Related Concept Videos
01:21Joule-Thomson Effect
The Joule-Thomson effect, also known as the Joule-Kelvin effect, describes the temperature change of a fluid when it is forced through a valve or porous plug while keeping it in a thermally insulated environment. This experiment is called a throttling process. This is an important effect widely used in refrigeration and the liquefaction of gases.
This experiment forces high-pressure gas through a throttle valve or a porous plug to a lower-pressure region. The gas expands as it passes through to...
This experiment forces high-pressure gas through a throttle valve or a porous plug to a lower-pressure region. The gas expands as it passes through to...
01:19Mechanism of heat transfer
Understanding heat transfer mechanisms is essential for understanding how our bodies maintain balance in different environmental conditions. When the environment is thermoneutral, the body is in a state of balance, neither using nor releasing energy to maintain its core temperature. However, when the environment is not thermoneutral, the body employs four heat transfer mechanisms to maintain homeostasis: conduction, convection, evaporation, and radiation. These mechanisms facilitate heat...
01:20Mechanisms of Heat Transfer II
In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the buoyancy of warm air and water, transfer hot air from the tropics toward the poles and cold air from the poles toward the tropics. The Earth’s rotation interacts with those flows, causing the observed eastward flow of air in the temperate zones. Convection dominates heat transfer by air, and the amount of available space for the airflow...
01:21Carrier Transport
The generation of electrical current in semiconductors is fundamentally driven by two mechanisms: drift and diffusion. These processes are essential for the functionality and performance of semiconductor-based devices.
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
02:39Phase Transitions: Vaporization and Condensation
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...
01:14Mechanisms of Heat Transfer I
Just as interesting as the effects of heat transfer on a system are the methods by which the heat transfer occur. Whenever there is a temperature difference, heat transfer occurs. It may occur rapidly, such as through a cooking pan, or slowly, such as through the walls of a picnic ice box. So many processes involve heat transfer that it is hard to imagine a situation where no heat transfer occurs. Yet, every heat transfer takes place by only three methods: conduction, convection, and radiation.
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Related Experiment Video
Updated: May 17, 2026
11:21
Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving
Published on: March 30, 2017
Carrier cooling in colloidal quantum wells.
Matthew Pelton1, Sandrine Ithurria, Richard D Schaller
1Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439, United States. pelton@anl.gov
Nano Letters
|November 10, 2012
Summary
Chemically synthesized semiconductor nanoplatelets exhibit quantum-well properties, confirmed by carrier relaxation studies. Their rapid cooling suggests suitability for optoelectronic devices like lasers and modulators.
Area of Science:
- Materials Science
- Nanotechnology
- Quantum Physics
Background:
- Atomically flat semiconductor nanoplatelets with precise thickness control are now synthesizable.
- These nanoplatelets are hypothesized to function as quantum wells, confining carriers in one dimension.
Purpose of the Study:
- To experimentally confirm the quantum-well nature of semiconductor nanoplatelets.
- To investigate carrier relaxation dynamics in these nanomaterials.
Main Methods:
- Time-resolved photoluminescence spectroscopy.
- Transient-absorption spectroscopy to study carrier relaxation.
Main Results:
- Experimental evidence confirms the quantum-well behavior of the semiconductor nanoplatelets.
- Observation of a high-temperature carrier population cooling to ambient temperature within picoseconds.
Conclusions:
- The semiconductor nanoplatelets behave as quantum wells.
- Rapid carrier cooling indicates significant potential for optoelectronic applications, including lasers and modulators.