# 2-dimensional valley degeneracy

• jarra
In summary, the conversation discusses the need for information on the valley degeneracy of a 2DEG for Si, GaAs, InAs, and Ge. Sources for finding this information are requested and it is mentioned that the measured degeneracy may be lower due to strain fields. A PRL by Dan Tsui is suggested as a helpful resource.
jarra
I was about to do a simulation on www.nanohub.org on a MOSFET when the simulation program asked me for the valley degeneracy of the 2DEG.
I've tried to look this up but i can't find it anywhere.
Does somebody know a website where I can find the valley degeneracy for a 2DEG for Si, GaAs, InAs and Ge?

The theoretical valley degeneracies for GaAs(100?) and Si(111) are respectively 3 (not 100% certain about this) and 6. The typical valley degeneracy measured in experiments, however, is lower due to inhomogeneous strain fields that lift some of the degeneracy. For, Si(111), the most commonly measured value is 2 and for GaAs, I think it is 1.

There's a PRL by Dan Tsui on the first measurement of the 6-fold degeneracy in Si(111). This paper, and its references should get you most of the information you need.

Thank you for the help! I will have a look at the PRL by Dan Tsui.

## 1. What is a "2-dimensional valley degeneracy"?

A "2-dimensional valley degeneracy" refers to a phenomenon in physics where there are multiple energy levels in a 2-dimensional system that have the same energy. This means that there are multiple states or configurations of the system that have the same energy, making it difficult to distinguish between them.

## 2. How does "2-dimensional valley degeneracy" occur?

"2-dimensional valley degeneracy" can occur due to symmetries in the system, such as rotational or reflection symmetries, which result in multiple states having the same energy. It can also occur in materials with anisotropic properties, where the energy levels are different in different directions, but still have degeneracy within those directions.

## 3. What are the implications of "2-dimensional valley degeneracy"?

The presence of "2-dimensional valley degeneracy" can have significant implications in materials science and condensed matter physics. It can affect the electronic and optical properties of materials, as well as their thermal and mechanical properties. It also plays a crucial role in the design and development of electronic devices and technologies.

## 4. How is "2-dimensional valley degeneracy" studied and measured?

Scientists use various experimental techniques, such as angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM), to study and measure "2-dimensional valley degeneracy". These techniques allow them to observe the energy levels and states of the system and determine if there is degeneracy present.

## 5. Can "2-dimensional valley degeneracy" be controlled or manipulated?

Yes, "2-dimensional valley degeneracy" can be controlled and manipulated through various methods such as applying external electric or magnetic fields, or by using different materials and structures. Researchers are actively studying ways to manipulate "2-dimensional valley degeneracy" in order to create new materials with unique properties for potential applications in electronics and other fields.

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