# What is Fermi surface: Definition and 30 Discussions

In condensed matter physics, the Fermi surface is the surface in reciprocal space which separates occupied from unoccupied electron states at zero temperature. The shape of the Fermi surface is derived from the periodicity and symmetry of the crystalline lattice and from the occupation of electronic energy bands. The existence of a Fermi surface is a direct consequence of the Pauli exclusion principle, which allows a maximum of one electron per quantum state.

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1. ### I About global inertial frame in GR - revisited

Hi, reading this old thread I'd like a clarification about the following: Fermi Normal hypersurface at an event on a comoving FLRW worldline is defined by the collection of spacetime orthogonal geodesics. Such geodesics should be spacelike since they are orthogonal to the timelike comoving...

3. ### Solid-state Physics: Fermi surface and necks in an FCC structure

Does anyone have some bibliography about necks in FCC structure Fermi surface? I have to solve this problem and I have no idea how to start. Thanks.
4. ### A Fermi surface and electronic correlations

why an increase of fermi pockets leads to a reduction of electronic correlations
5. ### A Carving up the Fermi surface

I would like to know every bit of information one can retrieve by looking at the Fermi surface of a material. Here's what I think is correct thus far: 1) The fact that the material has a Fermi surface already tells us a lot. The material could be a metal or something that resembles a metal...
6. ### Solid State Physics: Draw the Dispersion Relation from the Fermi Surface

Homework Statement ln the figure below you (b, which is taken from Jenö Sólyom Fundamentals of the physics of solids. Volume 2 chapter 19) see the Fermi sphere of radius k_F inside one section in two dimensions of the Brillouin zone of Na. Draw the dispersion relation E(k) from the I point in...
7. ### I Fe Lattice: Band Structure & Fermi Surface Location

This is schematic band structure for the dxz and dyz orbitals using a 2D square Fe lattice. What is the location in the Brillouin zone of the hole-like Fermi surface and the electron-like Fermi surface?
8. ### I Hydrostatic Pressure and Fermi Surface

How exactly does hydrostatic pressure affect the shape and size of each Fermi surface in Figure 4B? How do you read this figure or what exactly is it showing?
9. ### A Predicting Fermi Surface from Chemical Formula

Hi, I was hoping I could get some things cleared up. Recently my Solid State professor mentioned that we could simply, from the chemical formula, predict where the band crossings are going to be. For example, take LaFeAsO. Since La has a valency of +3, Fe of +3, As of -3, and O of -2, he...
10. ### I The Mystery of the Fermi Surface & Semiconductors

My teacher told me the other day that a semiconductor does not have a fermi surface. I didn't understand this remark. As I understand it the Fermi Surface is just the surface in k-space spanned by the highest occupied energy levels. Surely in a semiconductor you will also have some highest...
11. ### I Fermi surface spectroscopy

I am reading about angle-resovled-photoemission-spectroscopy (ARPES). It seems that it is a technique that gives the energy dispersion as a function of the momentum k. However in all talks about it, it seems to be a technique that gives us the fermi surface of the given structure. I don't...
12. ### Importance of Fermi Surface in Cooper Pair Formation

Hello, This problem is about cooper pair formation and what happens with the calculations if there is an attractive potential between electrons but it is not in the presence of a filled fermi surface. 1. Homework Statement Two electrons just above the filled Fermi Surface of a material can...
13. ### What are Friedel oscillations and how are they caused?

Hi, and thank you to anyone who replies. I was hoping that someone could please elucidate as to what Friedel oscillations are and what causes them. All of the material that I can find on it is either too simple ("it's an oscillation in the charge density..." or "quantum mechanical analog of...
14. ### Where are the electrons near Fermi Surface spatially distributed in HTS

Namely, are the wave functions of electrons near the Fermi surface spatially distributed in the so-called "active blocks" (CuO2 layers and etc.) or in the so-called "charge reservoir blocks" ? Or any other case? ( EO/(AOx)m/EO with m =1, 2 monolayers of a quite arbitrary oxide AOx(A = Bi, Pb...
15. ### Instability of a 1D material due to Fermi surface nesting

Consider the Lindhard response function: \chi(\vec{q})=\int\frac{d\vec{k}}{(2\pi)^d}\frac{f_\vec{k}-f_{\vec{k}+\vec{q}}}{\epsilon_\vec{k}-\epsilon_{\vec{k}+\vec{q}}} where ##\vec{q}## is the wavevector, ##\epsilon## is the free electron energy and ##f## is Fermi-Dirac distribution function. For...
16. ### Fermi Surface squashed by potentials

Taken from my textbook: My understanding is that: One valence electron, 2 spin states -> Half-filled Brillouin zone Seeking inspiration from "Nearly Free Electron Model": gaps open up at zone boundaries States nearer to zone boundaries get pushed down in energy further Since a fermi...
17. ### Simple (?) question regarding the Fermi Surface

We all see diagrams of the Fermi surface, the representation of the occupied states, but I can't seem to find a precise diagram of when an electric field is applied. Most diagrams show that the surface has moved, BUT they do not say in which direction relative to the electric field, and when...
18. ### Fermi Surface and Orthogonality Catastrophe

I am reading section 8.5.1 of http://f3.tiera.ru/2/P_Physics/PS_Solid%20state/Giuliani%20G.,%20Vignale%20G.%20Quantum%20theory%20of%20the%20electron%20liquid%20%28CUP,%202005%29%28ISBN%200521821126%29%28799s%29_PS_.pdf [Broken] (page 442 of the book, page 465 of the pdf). The author claims the...
19. ### Interpretation to ARPES measured Fermi surface

For any system, different experimental tools are able to measure the Fermi surface or electron dispersion. Then, are these Fermi surface or dispersion the ultimate outcome of the combined effects from the existing interactions? In other words, should the detected motion of electrons have been...
20. ### Tight binding fermi surface

On the attached file the tight binding dispersion for a 2d square lattice is described. It is then assumed that the fermi surface is a square. My question is: How can it ever be a perfect square when the dispersion looks as it does. Also can someone explain: Why does the half filled case...
21. ### Is the Fermi Surface Relevant for Metals with Band Structure?

Does this construction even make sense? By definition it is a surface of constant energy in k-space, so for the free electron it is a sphere. But for metals you have band structure so that a given k-vector can have several different energies associated with it. Which of these are to be chosen?
22. ### Solid state physics fermi surface

Homework Statement Some atoms in Cu crystal (Cu has a FCC lattice) are replaced by Zn atoms. Taking into account that Zn is bivalent, while Cu is monovalent, calculate the atomic ratio of Zn to Cu in ZnCu alloy at which the Fermi surface touches the first Brillouin zone faces. Use the...
23. ### What's the difference between a Luttinger surface and a Fermi surface?

I'm trying to learn about Luttinger's sum rule, but I haven't taken QM yet, and the papers on the topic are very difficult to understand without it. However it seems qualitatively like the Luttinger surface is equivalent to the Fermi surface. If this is not the case, what's the difference? Does...
24. ### Band structure and fermi surface of copper

Hi I've been searching on the web for this two topics, band structure and fermi surface, both of copper. I can't find any of them from a free source, I am doing just a report of my class of introduction to solid state and I just have found this two things in articles that must be bought. If...
25. ### Numbers of electrons on the Fermi surface

In free electron 3D box model, we can calculate the density of state on the Fermi surface g(\epsilonf) easily, but how about the level spacing near the Fermi surface? I think this level spacing \DeltaE should satisfy \DeltaE=d/g(\epsilonf) where d is the degree of degenerate on the Fermi...
26. ### Instability of Fermi surface

Hi Can somebody explain the meaning of the following sentence which is from Wikipedia: "Solids with a large density of states at the Fermi level become unstable at low temperatures and tend to form ground states where the condensation energy comes from opening a gap at the Fermi surface e.g...
27. ### Fermi Surface & Band Diagram Relationship?

Can anyone help explain how one can apply information say from an energy band diagram of an element/compound to its respective fermi surface / "sphere"? I understand there is a direct relationship, however, I can seem to physical interpret how one is able to say look at the energy band...
28. ### Solid State: Fermi surface

Homework Statement Hi all I can't seem to figure out, why semicodunctors do not have Fermi surfaces. At T=0K, there are no electrons in the conduction band, and thus there is no Fermi surface - all OK here. But at T > 0K, there are electrons in the conduction band. Why is it then that it...
29. ### Fermi Surface Topology - U. of Florida

This site has compiled the topology of fermi surfaces for a lot of material. http://www.phys.ufl.edu/fermisurface/ The Science website and the contact e-mail at the end indicate that the people who are responsible for this are at Ohio State (Gokul, do you know any of them?), but it is...
30. ### Fermi Surface Nesting: Explained

What is fermi surface nesting? I don't have a hard reference, but I've heard this term thrown around quite a bit lately when talking about SDW, CDW, and SC.