Trying to get a physical understanding of a Fermi gas

In summary, the conversation discusses the concept of conduction electrons in a metal, specifically the fermi gas model. The confusion lies in the first ionization energy and whether the electrons would rather conduct or combine with the ions. The conversation also touches on the quantum states of electrons and the concept of a "box" where the electrons are confined. The correct understanding is that the electrons in a metal are not bound to a single atom, but rather exist in a delocalized state within the solid material.
  • #1
MarkL
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TL;DR Summary
trying to get a physical understanding of fermi gas
I would like to get a more physical interpretation of conduction electrons (fermi gas) in a metal. I imagine ionized valence electrons close to the ions, with the fermi level (highest energy electrons) of the gas participating in conduction. A point of confusion for me...the first ionization energy for most metals are always higher than the fermi level, i.e. wouldn't the electron want to combine with the ions rather than conduct?

Also, I have some confusion with quantum states. Textbooks usually demonstrate this with ##λ_n##'s in a potential well. To understand the actual position of electrons (fermions), I give the well zero potential. This is just a box. At low density this is a classical gas. At higher densities, where the space between electrons is less than DeBroglie wavelength, this would be quantum. By Pauli exclusion, one electron (λ) per well. So, N electrons in N identical states (wells) and identical fermi energies. Is this correct?
 
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  • #2
MarkL said:
A point of confusion for me...the first ionization energy for most metals are always higher than the fermi level, i.e. wouldn't the electron want to combine with the ions rather than conduct?

If I'm not mistaken, the first ionization energy is only for single atoms, not atoms that are bound into the metallic lattice of a bulk material. When bound, the valence states overlap and allow for the delocalization of the electrons occupying those states. So the valence electrons are not bound to a single atom, despite not being ionized.
 
  • #3
MarkL said:
Summary:: trying to get a physical understanding of fermi gas

So, N electrons in N identical states (wells) and identical fermi energies. Is this correct?
If I understand you, this is very wrong. The electrons (particularly conduction electrons) are all in one "box" which is the chunk of solid matter. The different states are quantized because the wavelength must match the box boundary conditions and Fermi exclusion prevails. The Fermi level is where you are in wavenumber when you put in the final electron. This is basic solid state theory a la Ashcroft and Mermin.
 

FAQ: Trying to get a physical understanding of a Fermi gas

What is a Fermi gas?

A Fermi gas is a collection of fermions, which are particles that follow the Pauli exclusion principle and have half-integer spin. Examples of fermions include electrons, protons, and neutrons. In a Fermi gas, these particles are not interacting with each other, but are subject to external forces such as temperature and pressure.

How is a Fermi gas different from a Bose gas?

A Bose gas is a collection of bosons, which are particles that do not follow the Pauli exclusion principle and have integer spin. Unlike fermions, bosons are able to occupy the same quantum state. This leads to different behaviors in a Bose gas compared to a Fermi gas, such as the formation of a Bose-Einstein condensate at low temperatures.

What is the Fermi energy and why is it important?

The Fermi energy is the maximum energy that a fermion in a Fermi gas can have at absolute zero temperature. It is a fundamental property of the system and is related to the number of fermions and the volume of the gas. The Fermi energy is important because it determines the behavior of the gas at low temperatures, such as whether it will undergo a phase transition to a Bose-Einstein condensate.

How does the temperature affect a Fermi gas?

At low temperatures, a Fermi gas will exhibit behavior similar to an ideal gas, with particles moving independently and obeying the laws of classical physics. As the temperature increases, the gas will start to deviate from ideal gas behavior due to quantum effects. At high enough temperatures, the gas may undergo a phase transition to a Bose-Einstein condensate.

What are some real-world applications of studying Fermi gases?

Fermi gases have many applications in fields such as condensed matter physics, nuclear physics, and astrophysics. They can be used to model the behavior of electrons in metals, study the properties of neutron stars, and understand the behavior of matter in extreme conditions. Additionally, studying Fermi gases can also lead to technological advancements, such as the development of new materials with unique properties.

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