In the 80s, in our electronics classes in semiconductor or solid state physics, such as semiconductor diodes, LEDs, transistors, integrated circuits, BJTs, thyristors, triacs, fets, mosfets and many more, we learned the effective mass of electrons, a very interesting topic, which I'm sharing now.
Electron effective mass (mₑ*) is a concept in solid-state and semiconductor physics that describes the behavior of electrons in a crystal lattice or semiconductor material. In these materials, electrons experience periodic potentials, causing them to behave differently based on their momentum and the crystal's band structure. Effective mass is the modified mass of electrons, which can vary in different crystal directions. It is determined experimentally or theoretically from the element's electronic band structure. In some cases, the effective mass of electrons in a semiconductor can be negative, causing unusual phenomena like negative differential resistance.
It is important to note that the electron rest mass (mₑ) is a fundamental constant and is always the same for electrons, regardless of the material in which they reside. On the other hand, electron effective mass (mₑ*) is a material-dependent property that describes how electrons behave in certain materials under certain conditions.
