Condensed Matter Physics - Science topic

How do you know?

Originally a trial of the second law of thermodynamics, it has become a trial of scientists. I believe there will be a response from scientists.

But why do you expect this to be wrong?

The heterostructure might have a different symmetry with respect to the parents.

Maybe if you look at the projection of the bands on the different atoms, you might discover how forming the heterostructure the atomic contribution changes and how the band moved to the Gamma point.

I hope this helps,

Roberto

Hi Dear Prof. Stanislav Dolgopolov

Thank you for the answer & well it seems to be logical, but you do specify the mechanism implicitly, when you write the statement "the created pairs, which initially didn't participate in the current", because you are saying that new pairs of supercurrent bosons are created somehow. They are created, and there is a superconducting mechanism for their creation, even we do not know which one is, if BCS or another unknown one.

Kind Regards.

Now scientists have enough thermal property data to test the correctness of the second law of thermodynamics, as long as they are willing.

The discontinuity (artificially induced) in the thermophysical properties of substances, such as temperature or pressure, can indeed affect the application of the second law of thermodynamics. The second law states that heat naturally flows from a higher-temperature region to a lower-temperature region, and this principle relies on the continuous and smooth behavior of thermophysical properties.

When discontinuities are introduced, it can lead to non-ideal behavior and deviations from the expected thermodynamic processes. For example, abrupt changes in temperature or pressure could result in unexpected phase transitions or heat transfer behaviors that don't follow the usual laws of thermodynamics.

Therefore, it's essential to maintain the continuity of thermophysical properties to accurately apply the second law of thermodynamics in various engineering and scientific applications. Researchers and engineers often work to minimize or correct such artificial discontinuities to ensure the reliability of thermodynamic calculations and processes

The moment we say reversible, we are already in...

Hey there, my fellow researcher Ze Zhang! It's fantastic that you're exploring the world of hBN. Now, let's talk about determining its direction.

When it comes to identifying the direction of hBN, polarization Raman spectroscopy is indeed a powerful tool in your arsenal. Here's how you can use it:

1. **Polarization-Resolved Raman Spectroscopy**: You can perform Raman spectroscopy on your hBN sample with different incident laser polarizations (typically, parallel and perpendicular to the crystal axis). The Raman intensity of certain vibrational modes will vary depending on the polarization direction. By analyzing these variations, you can determine the orientation of hBN.

2. **Depolarization Ratio**: Calculate the depolarization ratio for specific Raman modes. The depolarization ratio is the ratio of the intensity of scattered light with perpendicular polarization to the intensity of scattered light with parallel polarization. It provides valuable information about the orientation of the crystal.

3. **Orientation Mapping**: If you have a large hBN sample, you can create an orientation map by measuring Raman spectra at multiple points across the sample surface. This will help you visualize the orientation distribution of hBN domains.

Remember to ensure that your experimental setup is aligned correctly for polarization measurements and consult Raman literature for guidance on which vibrational modes are sensitive to polarization.

Feel free to ask if you have more questions or need further assistance with your hBN research. Best of luck with your experiments! 🚀🔬

Air above the equator is heated more and areas near the equator receive more heat from the sun than those near the poles due to a phenomenon called "solar angle" and the way the Earth's curvature and atmosphere interact with incoming solar radiation. This is primarily caused by the Earth's axial tilt and its spherical shape.

1. Solar Angle: The angle at which sunlight reaches a particular location on Earth's surface is a crucial factor. Near the equator, sunlight strikes the surface more directly and perpendicularly compared to regions near the poles. When sunlight strikes a surface at a steeper angle, the same amount of energy is concentrated over a smaller area, leading to higher temperatures. In contrast, at higher latitudes (closer to the poles), sunlight is spread over a larger surface area due to the oblique angle of incidence, resulting in less heating.

2. Earth's Curvature and Atmosphere: The curvature of the Earth plays a role in how sunlight is distributed. Near the equator, the curved surface presents a relatively small area for the sun's energy to be distributed, concentrating the heat. Additionally, the atmosphere plays a significant role in moderating the amount of solar radiation that reaches the surface. When sunlight passes through a thicker layer of atmosphere, it can scatter and be absorbed, reducing the amount of energy that reaches the surface. Near the equator, the sunlight has to pass through a smaller portion of the atmosphere, allowing more energy to reach the surface and result in higher temperatures.

3. Day Length: Near the equator, the length of day and night remains relatively consistent throughout the year. This means that the sun is up for a significant portion of the day, allowing more time for the surface to absorb and store heat. In contrast, areas closer to the poles experience more extreme variations in day length, with long days in the summer and long nights in the winter. This variation affects the amount of time available for solar heating.

4. Heat Redistribution: The equatorial region receives more heat than it radiates back into space, creating a surplus of energy. This excess heat is then transported toward the poles through atmospheric and oceanic circulation patterns, which help to distribute heat around the planet and regulate global climate patterns.

The combination of the solar angle, Earth's curvature, atmospheric effects, and heat redistribution mechanisms results in the equatorial region receiving more direct and concentrated solar energy, leading to higher temperatures compared to areas closer to the poles.

Dear Scien Tist,

The binding energy of your Ba 3d_5/2 peak is way too high with 808 eV. Either someone really messed up the calibration of your system, or, what I think is more likely, your material is not conductive enough and you observe charging. Are the binding energies of other peaks, like O 1s or C 1s, where you would expect them to be?

You should ask scientists why they are not generous enough to use method a and instead use fraudulent method b

Discontinuity (artificially) of The Thermophysical Properties of NIST affects the second law of thermodynamics：

1) Scientists create Type 2 perpetual motion machines;

2) Scientists have discovered new laws of phase transition.

3) Scientists don't need to create a bunch of fake things for the second law of thermodynamics.

Discontinuity (artificially) of The Thermophysical Properties of NIST affects the second law of thermodynamics：

1) Scientists create Type 2 perpetual motion machines;

2) Scientists have discovered new laws of phase transition.

3) Scientists don't need to create a bunch of fake things for the second law of thermodynamics.

the question is not 'failure of second law of thermodynamics' but what triggers convection - even very small temperature gradients are sufficient.

If you have two real gases, the claim dW=0 is incorrect, especially in the differential form, and therefore you will get additional terms in all subsequent equations.

Dear Bo Miao.

You can write anything. Paper will endure everything.

The first law of thermodynamics dU = TdS - pdV is sufficient to understand temperature T as the rate of transfer (flow) of energy, and pressure p as the rate of transfer of momentum from one body in contact to another.

Therefore, you will never, under any circumstances, get a positive value if you subtract a large value from a small value.

Sincerely, Dulin Mikhail.

Dear Dipta Mahanta,

But you cannot do this:

"nbnd: Used 100 (in bands) instead of 544 (which is default) for faster calculation and for testing purpose"

nbnd is the number of bands to be calculated; you might want to increase it, not decrease it. Indeed, it corresponds to the number of states you make available to the electrons in your materials. QE will start allocating the electrons to each band and then probably crash because there are not enough.

Indeed, in your output, you can read

"number of electrons = 640.00

number of Kohn-Sham states= 100"

How can you fit 640 electron in 100 states? The code is going to crash somewhere.

Moreover,

"ecutrho: 400 (scf) to 700 (bands)"

"ecutwfc: 50 (scf) to 100 (bands)"

These two changes do not make much sense. Remember that the quality of the SCF calculation is in the SCF step and parameters. The calculations="bands" is a NON-SCF type of calculation -- it starts by reading the SCF output and builds from there interpolating the missing points. For example, the density, the central piece of information in DFT, in the non-SCF calculation is not changed.

My advise for a band calculation is to copy the SCF input file and then simply change calculation="bands" and the k-point mesh to what you need.

Finally, why do you want to run a band calculation with a supercell? The result ought to be identical to the case with a simpler cell, once you have unfolded the bands. In this respect, the band calculation offers no new insight into the physics of the supercell.

Best regards,

Roberto

Dear Yang Song ,

It is true that in general, the bandgap of compound semiconductors decreases with an increase in average atomic number. Therefore, it is expected that the bandgap of ZnSe (average atomic number of 33.4) should be smaller than CdSe (average atomic number of 52.2). This is because the increase in atomic number leads to a stronger binding energy, which reduces the energy required to excite an electron to the conduction band. However, it is also important to note that the bandgap is not solely determined by the average atomic number but also by other factors such as crystal structure and bond length. In the case of ZnO and ZnS, the difference in bandgap can be attributed to the difference in crystal structure and bond length. The crystal structure of ZnO is hexagonal wurtzite, whereas ZnS has a cubic zincblende structure.The wurtzite crystal structure of ZnO is characterized by a large polarization effect, which leads to the formation of a spontaneous electric field along the c-axis of the crystal. This electric field lowers the energy of the conduction band minimum and increases the energy of the valence band maximum, resulting in a smaller bandgap. In contrast, the zinc-blende crystal structure of ZnS does not exhibit this spontaneous electric field effect. Also, the bond length of Zn-O is longer than Zn-S, which leads to weaker bonding and a smaller bandgap.

Hope this helps!

Regards,

Chris J Benmore ,

It is known that water has unique properties compared to other liquids. This uniqueness is given to it by the nuclear quantum effect, which is understood as the role of the ZPE of water or the zero energy of the quantum harmonic oscillator -О-Н, proton tunneling, entanglement of quantum fluctuations, competition of thermal and quantum fluctuations.

In water ℏω≪kT and quantum effects are covered by thermal fluctuations. They are visible only in its kinetic properties, where quantum fluctuations play a prominent role.

Now the minimum on the temperature dependence of the isothermal compressibility of water at 46 0С becomes clear. This is explained by the presence of water structures LDL and HDL with a size of 1–2 nm. According to the results of the article

feature of the temperature dependence of the isothermal compressibility of water should be represented as follows. Quantum fluctuations of the O-H bond of torsion and tension of water and H-bonds oscillate in a double-well potential with proton tunneling. The energy compromise is maintained so that the energy of quantum fluctuations is equal to the energy of thermal fluctuations to maintain the minimum Gibbs energy of formation of microcavities in water.

Huge energy bursts starts with very high speed from giant objects and because they covers long distance instantly so they comes in contact with instant gravitational affect parallelly this thing indirectly supports in traveling upto Interstellar distances but not in all cases without presence of any medium. And also said thing is only about how radio bursts covers more distances. Because there's is no uniform distribution of mass and energy in all directions upto all distances in Universe so any such possibility cancel itself. Only thing lefts here is how sound is affected by gravity and vice versa.

Thank you sir Muhammad Wisal . I will read it.

Interesting query, Prof. Stanislav Dolgopolov

I do believe in both quantities Δ(T) and Δ_0, but what is does not seem to be clear at this very moment in the literature is that the ratio Δ₀/k_B T is a universal number, even for BCS in superconducting elements.

Kind Regards.

Hi Prof. Stanislav Dolgopolov

In addition to all interesting posts, the answer is: Yes, they can be annihilated as a coherent boson matter state of a suppercurrents in several ways:

Experimenters do it also, but in different way:

Kind Regards.

See the following post:

As a naive observation on R. Monnier's argument of available final states:

The Fermi-distribution is a continuous function of energy (even though values below 2 kT become very small), so by the argument that pairs break when states become available under the Fermi level, the superconducting phase transition should be continuous, not jump-like as typically observed.

Dear Shalu Pathak ,

you are right, all these peaks arise from parallel planes.

The 003 planes are paralell to the 006 planes, and paralled to the 009 planes etc, but parallel to the 002 and the 001 planes as well.

However their interplanar distances are different und thus the diffraction peaks show up at different angles

Alltogethers all these planes are multiple order planes of the 001 plane.

Please remind the Bragg law:

n*lambda= 2*d*sin(theta)

You may rewrite this equation as:

lambda= 2*d/n * sin(theta)

one also has for any d(_h,k,l)/n = d_(nh,nk,nl)

You may check the validity of this equation for all crystal systems.

The formulas for d_hkl are for example summarized in the attachment, taken from the Klug&Alexander book on 'X-Ray Diffraction Procedures'...

Ggod luck and

best regards

G.M.

You are most welcome, Prof. Stanislav Dolgopolov

In our group that works on unconventional superconductors with strontium, we have found the zero energy gap parameter Δ₀ to be between 0.1 and 1 meV to reproduce well-established theories in the triplet compound strontium ruthenate using a Wigner distribution approach.

Check please for the one last publication, link to the DOI for the manuscript:

But in HTSC with doped nonmagnetic strontium, Δ₀ can be between 10 meV and almost 70 meV if the nonmagnetic disorder is high using the same Wigner distribution approach.

Check our last electronic publication, the link we the manuscript in the DOI

Best Regards.

Of course not.

Well, they lead to the localization of light which are transversal waves and have a sort of elliptical polarization, among many other interesting phenomena, Prof. Stam Nicolis

You can check for example:

Best Regards.

Thank you for the reference. The spin-mediated interaction between electrons takes place. However, for the superconductivity the spin interaction seems to be too weak, because the distance between electrons in a pair may be up to 100 nm, much larger than distances of spin-mediated forces.

A good review to complement the answer by Prof. Stam Nicolis on time reversal symmetry is the classical book by Prof. A. Messiah, the chapter on symmetries and invariance, in the old separate version it was chapter XV, Dr. Abhirami Saminathan

Best Regards.

Agree on that point, Prof. Waldemar Łasica

Best Regards.

You are most welcome, Prof. Rajaji Vincent

you can use this link for unfolding band structure:

Yes, a qualitatively correct description is a precursor for an accurate approach. For the above considered problem a brief description is : in superconductors there are two electronic components (SC electrons, normal electrons), distinguishable in the momentum space. That is every electron belongs to its component as long as the SC state persists, any interchange between components is impossible. Mathematically this mean we should introduce two Fock spaces or two sets of quantum states, which don’t overlap (i.e. there are not common states).

One important consequence: all derivations of conventional theories should be revised within the two-space-approach.

Lithography technique using X-ray can make even sub-micron size gaps in Si wafers. Till now many electronics industries are using the lithography technique only for making Chips.

you should also go for spin hall conductivity and anomalous hall conductivity calculations using Wannier90 package. other important property is exchange parameters, the strength, range and type of exchange parameters plays an important role in determining Curie temperature and macroscopic magnetism of the materials.

The question is very interesting, thank you, Dear Bhargab Kakati

Probably the citing references to the following research article could have a partial answer, unfortunately, I do not have access to it.

Best Regards.

Thank you all for your valuable insights. I think I should have mentioned above that I have not got any high ELF value in the core of Pt atom for the antiferromagnetic arrangement of the system (done with same pseudopotential). The above-mentioned case was for ferromagnetic arrangement. Here I am attaching the AFM elf 2D pattern.

you initialize the magnetic moments of the atoms with the MAGMOM tag in VASP. For calculation with collinear spins, you can set ISPIN=2 in order to run spin-polarized calculations with the MAGMOM tag to the initial values of the magnetic moments for each atom. you must set the MAGMOM tag to

MAGMOM = 1.0 -1.0 -1.0 1.0 knowing, you should follow the same order as in the POSCAR file.

If you want to calculate non-collinear magnetic systems (or if you include spin-orbit coupling in the calculations with LSORBIT=.TRUE. , by which the LNONCOLLINEAR tag is automatically set to true also) then you should specify the x y and z components of the magnetic moment for each atom, again in the same order as the atoms appear in the POSCAR file.

Prof. Stanislav Dolgopolov

A simple answer, electrons at the Fermi level are given by the equation p_F = ℏ k_F if they are around the Fermi surface then there is a linear approximation to that equation: δp = ℏ ( k - k_F ), i.e., which is consistent for most normal metals and serves well for the Fermi-Dirac distribution, the Sommerfeld expansion, the Fermi liquid theory and the concept of quasiparticles.

In addition, electrons are fermions which means they can only occupy one state with one value for spin +/- 1/2, therefore a Fermi Dirac distribution in momentum space implicitly shows that electrons are separate in momentum space if they are treated using QM and for 3 approximations, the free, the quasi-free, and the tight-binding ones.

Best Regards.

https://www.nature.com/articles/nature13915 (1240 citations)

Hi Joseph,

Is your problem solved now?If yes,then can you please tell how did u solve this issue?

I am also facing same problem now.

Please, have a look the following lecture: http://qpt.physics.harvard.edu/talks/upenn.pdf

Dear Shlu,

As shown in 4he attached figure , the charge current flows from left to right through a conductor Hall bar. If the charge current is non-polarized (with equal numbers of spin-up and spin-down electrons), the spin imbalance does not induce a charge imbalance or transverse voltage at the Hall cross. If electrons, which are polarized in the direction of magnetization M, are injected from a ferromagnetic electrode while a circuit drives a charge current (I) to the left, a spin imbalance is created. This produces a spin current (I_S) without a charge current to the right of the electrode. Spin–orbit interactions again separate spin-up and spin-down electrons, but now the excess of one spin type leads to a transverse charge imbalance and creates a spin Hall voltage, VSH. As the distance, L, between the electrode and the Hall cross increases, the voltage signal decreases, allowing the decay length of spin currents (spin diffusion length l_sf) to be measured. More details about SQHE will be presented in Chapter 9 of my Book, about spin transport in nanostructures.

Dear Shalu Pathak, in addition to all the interesting answers,

To understand the role of nonlocality between the current j_a(z) and the electrical field applied E_b(z´) to a normal metal, i.e.,

j_a(z) = (integral from 0 to infinite) K(z,z')_ab E_b(z´)

where the radius of the kernel K(z,z')_ab ~ l (the mean free path) please review section 3 of the classical work:

Best Regards.

You distinguish a normal classical Hall efect from a Quantum Hall effect.

Normal size devices exhibit the first, contain considerable number of electrons.

The magetic field acting on the current pushes electrons to one side of the device

and is counteracted by the Hall voltage set up from charge accumulation. Proportionality between magnetic field and Hall voltage for steady current.

Quantum devices contain fewer electrons in narrow or small devices (Nanostructures) . The magnetic field provokes the equivalent of Landau levels that contain the states for electrons. These pass at regular intervals as the magnetic field increases. Thus there are regular jumps

in the electron conductance as magnetic induction increases.(In single electron conductance, or normal quantum hall effect

The fractional quantum Hall effect is believed to be the consequence of electron interactions and quasi particle formation. This is an extremly complicated phenomena, and not nearly as well understood as many would have you believe.

I will second Hadi Jabbar Alagealy here, that paper is all.

Quantum materials are I believe are those materials that exhibit wave behavior, or equivalently particle-wave duality.

Please tell me more

Thank you so much for your post, Prof. Hadi Jabbar Alagealy

Very interesting to know that TB helps in the study & understanding of electron transfer in solid-state devices.

Best Regards.

Dear Ankit Yadav,

The electron affinity x=Evac-Ec, is a material characteristic, just like the energy gap. You can only change it by changing the material, e.g., by heavily doping of the semiconductor, so that Ec is shifted or by changing the operating temperature

This paper is related to this thread:

Dear Kaushick Parui , In addition to all those mentioned, the chapter VII of the book:

Statistical Physics, part II: Theory of the Condensed State, Vol. 9 by E. Lifshitz, L. Pitaevskii Elsevier, 2013.

for the Ph.D. Level - Theory. Mainly talks about magnons.

Best Regards.

Indeed Dear Ahmed MS Dawelbeit it is a very interesting and subtle question, refer to it as a localization phenomenon is one way since electrons can be seen as wave packets that can be or not well defined within the structure (metal, either metallic polimer).

In general, we have a kinetic criterium with three well-defined regions, the product "l . k_F", since we understand localization as the absence of diffusion of any kind of waves in a disordered medium.

Please check for the case of metallic polymers, the following reference:

Alan J. Heeger, 2003, The Critical Regime of the Metal-Insulator Transition in Conducting Polymers: Experimental Studies. Condensation and Coherence in Condensed Matter, pp. 30-35

it is very instructive

Negative binding energy (BE) means the complex/crystal is bound Spontaneously without consuming energy (i.e. more -ve BE means more stable) however if it is positive that means, one has to give that much amount of energy to form the crystal/complex. Both signs (+ve or -ve BE) are acceptable, only the main difference is that if BE is -ve then there will be the release of energy during the crystal/complex formation whereas in the case of its +ve value means one has to give that much energy to construct the crystal/complex.

I hope this answer will help to understand...

The electric filed in the dielectric is E= V/d = 1 V /(10^-7) m = 10^7 V/m

Because you apply the voltage with a metalic electrode on top of the gate the electric field in the dielectric is less than 10^7 V/m with the Schottky barrier

1V- (50 -100 mV) for Al2O3

Dear Franklin Uriel Parás Hernández ,

for the exciton Bohr radius ofhexagonal boron nitride

please see the abstract of:

Solid-state Physics, go back to the old terminology, Prof. Muhammad Hamza El-Saba

I elaborate, nowadays we see many papers with titles such as "nematic supercoductors", but as far as I can recall, a solid-state crystal (solid-state) is not a nematic liquid crystal (condensed matter liquid phase, not just fluid one).

The phenomenological physics based on "free Helmholtz & Gibbs energies" for liquid crystals is something really very "very" hard to calculate and to study, and that is only the classical part of the subject. I cannot imagine how is to deal with by adding quantum correlated many-body phenomena to systems such as liquid crystals.

I can advise reading chapter VI on "the mechanics of liquid crystals" from the book: Theory of Elasticity by Lifhsitz Kosevich & Pitaelskii, 1986, Elsevier, which was previously the Landau Lifshitz VII volume, to understand what I mean.

Best Regards.

you can use fluka software

Dear Ghulam Murtaza sir, I agree with all the above answers.

One can easily judge the position of fermi level using the conventional formula.

Second, increasing the doping density in semiconductor will increase the number of charge carriers(let's say n type semiconductor). This increase in number of free charge carriers will disturb the charge distribution in the semiconductor and the fermi level now starts moving away from the intrinsic fermi level. This shift is proportional to the log of doping density. So, more the doping, more the fermi level will move away from the intrinsic fermi level(centre). While, decreasing doping moves back the fermi level towards the centre.

In case of highly doped semiconductors, one can find the fermi level deep inside the CB(for n-type)/VB(for p-type).

The microscopy mechanics of superconductivity in Sr₂Ru0₄, Prof. Abdolazim Hasseli

Best Regards.

As a preliminary question:

1. which sort of material is your device made of? (metal, semiconductor, organic, other?),

2. what is the topology of the conducing layer (3D, 2D, 1D, powder-like, etc...)?

3. and what is the size of the active layer (cm or mm or µm or less)?

As a matter of fact, in a material with a low number of electrons, even a moderate number of electronic traps can capture electrons and greatly affect the conductivity. This is however unlikely in a metallic device.

Khadka B. Chhetri

You can try with Swissparam to generate required force-fields parameters.

Please follow the link:

Upload your structure in .mol2 format. You can use Avogadro or Jmol to prepare the structure in .mol2 format. Once prepared, run the .mol2 structure and wait for few minutes to get output file from Swiss param based software and then do the required changes for the force-field parameters.

It is because SdH oscillation can only occur for those carriers with sufficiently high mobility, whereas in a Hall measurement all carriers are taken into account. So, in cases where transport happens through multi carriers with both high and low mobilities, you may notice such a difference in the value of carrier density obtained from these two measurements.

Prof. Azeez Abdullah Barzinjy

Thank you so much for pointing out in this thread the classical textbook by Prof. S. Flugge on practical quantum mechanics, which has served well many generations of physicists.

The book definitely, treats extensively and pedagogically the elastic scattering problem in non-relativistic QM, and also there are a couple of problems dedicated to the phase shift problem and bound states.

Best Regards.

As per my knowledge for Fe+2, the number of unpaired electrons is 4 and Magnetic moment will be 4.89 BM.

For Fe+3 ions, the number of unpaired electrons is 5 and magnetic moment will be 5.9 BM.