Effective mass (solid-state physics)

About: Effective mass (solid-state physics) is a research topic. Over the lifetime, 12539 publications have been published within this topic receiving 295485 citations.

Hybrid electronic properties between the molecular and solid state limits: Lead sulfide and silver halide crystallites

Abstract: Tiny single PbS crystals of ∼25 A diameter are synthesized and studied optically in low‐temperature colloidal solutions. Electron microscopic examination shows a simple cubic rock salt structure with a lattice constant unchanged, within experimental error, from the bulk value. These crystallites lack the near infrared electronic absorption characteristic of bulk PbS. The small crystallite absorbance in the visible rises more steeply than does the bulk absorbance. These results reflect electron and hole localization if one considers the variation in effective mass across the band structure. A simple discussion of localization anywhere in the Brillouin zone is given. For the first time, crystallite syntheses are carried out in solvent mixtures that form transparent glasses upon cooling. The PbS spectra are independent of temperature (at current experimental resolution) down to 130 K, in contrast to earlier results for quantum size exciton peaks in ∼20 A ZnS crystallites. Previously published observations of size dependence in the excited state electronic properties of AgI and AgBr are explained as consequences of electron and hole localization in the small crystallites. AgBr appears to be the first indirect gap semiconductor to be examined in the regime where bulk properties are not fully formed.

Ab initio calculations of the mechanical and electronic properties of strained Si nanowires

Abstract: This paper reports a systematic study of the mechanical and electronic properties of strained small diameter (0.7\char21{}2.6 nm) silicon nanowires (Si NWs) using ab initio density functional theory calculations. The values of Young's modulus, Poisson ratio, band gap, effective mass, work function, and deformation potentials are calculated for $⟨110⟩$ and $⟨111⟩$ Si NWs. We find that quantum confinement in $⟨110⟩$ Si NWs splits conduction band valleys and decreases transport effective mass compared to the bulk case. Consequently, additional tensile strain should not lead to further significant electron mobility improvement. An interesting finding we report in this paper is that under compressive strain, there is a dramatic decrease in deformation potentials of $⟨110⟩$ Si NWs, which may result in a strong increase in electron mobilities, despite a concurrent increase in effective mass. We also observe a similar strain-induced counterplay of hole deformation potentials and effective masses for both $⟨110⟩$ and $⟨111⟩$ Si NWs. Finally, we do not see any significant effect of tensile or compressive strain on electron effective masses and deformation potentials in $⟨111⟩$ Si NWs. The sudden changes in effective mass and deformation potentials are concurrent with a change in the conduction and valence band edge states. In $⟨110⟩$ NWs, this change corresponds to a transition from direct-to-indirect band gap under strain.

Charge carrier mobility in quasi-one-dimensional systems: Application to a guanine stack

Abstract: First the correct expression of charge mobilities in the one-dimensional (1-D) case in the deformation potential approximation are derived in detail. They differ substantially from the usual 3-D expressions. Starting from an ab initio HF band structure of a guanine stack, the effective masses, the deformation potentials, and the 1-D electron and hole mobilities, respectively, were calculated. The mobility values obtained seem to bee quite reasonable. No attempt was made to calculate from the mobilities the conductivities because of the lack of reliable experimental data (the activation energies of the electron and hole conductivities and dopant concentrations).

Effective-mass theory for InAs/GaAs strained coupled quantum dots

Abstract: In the framework of effective-mass envelope-function theory, the optical transitions of InAs/GaAs strained coupled quantum dots grown on GaAs (100) oriented substrates are studied. At the Gamma point, the electron and hole energy levels, the distribution of electron and hole wave functions along the growth and parallel directions, the optical transition-matrix elements, the exciton states, and absorption spectra are calculated. In calculations, the effects due to the different effective masses of electrons and holes in different materials are included. Our theoretical results are in good agreement with the available experimental data.

Heavy-ion collision theory with momentum-dependent interactions.

Abstract: We examine the influence of momentum-dependent interactions on the momentum flow in 400 MeV/nucleon heavy ion collisions. Choosing the strength of the momentum dependence to produce an effective mass ${m}^{\mathrm{*}}$=0.7m at the Fermi surface, we find that the characteristics of a stiff equation of state can be obtained with a much softer compressibility.