Charge-conservative Model Research Articles

A smoothed particle hydrodynamics method for two-phase electrohydrodynamics modeling with Nernst–Planck equations

The widely used leaky dielectric model often overlooks the rate of change in electric charges, leaving the impact of the charge conservation mechanism on two-phase electro-hydrodynamics (EHD) flows inadequately explored. In this study, we address this gap by introducing a charge-conservative model (CCM) for simulating such EHD systems within the framework of the smoothed particle hydrodynamics (SPH) method. Our methodology employs a fully explicit incompressible SPH (EISPH) approach to discretize the pressure Poisson, the electric potential Poisson, and the Nernst–Planck (N–P) equations. This work presents two notable contributions: (i) the introduction of the charge-conservative model into the incompressible SPH framework and (ii) the achievement of its discretization through a fully explicit methodology. To validate the proposed CCM, we conduct a comprehensive comparison with analytical solutions, as well as existing numerical and experimental results. The results affirm that the CCM consistently produces accurate outcomes across various test cases.

Symmetry classes, many-body zero modes, and supersymmetry in the complex Sachdev-Ye-Kitaev model

The complex Sachdev-Ye-Kitaev (cSYK) model is a charge-conserving model of randomly interacting fermions. The interaction term can be chosen such that the model exhibits chiral symmetry. Then, depending on the charge sector and the number of interacting fermions, level spacing statistics suggests a fourfold categorization of the model into the three Wigner-Dyson symmetry classes. In this work, inspired by previous findings for the Majorana Sachdev-Ye-Kitaev model, we embed the symmetry classes of the cSYK model in the Altland-Zirnbauer framework and identify consequences of chiral symmetry originating from correlations across different charge sectors. In particular, we show that for an odd number of fermions, the model hosts exact many-body zero modes that can be combined into a generalized fermion that does not affect the system's energy. This fermion directly leads to quantum-mechanical supersymmetry that, unlike explicitly supersymmetric cSYK constructions, does not require fine-tuned couplings, but only chiral symmetry. Signatures of the generalized fermion, and thus supersymmetry, include the long-time plateau in time-dependent correlation functions of fermion-parity-odd observables: The plateau may take nonzero value only for certain combinations of the fermion structure of the observable and the system's symmetry class. We illustrate our findings through exact diagonalization simulations of the system's dynamics.

Compact Modeling for Submicron Fully Depleted SOI MOSFET's

In this paper, we have developed a novel compact charge-conservative model for fully depleted silicon-on- -insulator MOSFETs and implemented it in SPICE3. Our model is valid for the DC, small-signal and large-signal simulations over a wide range of temperature. Simulations made using the model, following parameter extraction, are validated by comparison with experimental data. near subthreshold slope, increased saturation current and re- duced parasitic capacitances. Moreover, SOI MOSFETs are suitable in high temperature applications since they present a low leakage current and a reduced soft error ef- fect (1). Hence the availability of accurate fully depleted (FD) SOI MOSFET device model is suitable to both dig- ital and analog circuit simulation for the emerging SOI technology. To address this need, we propose in this paper a com- pact model for FD SOI MOSFETs in strong inversion. In this model, a linear relationship between the surface potential and the inversion charge density is used. The drain current and the total charges are written in terms of the inversion charge densities at the drain and source ends of the channel. The explicit unified expression of the inversion charge density is applied in these equa- tions (2, 3). Therefore, this model can be used to cal- culate the drain current and all large and small signal parameters since it includes threshold voltage roll-o, parasitic source/drain resistance eect, mobility reduc- tion due to the vertical field, carrier velocity saturation

A Unified Approach to Charge-Conservative Capacitance Modelling in HEMTs

The voltage dependence of high electron mobility transistor (HEMT) gate-source- and gate-drain capacitance is described by a set of equations based on a unified charge-conservative model approach. The model is applied to a low-noise GaAs pseudomorphic-HEMT (pHEMT) technology as well as its power variant. In terms of topology and parameters, the new expressions resemble the Curtice drain current model. They provide a globally accurate description of nonlinearities in HEMT capacitance