wearable electronics which are expected to maintain function up to high strain values(>30%).However,strain sensors based on conventional materials(i.e.metal or semiconductors)or metal nanoparticles(e.g.gold or silver nanoparticles)only work within a small range of strain(i.e.the former have a working range<1%and the latter<3%).In this study,by simply dropcasting solution-processed GQDs between the interdigitated electrodes on polydimethylsiloxane,we obtained devices that can function in the range from 0.06%to over 50%ten-sile strain with both the sensitivity and working range conveniently adjustable by the concentration of GQDs applied.This study provides a new concept for practical applications of GQDs,revealing the poten-tial of this material for smart applications such as artificial skin,human-machine interfaces,and health monitoring.

Resonant tunneling and quantum fluctuation in a driven triple-well system

The influence of parameters such as the strength and frequency of a periodic driving force on the tunneling dynamics is investigated in a symmetric triple-well potential. It is shown that for some special values of the parameters, tunneling could be enhanced considerably or suppressed completely. Quantum fluctuation during the tunneling is discussed as well and the numerical results are presented and analysed by virtue of Floquet formalism.

Adjusting amplitude of the stored optical solitons by inter-dot tunneling coupling in triple quantum dot molecules

We study the propagation properties of a probe field in an aligned asymmetric triple quantum dot molecule with both sides inter-dot tunneling coupling effect. It is shown that the probe field can form optical soliton due to the destructive quantum interference induced by the quantum inter-dot tunneling coupling effect. Interestingly, these optical solitons can be stored and retrieved by adjusting single or double inter-dot tunneling coupling effect, different from that light memory in the ultra-cold atom system. Furthermore, we also find that the amplitude of the stored optical soliton can be adjusted by the strength of the single or double inter-dot tunneling coupling. It is possible to improve the stability and the fidelity of the optical information in the process of the storage and retrieval in semiconductor quantum dots devices.

Quantum well sub-bands probed by photo-excited, capacitance-sensitive resonant tunneling spectrum

By combining resonant tunneling spectra with capacitance-voltage (C-V) characteristics under photo-excitation, we have developed photo-excited, capacitance-sensitive resonant tunneling spectrum (PC-RTS) for probing the quantized levels of quantum wells in valence band. Inter-well tunneling events have been identified and are in good agreement with the calculated level scheme in the valence band of a quantum well-barrier-quantum well heterostructure. Compared to conventional resonant tunneling spectrum, our method shows remarkable advantages in higher sensitivity for discriminating electronic structures.