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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.


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Journal ArticleDOI
TL;DR: It is shown that a secondary conduction band with 12 conducting carrier pockets (which converges with the primary band at high temperatures) is responsible for the extraordinary thermoelectric performance of n-type CoSb3 skutterudites.
Abstract: Filled skutterudites R_xCo_4Sb_(12) are excellent n-type thermoelectric materials owing to their high electronic mobility and high effective mass, combined with low thermal conductivity associated with the addition of filler atoms into the void site. The favourable electronic band structure in n-type CoSb3 is typically attributed to threefold degeneracy at the conduction band minimum accompanied by linear band behaviour at higher carrier concentrations, which is thought to be related to the increase in effective mass as the doping level increases. Using combined experimental and computational studies, we show instead that a secondary conduction band with 12 conducting carrier pockets (which converges with the primary band at high temperatures) is responsible for the extraordinary thermoelectric performance of n-type CoSb_3 skutterudites. A theoretical explanation is also provided as to why the linear (or Kane-type) band feature is not beneficial for thermoelectrics.

555 citations

Journal ArticleDOI
TL;DR: In this article, a simple expression for the low field mobility in the miniband conduction regime is derived; localization effects, hopping conduction, and effective mass filtering are discussed.
Abstract: New results on the physics of tunneling in quantum well heterostructures and its device applications are discussed. Following a general review of the field in the Introduction, in the second section resonant tunneling through double barriers is investigated. Recent conflicting interpretations of this effect in terms of a Fabry-Perot mechanism or sequential tunneling are reconciled via an analysis of scattering. It is shown that the ratio of the intrinsic resonance width to the total scattering width (collision broadening) determines which of the two mechanisms controls resonant tunneling. The role of symmetry is quantitatively analyzed and two recently proposed resonant tunneling transistor structures are discussed. The third section deals with perpendicular transport in superlattices. A simple expression for the low field mobility in the miniband conduction regime is derived; localization effects, hopping conduction, and effective mass filtering are discussed. In the following section, experimental results on tunneling superlattice photoconductors based on effective mass filtering are presented. In the fifth section, negative differential resistance resulting from localization in a high electric field is discussed. In the last section, the observation of sequential resonant tunneling in superlattices is reported. We point out a remarkable analogy between this phenomenon and paramagnetic spin resonance. New tunable infrared semiconductor lasers and wavelength selective detectors based on this effect are discussed.

555 citations

Journal ArticleDOI
TL;DR: In this article, the binding energy of the exciton (R*) and its reduced effective mass (μ) were investigated in the context of perovskite materials, where the excitonic states were fit as a hydrogenic atom in magnetic field and the Landau levels for free carriers to give R* and μ.
Abstract: The family of organic–inorganic halide perovskite materials has generated tremendous interest in the field of photovoltaics due to their high power conversion efficiencies. There has been intensive development of cells based on the archetypal methylammonium (MA) and recently introduced formamidinium (FA) materials, however, there is still considerable controversy over their fundamental electronic properties. Two of the most important parameters are the binding energy of the exciton (R*) and its reduced effective mass μ. Here we present extensive magneto optical studies of Cl assisted grown MAPbI3 as well as MAPbBr3 and the FA based materials FAPbI3 and FAPbBr3. We fit the excitonic states as a hydrogenic atom in magnetic field and the Landau levels for free carriers to give R* and μ. The values of the exciton binding energy are in the range 14–25 meV in the low temperature phase and fall considerably at higher temperatures for the tri-iodides, consistent with free carrier behaviour in all devices made from these materials. Both R* and μ increase approximately proportionally to the band gap, and the mass values, 0.09–0.117m0, are consistent with a simple k.p perturbation approach to the band structure which can be generalized to predict values for the effective mass and binding energy for other members of this perovskite family of materials.

552 citations

Journal ArticleDOI
TL;DR: In this article, the analysis of Fowler-Nordheim tunneling data in metaloxide-silicon structures is reviewed, and it is concluded that a parabolic dispersion relation for SiO2 and an electron effective mass of mox = 0.5m provide the best description of the experimental results.
Abstract: The analysis of Fowler‐Nordheim tunneling data in metal‐oxide‐silicon structures is reviewed. It is concluded that a parabolic dispersion relation for SiO2 and an electron effective mass of mox = 0.5m provide the best description of the experimental results, this conclusion is consistent with recent band structure calculations for SiO2. Also included is a brief discussion of the transverse momentum conservation issue for tunneling from silicon of 〈100〉, 〈110〉, and 〈111〉 orientation into SiO2.

547 citations

Journal ArticleDOI
TL;DR: The first experimental realization of a dispersionless state is demonstrated, in a photonic Lieb lattice formed by an array of optical waveguides, which opens an exciting door towards quantum simulation of flat-band models in a highly controllable environment.
Abstract: We demonstrate the first experimental realization of a dispersionless state, in a photonic Lieb lattice formed by an array of optical waveguides. This engineered lattice supports three energy bands, including a perfectly flat middle band with an infinite effective mass. We analyze, both experimentally and theoretically, the evolution of well-prepared flat-band states, and show their remarkable robustness, even in the presence of disorder. The realization of flat-band states in photonic lattices opens an exciting door towards quantum simulation of flat-band models in a highly controllable environment.

527 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202215
2021410
2020421
2019395
2018362
2017412