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.

New Approach to the Renormalization Group

Abstract: A new set of renormalization-group equations is presented. These equations are based on a renormalization procedure in which counterterms are calculated for zero unrenormalized mass. Unlike the Gell-Mann-Low and Callan-Symanzik equations, they can be solved for arbitrary momenta. The solutions involve a momentum-dependent effective mass as well as a momentum-dependent effective coupling constant. By studying these solutions at large momenta, it can be shown that the nonleading terms discarded by previous authors do, in fact, remain negligible when the perturbation series is summed to all orders if, and only if, the effective mass vanishes at large momentum, which will be the case if a certain anomalous dimension is less than unity, as it is in asymptotically free theories. In this case, the new renormalization-group equations can be used at large momentum to derive not only the leading term, but the first three terms in an asymptotic expansion of any Green's function. These results are also applied to Wilson coefficient functions, and an important cancellation of anomalous dimensions is noted.

Bosonic Condensation and Disorder-Induced Localization in a Flat Band

Abstract: We report on the engineering of a nondispersive (flat) energy band in a geometrically frustrated lattice of micropillar optical cavities. By taking advantage of the non-Hermitian nature of our system, we achieve bosonic condensation of exciton polaritons into the flat band. Because of the infinite effective mass in such a band, the condensate is highly sensitive to disorder and fragments into localized modes reflecting the elementary eigenstates produced by geometric frustration. This realization offers a novel approach to studying coherent phases of light and matter under the controlled interplay of frustration, interactions, and dissipation.

Electromagnetic fields and dielectric response in empirical tight-binding theory.

Abstract: Relativistic and nonrelativistic empirical tight-binding theory is generalized to incorporate time-dependent electromagnetic fields in a gauge-invariant manner that does not introduce any extra adjustable parameters. Based on this approach, it is shown that explicit expressions can be derived for the effective mass tensor, the effective Land\'e g factor, the current, the frequency-dependent transverse dielectric function, and the wave-vector- and frequency-dependent longitudinal dielectric function. A finite basis analogue of the optical f-sum rule is derived and shown to impose a condition on tight-binding parameters.

Solutions of the nonrelativistic wave equation with position-dependent effective mass

Abstract: Given a spatially dependent mass distribution, we obtain potential functions for exactly solvable nonrelativistic problems. The energy spectrum of the bound states and their wave functions are written down explicitly. This is accomplished by mapping the wave equation for these systems into well-known exactly solvable Schrodinger equations with constant mass using point canonical transformation. The Oscillator, Coulomb, and Morse class of potentials are considered.

Effective masses of holes at GaAs-AlGaAs heterojunctions.

Abstract: The spin-split hole subband structure is calculated. From it, cyclotron masses as a function of magnetic field are extracted. Agreement with experiment is not good. We argue that many-body effects are important.