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.

Extremely slow Drude relaxation of correlated electrons.

Abstract: The electrical conduction of metals is governed by how freely mobile electrons can move throughout the material This movement is hampered by scattering with other electrons, as well as with impurities or thermal excitations (phonons) Experimentally, the scattering processes of single electrons are not observed, but rather the overall response of all mobile charge carriers within a sample The ensemble dynamics can be described by the relaxation rates, which express how fast the system approaches equilibrium after an external perturbation1,2,3 Here we measure the frequency-dependent microwave conductivity of the heavy-fermion metal UPd2Al3 (ref 4), finding that it is accurately described by the prediction for a single relaxation rate (the so-called Drude response5) This is notable, as UPd2Al3 has strong interactions among the electrons4 that might be expected to lead to more complex behaviour Furthermore, the relaxation rate of just a few gigahertz is extremely low—this is several orders of magnitude below those of conventional metals (which are typically around 10 THz), and at least one order of magnitude lower than previous estimates for comparable metals These observations are directly related to the high effective mass of the charge carriers in this material and reveal the dynamics of interacting electrons

Establishing the Golden Range of Seebeck Coefficient for Maximizing Thermoelectric Performance.

Abstract: The coupling nature of thermoelectric properties determines that optimizing the Fermi level is the priority to achieve a net increase in thermoelectric performance. Conventionally, the carrier concentration is used as the reflection of the Fermi level in the band structure. However, carrier concentration strongly depends upon the material’s effective mass, leading to that the optimal carrier concentration varies over a large scale for different materials. Herein, inspired by the big data survey, we develop a golden Seebeck coefficient range of 202–230 μV K–1 for thermoelectric semiconductors with lattice thermal conductivity of 0.4–1.5 W m–1 K–1. When the measured Seebeck coefficient reaches this range, the corresponding figure of merit is maximized. Using this approach, we exemplarily analyze the characteristics of n-type Pb1–xBixSe thermoelectric materials. With detailed electron microscopy and property characterizations, the high densities of dislocations and pores are found to be responsible for a low...

Effective mass in quantum effects of radiation pressure

Abstract: We study the quantum effects of radiation pressure in a high-finesse cavity with a mirror coated on a mechanical resonator. We show that the optomechanical coupling can be described by an effective susceptibility which takes into account every acoustic modes of the resonator and their coupling to the light. At low frequency this effective response is similar to a harmonic response with an effective mass smaller than the total mass of the mirror. For a plano-convex resonator the effective mass is related to the light spot size and becomes very small for small optical waists, thus enhancing the quantum effects of optomechanical coupling.

Effective-mass model and magneto-optical properties in hybrid perovskites

Abstract: Hybrid inorganic-organic perovskites have proven to be a revolutionary material for low-cost photovoltaic applications. They also exhibit many other interesting properties, including giant Rashba splitting, large-radius Wannier excitons and novel magneto-optical effects. Understanding these properties as well as the detailed mechanism of photovoltaics requires a reliable and accessible electronic structure, on which models of transport, excitonic and magneto-optical properties can be efficiently developed. Here we construct an effective-mass model for the hybrid perovskites based on the group theory, experiment and first-principles calculations. Using this model, we relate the Rashba splitting with the inversion-asymmetry parameter in the tetragonal perovskites, evaluate anisotropic g-factors for both conduction and valence bands and elucidate the magnetic-field effect on photoluminescence and its dependence on the intensity of photoexcitation. The diamagnetic effect of exciton is calculated for an arbitrarily strong magnetic field. The pronounced excitonic peak emerged at intermediate magnetic fields in cyclotron resonance is assigned to the 3D±2 states, whose splitting can be used to estimate the difference in the effective masses of electron and hole.

Droplet Model of the Giant Dipole Resonance

Abstract: The nuclear giant dipole resonance is discussed using a macroscopic model with two new features. The motion is treated as a combination of the usual Goldhaber-Teller displacement mode and the Steinwedel-Jensen acoustic mode, and the restoring forces are all calculated using the droplet model. The A dependence of the resonance energies is well reproduced without any adjustable parameters, and the actual magnitude of the energies serves to fix the value of the effective mass m* used in the theory. The giant dipole resonance is found to contain a large component of the Goldhaber-Teller type of motion, with the Steinwedel-Jensen mode becoming comparable for heavy nuclei. The width GAMMA of the giant dipole resonance is estimated on the basis of an expression for one-body damping.