J. M. Ziman

Bio: J. M. Ziman is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 32 citations.

Electronic structure and carrier mobility in graphdiyne sheet and nanoribbons: theoretical predictions

Abstract: Using density functional theory coupled with Boltzmann transport equation with relaxation time approximation, we investigate the electronic structure and predict the charge mobility for a new carbon allotrope, the graphdiyne for both the sheet and nanoribbons. It is shown that the graphdiyne sheet is a semiconductor with a band gap of 0.46 eV. The calculated in-plane intrinsic electron mobility can reach the order of 10(5) cm(2)/(V s) at room temperature, while the hole mobility is about an order of magnitude lower.

Dynamics of Coherent Anharmonic Phonons in Bismuth Using High Density Photoexcitation

Abstract: We have investigated the dynamical properties of the coherent anharmonic phonons generated in Bi under high density excitation. The time-resolved reflectivity in the intensely photoexcited Bi film is modulated by the coherent A(1g) phonon oscillation with a time-dependent oscillation period. As the pump power density is increased, the line shape of the A(1g) mode in the Fourier transformed spectra becomes asymmetric, and the redshift of the phonon frequency is observed. Analysis of the transient redshift with a wavelet transform reveals that the frequency of the A(1g) mode depends on the squared amplitude of the oscillation, which is attributed to an anharmonicity of the lattice potential.

Design of Tunneling Field-Effect Transistors Based on Staggered Heterojunctions for Ultralow-Power Applications

Abstract: This letter presents the design of a tunneling FET with III-V-based tunnel heterojunctions for operation in digital circuits with supply voltages as low as 0.3 V. A representative implementation is predicted to achieve an on-state current drive of 0.4 mA/?m with an off-state current of 50 nA/?m. Comparison with homojunction counterparts reveals that the hetero-tunnel-junction implementations may address better the design tradeoff between on-state drive and off-state leakage.

On the thermodynamic limit for Hartree–Fock type models

Abstract: We continue here our study [10–13] of the thermodynamic limit for various models of Quantum Chemistry, this time focusing on the Hartree–Fock type models. For the reduced Hartree–Fock models, we prove the existence of the thermodynamic limit for the energy per unit volume. We also define a periodic problem associated to the Hartree–Fock model, and prove that it is well-posed.

Ferroelectricity in free niobium clusters.

Abstract: Electric deflections of gas-phase, cryogenically cooled, neutral niobium clusters [NbN; number of atoms (N) = 2 to 150, temperature (T) = 20to 300kelvin], measured in molecular beams, show that cold clusters may attain an anomalous component with very large electric dipole moments. In contrast, room-temperature measurements show normal metallic polarizabilities. Characteristic energies kBTG(N) [Boltzmann constant kB times a transition temperature TG(N)] are identified, below which the ferroelectric-like state develops. Generally, TG decreases [110 > TG(N) > 10K] as N increases, with pronounced even-odd alternations for N > 38. This new state of metallic matter may be related to bulk superconductivity.