Effective Mass (solid-state Physics)
In solid state physics, a particle's effective mass is the mass it seems to carry in the semiclassical model of transport in a crystal. It can be shown that electrons and holes in a crystal respond to electric and magnetic fields almost as if they were particles with a mass dependence in their direction of travel, an effective mass tensor. In a simplified picture that ignores crystal anisotropies, they behave as free particles in a vacuum, but with a different mass. This mass is usually stated in units of the ordinary mass of an electron me (9.11×10 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher, for example reaching 1000 in exotic heavy fermion materials, and reaching 0 at the so-called Dirac points in graphene.
The effective mass has important effects on the properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.
Read more about Effective Mass (solid-state Physics): Definition, Derivation, Effective Mass For Some Common Semiconductors, Experimental Determination, Significance
Famous quotes containing the words effective and/or mass:
“Justice in the hands of the powerful is merely a governing system like any other. Why call it justice? Let us rather call it injustice, but of a sly effective order, based entirely on cruel knowledge of the resistance of the weak, their capacity for pain, humiliation and misery. Injustice sustained at the exact degree of necessary tension to turn the cogs of the huge machine-for- the-making-of-rich-men, without bursting the boiler.”
—Georges Bernanos (1888–1948)
“For half a mile from the shore it was one mass of white breakers, which, with the wind, made such a din that we could hardly hear ourselves speak.... This was the stormiest sea that we witnessed,—more tumultuous, my companion affirmed, than the rapids of Niagara, and, of course, on a far greater scale. It was the ocean in a gale, a clear, cold day, with only one sail in sight, which labored much, as if it were anxiously seeking a harbor.... It was the roaring sea, thalassa exeessa.”
—Henry David Thoreau (1817–1862)