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Effect of the Diamagnetic term in the ultra-strong coupling regime
摘要： We consider a set of two level atoms interacting with a single quantized bosonic mode governed by the Dicke model. In this model it is well known that under a critical value of the light-matter coupling a spontaneous radiation process takes place. In the present work, we investigate the dynamics of the system and we study the Wigner distribution function to visualize the effect of the minimal coupling on the ground state wavefunction from the normal phase to the superradiant one. We show also that the entanglement of Bi-partite model is limited by the presence of the diamagnetic term.
关键词： diamagnetic term,Circuit QED,Cavity QED,Entanglement
更新于2025-09-23 15:22:29
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Colossal dielectric, relaxor ferroelectric, diamagnetic and weak ferromagnetic properties of NdCrO3 perovskite nanoparticles
摘要： The NdCrO3 perovskite nanoparticles have been successfully synthesized using sol–gel auto-combustion process. Structural and morphological characterizations of the material have been performed at room temperature using XRD and SEM, respectively. Frequency- and temperature-dependent dielectric measurements have been performed in the range of 1 Hz–10 MHz and RT - 300 °C, respectively. The dielectric constant is found to be in the order of e0 > 103 at room temperature, indicating the colossal dielectric constant behaviour. Ferroelectric phase transition temperature has increased with an increase in frequency, suggesting that the material is a relaxor ferroelectric nature. Temperature- and field-dependent magnetization measurements have been carried out in the temperature range (5–400 K) and field up to 5 T. M–T curve exhibited a diamagnetic-like behaviour in low temperature and low fields. Two magnetic transitions were found at TN1 (223 K) and TN2 (33 K) which correspond to para to weak ferromagnetic transition and Nd3+ spin ordering, respectively. Hysteresis loop noticed weak ferromagnetism.
关键词： weak ferromagnetic properties,relaxor ferroelectric,Colossal dielectric,diamagnetic,NdCrO3 perovskite nanoparticles
更新于2025-09-23 15:19:57
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Anisotropies of the g-factor tensor and diamagnetic coefficient in crystal-phase quantum dots in InP nanowires
摘要： Crystal-phase low-dimensional structures offer great potential for the implementation of photonic devices of interest for quantum information processing. In this context, unveiling the fundamental parameters of the crystal phase structure is of much relevance for several applications. Here, we report on the anisotropy of the g-factor tensor and diamagnetic coefficient in wurtzite/zincblende (WZ/ZB) crystal-phase quantum dots (QDs) realized in single InP nanowires. The WZ and ZB alternating axial sections in the NWs are identified by high-angle annular dark-field scanning transmission electron microscopy. The electron (hole) g-factor tensor and the exciton diamagnetic coefficients in WZ/ZB crystal-phase QDs are determined through micro-photoluminescence measurements at low temperature (4.2 K) with different magnetic field configurations, and rationalized by invoking the spin-correlated orbital current model. Our work provides key parameters for band gap engineering and spin states control in crystal-phase low-dimensional structures in nanowires.
关键词： g-factor tensor,crystal-phase quantum dot,InP NWs,diamagnetic coefficient
更新于2025-09-19 17:13:59
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Exact ground state solution of shallow hydrogenic impurity states of a spherical parabolic GaAs/InAs quantum dot
摘要： The ground state spin magnetic moment current, binding energy, wave function and diamagnetic susceptibility of a shallow hydrogenic impurity located at the center of a parabolic spherical quantum dot are calculated analytically as a function of the dot size, interaction strength and confinement frequency. For comparison purposes, the results are discussed in the presence and in the absence of an impurity. Also, the dependence of the spin magnetic moment current on the spherical coordinates are derived, it is found that the spin magnetic moment current exhibits a peak structure and this current has a pronounced maximum for both small dot sizes and in the absence of impurities. Our results show that the impurities ground state binding energy enhances as the dot dimension decreases and depends strongly on the interaction strength as the dot size increases and reduces to zero in the bulk limit for large dimension of the dot. Moreover, the harmonic interaction has a strong influence on the diamagnetic susceptibility when the dot size increases where it decreases sharply in the presence of impurities while in the absence of impurities it decreases smoothly. In addition, the intensity of the magnetic field created by the spin magnetic moment current at the center of the quantum dot has been calculated. It is concluded that there is a critical value for characteristic parameters and the dot size for each type of semiconductor QD to give a specific function that might be important for nanotechnology manufacturing techniques.
关键词： Spherical quantum dot,Diamagnetic susceptibility,Harmonic e-e interaction,Donor impurity,Spin magnetic moment current
更新于2025-09-19 17:13:59
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Temperature effect on the binding energy and the diamagnetic susceptibility of a magneto-donor in Cylindrical Quantum Dot (GaAs/GaAlAs)
摘要： In this work, the effect of the temperature on the binding energy and the diamagnetic susceptibility of a shallow magneto-donor confined to move in a cylindrical quantum dot made out of GaAs/GaAlAs is studied within the effective mass approximation. We describe the quantum confinement by an infinite deep potential. The results show that when the temperature or the magnetic field increases, (i) the binding energy increases and (ii) the absolute value of the diamagnetic susceptibility decreases. Its effects depend strongly on the size of the CQD.
关键词： GaAs/GaAlAs,temperature effect,binding energy,cylindrical quantum dot,diamagnetic susceptibility,magneto-donor
更新于2025-09-19 17:13:59
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Single-particle-picture breakdown in laterally weakly confining GaAs quantum dots
摘要： We present a detailed investigation of different excitonic states weakly con?ned in single GaAs/AlGaAs quantum dots obtained by the Al droplet-etching method. For our analysis we make use of temperature-, polarization-, and magnetic-?eld-dependent μ-photoluminescence measurements, which allow us to identify different excited states of the quantum dot system. Besides that, we present a comprehensive analysis of g-factors and diamagnetic coef?cients of charged and neutral excitonic states in Voigt and Faraday con?guration. Supported by theoretical calculations by the con?guration-interaction method, we show that the widely used single-particle Zeeman Hamiltonian cannot be used to extract reliable values of the g-factors of the constituent particles from excitonic transition measurements.
关键词： g-factors,diamagnetic coefficients,quantum dots,exciton,Zeeman effect
更新于2025-09-16 10:30:52
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Influence of electric field on direct and indirect exciton in a concentrically coupled quantum ring heterostructure embedded in SiO2 matrix
摘要： Excitonic states of Concentric Double Quantum Ring (CDQR) heterostructures embedded in SiO2 matrix under the influence of electric field has been calculated theoretically using variational technique. CDQR has been confined in a quantum well of suitable width which serve as the height of the quantum ring along which the electric field is applied. Central barrier width, outer ring width and carrier location has been tuned to understand the localization of both direct and indirect excitons. Effect of ring dimension and electric field on the energy states of Inner Ring Exciton (IRE) and Outer Ring Exciton (ORE) has been determined. Tilting of conduction and valence bands due to the application of electric field invokes a triangular confinement to the carriers and the same has been discussed. Diamagnetic susceptibility which is merely an indicator of electron hole separation and intersubband transition energy has also been calculated for both symmetric and asymmetric quantum ring. Height of the QR has also been changed to study its effect on the diamagnetic susceptibility of an exciton.
关键词： Diamagnetic Susceptibility,Quantum Ring,Exciton,Binding energy,Electric Field
更新于2025-09-12 10:27:22
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Effect of confinement potential shape on the electronic, thermodynamic, magnetic and transport properties of a GaAs quantum dot at finite temperature
摘要： The effect of the shape of the confinement potential on the electronic, thermodynamic, magnetic and transport properties of a GaAs quantum dot is studied using the power-exponential potential model with steepness parameter p. The average energy, heat capacity, magnetic susceptibility and persistent current are calculated using the canonical ensemble approach at low temperature. It is shown that for soft confinement, the average energy depends strongly on p while it is almost independent of p for hard confinement. The heat capacity is found to be independent of the shape and depth of the confinement potential at low temperatures and for the magnetic field considered. It is shown that the system undergoes a paramagnetic-diamagnetic transition at a critical value of the magnetic field. It is furthermore shown that for low values of the potential depth, the system is always diamagnetic irrespective of the shape of the potential if the magnetic field exceeds a certain value. For a range of the magnetic field, there exists a window of p values in which a re-entrant behavior into the diamagnetic phase can occur. Finally, it is shown that the persistent current in the present quantum dot is diamagnetic in nature and its magnitude increases with the depth of the dot potential but is independent of p for the parameters considered.
关键词： transport properties,thermodynamic properties,canonical ensemble approach,electronic properties,quantum dot,GaAs,paramagnetic-diamagnetic transition,persistent current,magnetic properties,power-exponential potential model,confinement potential
更新于2025-09-11 14:15:04
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The structure, spectra and properties of Dy2O3 modified diamagentic lead-bismuth-germanium glasses
摘要： Dy2O3 is potential and attractive as scintillator, mid infrared laser and Faraday rotation materials in high energy physics, general radiation and magneto optical sensing systems. In this study, Dy3+ doped diamagnetic glasses with compositions of 10GeO2 – 30PbO – 50Bi2O3 – (10-x)B2O3 –xDy2O3 (x = 0, 0.5, 1, 2, 3, 5 M %) were fabricated by a melt quenching technique. The modification of Dy3+on glass forming, structure, UV–Vis, FT-IR, Raman and photoluminescence spectra and properties were investigated through XRD, Raman spectra, DSC, Vicker's hardness and Verdet constant measurements etc. Melt with Dy2O3 content beyond 5% prefer to crystallize, not to form glassy matrix. The UV visible absorption spectra showed three intense bands at 483 nm, 575 nm and 661 nm due to 4F9/2 → 6H15/2 (blue), 4F9/2 → 6H13/2 (yellow) and 4F9/2 → 6H11/2 (red) transitions, respectively. Judd-Ofelt paramaters have been calculated to verify network connectivity of Dy2O3 doped glasses. FT-IR and Raman spectrum depicted the presence of PbO4, BiO3, GeO6, BO3 frame groups and DyeO bonds from cubit Dy2O3. Glass doped with 1%Dy2O3 exhibited promising thermal stability (97 °C), microhardness (480 HV) and magneto-optical activity (0.1864 min/G.cm@532 nm) due to the high optical dispersion, high ion polarizability of Dy3+ ions
关键词： Heavy metal oxide glass,Faraday rotation,Dy2O3,Diamagnetic glass
更新于2025-09-04 15:30:14