Question

In: Physics

What is the effective mass? How is this different from true mass?

What is the effective mass? How is this different from true mass?

Solutions

Expert Solution

In solid state physics, a particle's effective mass (often denoted m*) is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting thermal distribution. One of the results from the band theory of solids is that the movement of particles in a periodic potential, over long distances larger than the lattice spacing, can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. For some purposes and some materials, the effective mass can be considered to be a simple constant of a material. In general, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors.

For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermionmaterials, or anywhere from zero to infinity (depending on definition) in graphene. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.


Related Solutions

How is the effective mass related to the electron dispersion relation? What is electron dispersion relation...
How is the effective mass related to the electron dispersion relation? What is electron dispersion relation for the valence band and the conduction band of a 1 dimensional semiconductor.
1. From the physics point of view, how 'weight' is different from 'mass' ? Give two...
1. From the physics point of view, how 'weight' is different from 'mass' ? Give two examples of how weight depends on the environment. 2. The force of gravity on a baby elephant near the Earth’s surface is 260 lb (the elephant is about RE = 6371 km from the Earth’s center). What will be the elephant’s weight if the elephant is moved twice as far from the Earth’s center?
What is the importance of calculating the effective stress in a soil mass?
What is the importance of calculating the effective stress in a soil mass?
Case study: Deciding what is effective from different perspectives The aim of this case study is...
Case study: Deciding what is effective from different perspectives The aim of this case study is to illustrate the sometimes competing demands of effectiveness, efficiency and equity. In particular, it should help you to: Explain what is meant by key terms such as ‘LYG’, ‘QALY’ and ‘ICER’ Use these terms and the information they represent in a decision-making scenario ?        Compare and contrast the demands of effectiveness from different perspectives Scenario You are a member of an area prescribing...
How is electronic training (ET) different from e-learning? How effective is ET in maintaining control over...
How is electronic training (ET) different from e-learning? How effective is ET in maintaining control over learning process and training content? Provide your rationale.
What is IRR and how is different from NPV?
What is IRR and how is different from NPV?
What is IRR and how is different from NPV?
What is IRR and how is different from NPV?
Describe how true organs (leaves, stems and roots) are different from structures with similar functions in...
Describe how true organs (leaves, stems and roots) are different from structures with similar functions in nonvascular plants. Also explain, in general (specific differences not needed), how a botanist can tell the difference between the three types of true organs.
What is Care Management and how is it different from CaseManagement?
What is Care Management and how is it different from Case Management?
What is development. How is it different from growth and maturation.
What is development. How is it different from growth and maturation.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT