Condensed matter Definition and 168 Threads

Everytime that I deal with Bogoliubov transformations I get some sign wrong or a missing assumption. Let's take the case for fermions $$c_{\mathbf p \sigma}=u_{\mathbf p \sigma} b_{\mathbf p \sigma} +v_{\mathbf p \sigma} b^\dagger_{-\mathbf p \bar{\sigma}}$$ where ##\sigma## is the spin...

If you have many free electrons forming a cloud they wouldn't last too much as they would be repelled from each other due to electromagnetic forces. Gravity wouldn't help since it is much weaker than electromagnetic force, so electrons would still fly away However, can they be stabililized by...

Imagine we have a cold region of the universe, almost devoid of matter and radiation. Or perhaps in a future universe where the CMB has "cooled" down to sufficiently low "temperatures" Could there be long lived macroscopic Bose-Einstein and Fermionic states of matter there? Could matter...

TL;DR Summary: I am asking for how to study CMT Any advice in connecting concepts and building intuition for condensed matter? Sometimes I can do some problems operationally, but I can't see connection between different problems and doesn't have a mental model or intuition? I can think of read...

I got confused by the band theory. Does the band gap imply the voltage needed to conduct? This seems to be ridiculous. The band gap of a typical insulator is on the order of a few eV. Hence, if you give electrons 10 eV, they jump to the conduction band. But surely you can't turn an insulator...

Hi Pholks, I just change my field of study from cosmology to condensed matter and I have a severe lack of knowledge in condensed matter. Having only some concepts in quantum mechanics and field theory, I would like to ask if there are anyone who wants to setup a weekly study group to discuss...

Honestly, I have no real idea. I know for sure the equation connects the initial state ##|\Psi^N_0>##to a final state ##|\Psi^{N+1}_0>##, ##E## is the energy and ##E^N_0## etc are the energy of the initial state and final state. I also know that these energy are related to conduction band and...

I am trying to understand Green's functions in many-body theory for condensed matter. After much struggle, I managed to calculate my first diagrammatic expansion. However I am perplexed by getting more of the usual results. The Hartree–Fock energy result I know from second quantization can be...

Crystals may contain electronic real-space-eigenstates as ground states, which are spatially much larger than one unit cell, such as impurity states, standing waves at Brillouin zone edges, states of Anderson localization, etc. Every eigenstate is usually occupied by two conduction electrons...

Hey all, I was just wondering where I could find a current review of the major problems that are being discussed at the intersection of condensed matter theory and high energy theory (+maybe quantum information)? Just looking for some inspiration on what the most "popular" problems being...

This question is more complicated than it seems, most physicists cannot answer it unambiguously and there is no experiments to the issue. Imagine, a persistent supercurrent flows in a SC aluminum ring. Then we connect the SC aluminum ring (without solder) to an aluminum wire, the second end of...

The model that he uses is a dielectric in which there is a spherical cavity with a dipole at its center. The dipole ##\vec{m}## has a component due to a permanent dipole and a component due to an induced dipole (because of polarization). In order to obtain the dipole moment in the cavity, the...

What is the A x B labeling referring to when discussing charge density waves? For example the 2x2 CDW structure in TiTe2 (link). Is it I have searched through a fair amount of literature (from Grüner to more recent experimental studies) and it doesn't seem to be explained anywhere that I've...

I was wondering if anyone knows of any technical pop-sci books about condensed matter physics and/or superconductivity that are at the technical level of something like the "A Very Short Introduction" series or the Feynman lectures. That is, something that goes sufficiently into depth into the...

What is meant when a phase is said to have "symmetry protected"?

Hello, I was not sure whether this should belong to this section or the condensed matter section. I am wondering if after about 15 years in research in topological condensed matter, there exist well-recognized references for beginners in the topic. Books or courses but also review articles...

I have made solutions a-d, but my fermi velocity seems too big.

Imagine, in a mercury ring (superconductivity below Tc=4.15 K) we establish a persistent supercurrent. Then we organize temperature cycles (T-cycles) in the cryostat, from 3 K to 2.5 K and back. According to the BCS theory of superconductivity, the pair density decreases at warming, i.e. a not...

Can you please recommend me some condensed matter physics study books and semi-conductor physics study books? Much Appreciated!

Do they really teach and help anything? I am taking them for my nanoengineering undergraduate program. The textbooks are solid state physics by j r hook and concepts of modern physics by mcgraw hill and r b singh introduction to modern physics and introduction to quantum mechanics by david j...

I know in RVB theory that neighbouring Copper atoms form singlet pairs via the superexchange "force". Upon doping with holes, these neutral singlet RVB pairs become mobile and charged and are able to superconduct. I know that the resonating valence bonds are in the copper 3d(x^2-y^2) orbital and...

Hi all, I just graduated from my master's program in theoretical physics. I did 60% of the coursework in high energy physics and rest in condensed matter theory plus a few experimental physics courses. I did my master's thesis in what can be called as theoretical cosmology, studying particle...

I am on my first year of my master's degree in nuclear and particle physics, and right now i am ending my first semester, where i decided to take a course in physics of semiconductors. As i end this semester i start to wonder if there was any use in learning about this subject, as it seems like...

We have a one dimensional lattice with a lattice constant equal to a (I'm omitting vector notation because we are in 1D). The reciprocal lattice vector is k_n=n\frac{2 \pi}{a}. So to get the nearest neighbour approximation I need to sum over k = -\frac{2 \pi}{a}, 0, \frac{2 \pi}{a}. If I...

Consider a PN junction doped with say phosphorous on the N side, and Boron on the P side. Initially, there is an opportunity for the electrons just below the N conduction band to drop to the lower available energy states just above the P valence band. This leaves the N side positively charged...

Hi, I want to measure spin components of a ground state of some models. These ground states are obtained by ED. The states for constructing the Hamiltonian are integers representing spins in binary. As the ground state (and the other eigenvectors) are now not anymore in a suitable representation...

I am trying to understand how is topology used to characterize materials. So I understand that to calculate the Berry phase you will parameterize your Hamiltonian and change this parameter in some way and return to the initial value. What I do not understand is what does this changing of...

I am struggling to understand shocks in a one dimensional lattice with a linear spring connecting the masses. Say I have a one dimensional lattice with a linear spring constant, k and lattice spacing a. If the particles in the lattice has mass, m then my speed of sound c is a*sqrt(k/m). That is...

Summary:: What is the advantage of transparent semiconductors such as Fluorine doped tin oxide over main semiconductors? What is the advantage of transparent semiconductors such as Fluorine doped tin oxide (FTO) and Indium tin oxide (ITO) over main semiconductors? Please explain the uses of...

Hi, I don't want to be too specific here, but specific enough for relevant advice. I'm finishing a Masters in Physics and am lucky to have been made offers by 2 excellent institutes: a Max Planck Graduate Centre (MP), and at Oxford UK. Both are in experimental condensed matter; Weyl...

My name is Irene and I've just started my PhD. at the University of Barcelona (October, 2020). I have a Physics degree and a Master in Computational Modelling. I work in a research group named ClabB (complexity lab Barcelona) where I develop a large scale opinion model using Monte-Carlo...

This is going to be controversial and might even be taken down, but I think what I will say is absolutely true, and I'm sorry if it offends people. I'm applying for the second time to condensed matter PhDs. I was in a group that did a lot of device fabrication as part of their experiments and...

I have my MSc in 'Computational condensed matter physics'. I used VASP package for simulation during my MSc. and i am also well experienced in FORTRAN programming language. Can anyone give me short note about 'PhD in computational physics'? so that can continue my PhD in 'Computational Physics'.

Assuming the electrons are non interacting and spin degenerate, the conductance of a quasi one dimensional quantum wire is quantised in units of 2e^2/h. For small voltages, we simply count how many bands have their bottoms below the chemical potential and multiply this by 2e^2/h. This is due to...

What books are recommended for a course in condensed matter physics at a graduate level?

I'm working on a PhD in condensed matter computational physics, particularly with method development. My plan is to go into industry afterwards, and out of curiosity I've been looking at job listings. It doesn't look good to be honest. Listings for physicists mainly require some type of lab...

Hey guys. I have offers to do summer research at both Brown University and University of Chicago this summer, and I was wondering which school has a stronger department in regards to condensed matter theory. Personally, I think it's University of Chicago, but I'm not too sure and I'd appreciate...

In your opinion, what are the main challenges for future condensed matter physics? What type of material systems are more desirable to discover? Which quantum properties are the most interesting to demonstrate for future devices working at room temperature and ambient pressure (besides...

Well, I don't understand the integral part of ##1/(VD) = \int_0^{\hbar \omega_D}\frac{\tanh(\beta E/2}{E}dE## and ##\tanh(\beta E/2) \approx 1-2\exp(-\beta E)##, then he writes the following (which I don't understand how did he get it): $$\frac{1}{VD} = \sinh^{-1} (\hbar \omega/\Delta(0)) =...

Title? Thanks. I think it does since these do : - Quasi particles - Collective behaviour of particles - Phase transitions Any others?

What kind of research is currently going on in the field of quantum spin liquids and why do we study spin liquids?

I am torn between computational and experimental condensed matter physics for my PhD. My focus is on low dimensional systems (e.g. electron correlation/transport, broken symmetry at the boundaries). I'm currently in the process of applying for graduate schools, and so far, I've chosen all my...

So far the best I've been able to come up with is to use ##\vec{B} = \mu_0 \vec{H}## which gives me i_c = H 2\pi r j_c = \frac{H 2\pi r}{\pi r^2} = \frac{2H}{r} \therefore B = \mu_0 \frac{r j_c}{2} I'm fairly confident this is just terrible math and physics on my behalf but I'm struggling to...

Dear all, in the context of my teaching I was wondering what exactly the explanation is of how a mirror works at the atomic level. Apparently, the fact that reflecting materials are often also good conductors and hence big energy bands helps reflecting the photons. Does someone know a nice set...

For my own understanding, I am trying to computationally solve a simple spinless fermionic Hamiltonian in Quantum Canonical Ensemble formalism . The Hamiltonian is written in the second quantization as $$H = \sum_{i=1}^L c_{i+1}^\dagger c_i + h.c.$$ In the canonical formalism, the density...

Hello everyone, I'm a Physics student on a gap year, doing a bit of work ATM. I'm going to come back in October this year to do a one-year Masters' at Cambridge, and I'm faced with a tough choice: A) Specialize in Astrophysics/cosmology, which is something that I'm not as good at, but really...

I am trying to understand Aubry-Andre model. It has the following form $$H=∑_n c^†_nc_{n+1}+H.C.+V∑_n cos(2πβn)c^†_nc_n$$ This reference (at the 3rd page) says that if ##\beta## is irrational (rational) then the period of potential is quasi-periodic incommensurate (periodic commensurate) with...

I'm a physics and math major, going into my 3rd year. Suppose I want to do research in theoretical aspects of condensed matter. What would be the mathematics I should be learning as an undergraduate? Here is a rundown of courses I'm considering taking next year: Abstract Algebra: it seems a...

How can I see, by looking at a band structure if the substance in question can be viewed as a free electron gas (FEG) or not? What characterizes a FEG in a bandstructure plot? Thanks in advance!

Hello, I am currently struggling to understand how one can write a Hamiltonian using group theory and change its form according to the symmetry of the system that is considered. The main issue is of course that I have no real experience in using group theory. So to make my question a bit less...