Science topic

# Condensed Matter Theory - Science topic

Condensed Matter Theory

Questions related to Condensed Matter Theory

It is well known that non-zero

**negative**exchange energy indicates that a singlet state of electrons is energetically more favorite than a triplet one. Sufficiently strong thermal fluctuations destroy any magnetic spin order, so singlet and triplet order becomes equiprobable in the crystal. Hence below a certain temperature (say T*) the energy gain of the singlet order may be larger than the destroying thermal energy, and then preferred singlet pairs become stable. Thus the pairing energy is the difference between two energies:E1. Energy of the stable singlet;

E2. Energy of the state without spin ordering, where singlet/triplet are equiprobable.

Note: we consider conduction electrons, i.e. electronic wave packets are much larger than lattice constant. So the result is not related with antiferromagnetic order.

This simple logic shows the electron pairing can be derived only from the non-zero negative exchange energy. Feel free to comment or to correct the result.

In this model, the number of density of available states for the charge carriers near Fermi level comes around 10^22. Will this much number come for bulk insulating ceramics. For the calculation of number of density of available states for the charge carriers near Fermi level, f0 (resonance frequency) is taken as 10^13Hz. Why? Could you please help me.

In the BCS theory the pair density depends on temperature, meaning that pairs can be created/annihilated by temperature variations. On the other hand, in some experiments the supercurrent, once excited, runs for many months, indicating that any pair recombination doesn’t take place (pair recombination would dissipate the initial momentum of pairs). Can we solve the contradiction?

Superconducting electron pairs occur on the Fermi surface, where the electron kinetic energy is a few eV. The binding energy of paired electrons is usually a few 10

^{-3}eV, so the electrons seemingly cannot remain paired. However, pairs are stable until thermal fluctuations destroy them. Is the situation paradoxical?Most conventional theories of superconductivity (SC) use the second quantization notation (SQN) where all electrons are assumed indistinguishable, every electron can take every state in the momentum space. However, a sample shows that SQN is insensitive for supercurrent description.

For clarity we consider only 4 electrons (which may belong to arbitrary many-body system): a non-dissipative singlet pair (e1,e2) and two normal (dissipative) electrons e3, e4 . We investigate two cases, A and B:

**A.**The non-dissipative pair (e1,e2) is

**permanent**. Then an initial non-zero momentum Px of the pair is also permanent. Obviously, this permanent Px is a supercurrent;

**B.**The non-dissipative pair (e1,e2) is

**not permanent**, i.e. a recombination is possible: e1, e2 become normal, e3, e4 become non-dissipative and back. But at every time moment there are one non-dissipative pair and two normal electrons:

(e1,e2)singlet + e3 + e4

**<=>**e1 + e2 + (e3,e4)singletIn case B the initial non-zero momentum of the pair (e1,e2) dissipates, because the electrons e1,e2 become periodically dissipative and there is no external force to give to the newly created pair (e3,e4) exactly the same momentum Px, which the pair (e1,e2) had. So the momentum Px of the system dissipates and the current vanishes. Thus non-permanent pairs cannot keep a supercurrent (otherwise the momentum conservation law is violated; the atom lattice took the momentum Px of the broken pair e1,e2, hence Px of the new pair (e3,e4) must be zero). Notable is the fact that both cases A and B are identical in SQN due to equal occupation numbers (in both cases there are exactly two normal and two SC electrons). However, the case A is superconducting and the case B is dissipative. The cause of the paradox is the indistinguishability of electrons.

Thus the SQN principle of indistinguishability of particles is insensitive to the supercurrent description, we should consider the normal and SC-electrons as

**distinguishable, i.e. non-exchangeable in the momentum**space particles.So far nobody could plausibly reconcile this paradox and conventional theories of SC.

A newest

**Nature paper E. T. Mannila et al, "***A superconductor free of quasiparticles for seconds*" https://www.nature.com/articles/s41567-021-01433-7 shows that superconducting (SC) pairs persist at least for seconds. The measurement device detects single pair-breaking-events for a large pair population, so the average life time of each pair is much longer than a few seconds (probably, many hours). Thus, every pair hosts its electrons a long time. In most SC-experiments worldwide, the measurement time is much shorter than the life time of the long-hosting SC-states, therefore we can assert that the SC-electrons and normal electrons are non-exchangeable during the measurement, i.e. the SC-electrons do not hop into normal states (at least during the resistance measurement). If so, then the SC-electrons and normal electrons are distinguishable and the superconductor has two distinguishable electronic components: (i) SC-electrons; (ii) normal electrons.Each of the distinguishable components has its own set of quantum states, its own one-particle-wavefunction, its own Fock space, although the components are overlapped in the real space.

Mainstream theories of superconductivity (BCS etc.) operate within one electronic component and don't take into account this distinguishable 2-component-nature. Should the theories be updated according to the newest finding ?

I read some paper about this subject [ Yen-Chun Peng Optical Material 39 2015; Luis A. Agapito PHYSICAL REVIEW X 5, 011006 (2015) ... ] then they show how to do and some values.

The valence configurations of the atoms were 4s2 3d10 for Zn, 2s2 2p4 for O.

The energy cutoff : 380eV

The change in energy: d-5 eV/atom

maximum force: 0.03 eV/anstrong

maximum stress: 0.05 GPa

maximum displacement tolerances: 0.001 anstrong

The energy convergence criterion: d-6 eV

The Ud value for Zn-3d : 10 eV

The Up value for O-2p orbital: 7 eV

This is my scf file. If someone know where I was wrong please correct me!!!

Many thanks !!!

I am doing a PhD in AdS/CMT. In order to have a better understating of the physics of the systems the correspondence aims to describe, I am looking for accessible reviews or online seminars about the mostly commonly used experimental techniques for probing strongly coupled materials such as the cuprates in their strange metal phase.

when a 2DEG is subjected to the magnetic field, the energy is split in the form of Landau levels. and the QHE is explained on that basis. however, in the case of quantized resistance is obtained without a magnetic field. then how Landau levels are formed in QSHE?

In non-local measurements, we apply current between two leads and measure voltage on different leads away from the current leads. to calculate resistance, do we need to divide the non-local voltage by current - as such current is not flowing through the voltage leads?

can you please suggest good literature on non-local measurements?

Thanks

I have several confusions about the Hall and quantum Hall effect:

1. does Hall/QHE depend on the length and width of the sample?

2. Why integer quantum Hall effect is called one electron phenomenon? there are many electrons occupying in single landau level then why a single electron?

3. Can SDH oscillation be seen in 3D materials?

4. suppose if there is one edge channel and the corresponding resistance is h/e^2 then why different values such as h/3e^2, h/4e^2, h/5e^2 are measured across contacts? how contact leads change the exact quantization value and how it can be calculated depending on a number of leads?

5. how can we differentiate that observed edge conductance does not have any bulk contribution?

What are the quantum materials? Quantum phenomenon takes place in every material at atomic level. then how to define quantum materials? is Iron (magnetic materials) quantum material as it shows magnetism which is the quantum phenomenon? if not then what are quantum materials?

The Nilsson diagram is obtained by solving the Schrodinger equation. If the deformation parameters are continuous, I wonder the orbits should be continuous as well. If the Pauli exclusion principle is the reason, the nilsson quantum number are not always equal, such as 5/2[402] and 5/2[642], why?

Dear and Distinguished Fellows from the solid-state physics R

^{G}community.Does have anyone read after 20 years the preprint from Prof. Laughlin

*A Critique of two metals?*I read it when I was a PhD student. I think his opinion after 20 years deserves more attention. Please, feel free to follow down the link to the arXiv preprint if somebody has an interest and please leave your opinion:

Article A Critique of Two Metals

Dear

*community, this review thread is about the role of RKKY interaction in solid-state physics. I want to learn more about it. I would like to know for example, what physics effects RKKY describe well.***R**^{G}

*The RKKY exchange interaction (Ruderman - Kittel - Kasuya - Yosida) is defined as an indirect exchange interaction between magnetic ions, carried out through itinerant conduction electrons.*In rare-earth metals, whose magnetic electrons in the 4f shell are shielded by the 5s and 5p electrons, the direct exchange is rather weak and insignificant and indirect exchange via the conduction/itinerant electrons gives rise to magnetic order in these materials.

*Some initial clarifications:**For this thread, the are two types of electrons: itinerant or conduction electrons and localized electrons.***Indirect exchange**is the coupling between the localized magnetic moments of magnetic metals via the conduction electrons, while**direct exchange**occurs between moments, which are close enough to have sufficient overlap of their wavefunctions.

**RKKY interaction takes place in metals and semiconductors**, where itinerant electrons mediate the exchange interaction of ions with localized oppositely directed spins, partially filled**d**

*and*

**f**

*shells.*

*The physical mechanism is the following:*

**Conduction/itinerant electrons interact with the effective magnetic field of the i-th site**of the crystal lattice and**acquire a kind of spin polarization**. When passing through the next lattice site**, relaxation of the magnetic moments of the electron and the site will cause mutual changes in both the spin polarization and the spin of the lattice site.**

**Hereby, RKKY can be described using the concept that conduction electrons move in an effective field created by a localized magnetic moment of one site.**[1] M.A. Ruderman and C. Kittel, Phys. Rev. 96, 99 (1954).

[2] T. Kasuya, Prog. Theor. Phys. 16, 45 (1956).

[3] K. Yosida, Phys. Rev. 106, 893 (1957).

[4] D. I. Golosov and M. I. Kaganov, J. Phys.: Condens. Matter 5, 1481-1492 (1993).

Hello, I'm trying to understand the calculation of Green functions in dirty metals. Typically, in such calculations the contributions of Feynman diagrams with intersecting impurity lines are neglected. An explanation of this can be found in the textbook of Abrikosov, Gor'kov and Dzyanoshinsky, but I don't quite understand it. It is said in the book that when integrating over momenta, the region far from the Fermi surface simply renormalizes the chemical potential. This is clear for a diagram with two crosses, however, not obvious at all for more complicated diagrams. Is there a renormalization trick involved? Could you offer an explanation, or direct me to another source with a more detailed discussion of the matter?

I am a graduate student majoring in the condensed matter theory.

Nowaday I want to study the gauge theory on my own, but it is very hard to understand the idea.

So I am finding the open coursewares for gauge theory but I cannot find one.

Would you help me?

What could be the reason for a charge up in a device. I noticed that when I measure the temperature dependence of resistance, at the lowest temperature there is i very sharp increase in resistance. this increase depends upon waiting time at the lowest temperature. Why device charge up with time. if I restart measurements again, it starts from the initial value.

please someone experienced this?

For the simulation purpose, I need force-field for Mn3O4. I searched and tried a lot but almost unable to get appropriate force-field parameters for it. Can anyone help me by suggesting or availing it ?

Generally, when we calculate the carrier density in 2DEG from SdH oscillations (Field dependence of sheet resistance) and QHE (field dependence of Hall resistance) it should match. In some cases it was found that carrier density calculated using both data differ. What is the reason behind this difference? What is the physics behind the calculation of carrier density from SdH oscillations and Hall resistance data?

The second quantization notation operates with occupation numbers. For electrons within a quantum system the occupation number of each state is 1 or 0. However, local states in crystals do not necessarily overlap in the real space, and, thus, in one crystal can exist manifold identical local states. Does it mean that the occupation number is also larger than 1 ? How we can use the second quantisation in this case ?

The Meissner effect is the expulsion of a magnetic field from a superconductor during its transition to the superconducting state. Entering the superconducting state, electric currents are set up near its surface and this cancels the applied magnetic field within the superconductor. So, it seems that electron movements become possible which were not before possible and this is demonstrated by the Meissner effect. Does this amount to emergent degrees of freedom relevant to the 2nd law of thermodynamics?

Hello Everyone,

Recently I am doing some

**Phonon**branchesbased studies. For some materials the gap between the**optical and acoustic branch**is small, for some it's large and for some there is no gap.So how this gap affects the material property or what is its physical significance?

Thanks,

Abhinav Nag

Science does not stand still. New opportunities for research keep appearing and, as a result, new findings and discoveries happen hand to hand with artifact discoveries. These discovery some time with considerable controversy in the literature, sometimes at unusually impoliteand unprofessional levels. Some time artifact discoveries also surprised the world of science.

1) Different groups presents different results on same material and trying to prove each other results as wrong. Is it not sicietificy sound if these groups exchange specimens before they claim the work of others is simply wrong?

2) In some cases materials have been considered to be with ground breaking discovery when the data can be interpreted more simply via other well-known mechanisms. Is it not import to look wider before claims a breakthrough discovery?

3) In some cases the experimental results are true, despite theory implying that this is not possible. Is it appropriate to reject a experimental output just because theory doesn't exits which can explain it?

4) Controversy and attention on a new anomalous phenomenon such as Room Temperature Superconductivity.

In standard text books about Superconductivity like "Buckel" one learns that two fermionic electrons (each spin s=1/2) couple and form a boson with total spin of S=0, which is a singlet state (the spins are anti-parallel).

Is there anything preventing them from forming a triplet state S=1 (the spins are parallel)?

Is it related to symmetry considerations?

What would be the consequences of a S=1 state?

I am currently reading some papers in the field of high Tc superconductivity. Some concepts confuse me. Can you tell me the definitions of spin wave, spin density wave, spin excitation, spin fluctuation, spin gap, charge density wave and charge order? What are the differences and correlations between these concepts? And, what their relationships with high Tc superconductivity?

Is the Sound Velocity Anomaly a fingerprint of charge order transition temperature or it is a finger print of a temperature where lattice degrees of freedom show divergence? (Which may be due to different reasons.)

I have come across few research articles, where sound velocity anomaly has been take as a fingerprint of charge order phase transition temperature. I believe s

*ound velocity*should changes across any phase transition and thus sound velocity anomaly is just an indication of occurrence of either structural or magnetic or electronic phase transition.*Correct me if*I'm*wrong*By quasi-particle I mean in the sense of particles dressed with their interactions/correlations? If yes, any references would be helpful.

I wish to do DFT calculations and use the frozen phonon approach via Phonopy. Should I pay attention to the magnetic moments?

Sometimes, individual atoms in a crystal have different magnetic moments. Does this have any additional effect?

For the transition from insulator to metal, there have different transition mechanisms.

How to distinguish Anderson transition (Anderson insulator was induced by the disorder-induced localization of electrons) from Mott transition (Mott insulator was induced by the Coulomb repulsion between electrons. This transition can be controlled by the mechanisms of oxygen vacancy controlled electron filling), especially in 2 or 3-dimensions materials.

Generally we say that the density of states (DOS) at Fermi level contribute to many phenomenon. However in the Dirac cone DOS is zero at Fermi level. What does it mean and what are its consequences? Why it is important in topological insulators to have Dirac point at the Fermi level. is it not good if Dirac point is in the gap of bulk band structure instead of Fermi level?

I have read Fukui's paper( attached below) and I want to use his method to calculate Chern number on honeycomb lattice. How can I discrete the Brilliouin Zone to fit it's square discretion ?

I know that wave-packet is the super-imposed form of the waves. It is created when some waves have interference and a particle (say electron) can be represented by a wave-packet. I am bit confused actually a single wave is associate with a particle then why in case of wave-packet we associate more then one wave with a particle?

I know that when we plot band structure i.e E vs. k, the shape is parabolic. But when we plot band structure for E vs k, where k is different points (gamma, M, K or K') of Brillouin zone edge points, why it is not parabolic and have other interfering bands?

Please see the attached images (from Google).

Graphene Electronics Vs Silicon Electronics !!

Silicon has a band gap of 1.1 eV but graphene is zero band gap semi metal. Therefore graphene has a very less scope in achieving the goal. Further, Doped graphene layer can have certain band gap which can be used in electronic applications similar enough to those using Silicon.

stacking one layer on another monolayer of graphene in a 'magic angle' changes the properties of the bilayer significantly. Which phenomenon will be responsible for the superconductivity. I already encountered lesser conductivity of ordinary bilayer as compared to that of a monolayer graphene.

Sometimes researchers getting new results out from the similar experiments done by other researchers. But, if they propose some new phenomena against the existing one, the scientific community is not easily accepting. So far I observed, people, trusting, following and try to prove the scientific phenomena (physics) proposed by well-known persons in scientific society. If those results not accepted by any high impact journal community, still, it get accepted by a low impact journal community which infer proposed phenomena were not studied properly.

Would you mind to tell what is real science then? What's exact factor decides the quality of scientific phenomena?

Please help me to clarify doubts on it

Is there any better technique relative to one reported by Kwon and co-workers, The

**interfacial segregation growth technique**using Graphite powder coating on a poly-crystalline Ni layer (deposited on the glass substrate) yields High crystalline quality of single- layer graphene synthesized at low temperatures? Since in this case, the**problem lies in the deposition of Ni on the glass and then it's removal after the growth**.can someone please explain me in simple physics that why spin-orbit coupling is relativistic?

**Von- Hove singularities are said to be non-smooth points corresponding to M-points in first B.Z.**What do they actually signify?

Degeneracy of electrons in graphene is 4. 2 for isospin and 2 for real spin. How do we get the degeneracy here?

Generally band E-k band diagram of a material look like parabolic type. However this is not the case in the TIs. Why bands in TIs are like this (Fig. shown)? Is it due to spin-orbit splitting however generally this type of splitting is seen on the energy axis and not on the k-axis.

Hello everyone,

I have written a small code that performs linear Spin Wave for simple antiferromagnetic Heisenberg Hamiltonian. It takes spin Hamiltonian as an input and performs Holstein-Primakoff, Fourier transformations as well as linearization.

Now, I would like to extend it for the further neighbors. Now, let's say, I have a site A and a cite B, and now I add A2 and B2 sites to my model system, so that I can add, let's say, J_2*\vec{S_A}*\vec{S_A2} Heisenberg term to my initial model. Do I have to add J_1*\vec{S_A2}*\vec{S_B2} aswell? And what about the boundary conditions then?.. Also, if I add a third neighbor, I am working with a decently sized cluster already...

Also, in my case, I expect system to stay bipartite, i.e. have two magnetic sublattices. But what if I don't know what the magnetic order would be?

Thank you!

Ekaterina

I am calculating the size of the CdS quantum dot by using Brus equation from the TAUC Plot. so, in that brus equation contains reduced mass of electron and hole as shown in uploaded figure. where can I found these values?

We all know one of the most widely studied phenomena in condensed-matter physics is Kondo effect.

Very briefly the milestones are as follows: This field began in 1933 when Wander Johannes de Haas and co-authors reported an unexpected rise in the resistivity of some gold samples at low temperature [1]. First, Phil Anderson formulated a microscopic model of how local moments form in metals with magnetic impurities. Anderson showed that Coulomb interactions are the reason the magnetic impurity behaves like a local moment [2]. Jun Kondo calculated the scattering rate of conduction electrons from local moments to second order and was able to reproduce the low temperature upturn and the depth of the resistivity minimum [3]. In Kondo's solution the calculated logarithmic divergence cannot physically persist to zero temperature. The zero-temperature limit remained unsolved. The calculated logarithmic divergence cannot physically persist to zero temperature. Renormalization group was required to solve this so-called Kondo problem [4]. It has been the subject of numerous reviews since the 1970s. Up to date, various approximate solutions have been introduced.

While Kondo's calculations were able to reproduce the resistivity upturn, There is a dramatic decrease in resistance in the superconductivity phase. What is the relationship between Kondo effect and superconductivity? Does anybody know about the latest work on this issue? Particulary, Is there anyone who is aware of a study about the solution of Kondo problem with DMFT (Dynamical Mean-Field Theory)?

[1] W.J. de Haas, J. de Boer, and G.J. van den Berg, Physica 1, 1115 (1933)

[2] P. W. Anderson, Phys. Rev. 124 41 (1961)

[3] J. Kondo, Prog. Theo. Phys. 32 37 (1964)

[4] K. Wilson, Rev. Mod. Phys. 47 773 (1975)

I know that spin-orbit interaction is between spin and electrons' motion in the orbit. why these two interact? why spin-orbit is always relativistic?

In Slave-Boson formalism we define

c

_{i}^{+}=b_{i}f_{i}^{+}then this yields,

<c

_{i}+c_{j}>=<b_{i}f_{i}+b_{j}f_{j}>~<f_{i}+f_{j}><b_{i}b_{j}>with a constrain

Σ(f

_{i}f_{j}^{+}+b_{i}b_{j})=1where

<b

_{i}b_{j}>=δ.- Does δ physically correspond to the number of density of “boson” or “vacancy” (namely “holes”)?

- In strong U limit does the above constrain physically mean “the total number of holes and electrons in a site allways equals to one”?

For the usual doping process, within the resonable bonds we can say that the value of oxygen excess is not very well established, but the ambient highest Tc suggests optimal doping. Remember the GS of the generic phase diagram for the class of layered copper oxide SCs in ½ filled case: We are in the AF Mott insulator state first. We dope hole with small doses.

Which one of the following scenarios is physically true?

1. When the hole concentration started to increase gradually, this causes to create RVB pairs. In a certain value of doping the pair and hole concentration will balance between each other and we will have optimal doping value of intermediate regime.

2. The pairs already exist. When the holes are doped, this will destroys the pairs. In the corresponding doping value, again we will have an optima.

Afterwards, we will begin to loose holes and pairs balance, then a metallic Fermi liquid will occurs in overdoped regime.

Additionally; what is the actual charge carrier for High-Tc SCs? Doublons, holes or pairs?

Reliable examples of second order phase transition have not been found. why? Second order phase transitions, L.Landau and his successors (by Yuri Mnyukh )

When Dirac published his equation he has supposed to have find the spin because probably he found half integer values for the angular momentum. But according to the solutions of this equation, it is clear that the “ns” states correspond to just one spin state, contrary to that is generally supposed.

The two sub-shells of the “np” “nd” and “nf” shell correspond to an additional quantum state to that of the “ns” states, with a different number of states. This is exhibited for example with the Zeeman Effect. This is different from the classical notion of spin according to Uhlenbeck G.E. and Goudsmit S., where the spin hypothesis was proposed to explain the two subshells “np” “nd” and “nf”.

This is also established with the calculation of the magnetic moment of different compounds.

Hi for everyone,

Why is there TM mode as the imaginary part of Graphene conductivity is positive?

Also, why is there TE mode when the imaginary part of Graphene conductivity is negative?

Thanks,

The first work of Bohr has led to suppose that indeed the magnetic moment is the leading property in QM and the work of Sommerfeld also. But the half values Bohr magneton in the experimental measurement of magnetic moment appear as a difficulty. The hypothesis of Uhlenbeck and Goudsmit with the hypothesis of the spin seemed to give a good answer, but the g or Landé factor given by Dirac g=k/(k+1/2) giving good interpretations indicate that we miss one point. Then why use the action just in the wave equation?

Topological phase in condense matter, Wannier calculation, HSE.

It's known that the Density functional theory (DFT) is the most successful approach to compute the electronic structure of matter.

It's useful in the study of matter properties of as optical, electrical, chemical, mecanical, structural, therodynamic and so on...

But, I had never the occasion to applicate it, and I want to know how to applicate this calculation to caracterize thin films as CZTSSe for example.

Iam trying to find effective dielectric constant of two mixtures.i.e. mixing a gas to a nanomaterial. we can use either Maxwell Garnett theory or Bruggeman. In my case the volume fraction is greater than unity. i.e x = Gas / Material is greater than unity which effective medium approximation has to be used Maxwell Garnet or Bruggeman

Hi guys,

This is zhenhua wu, I am asking for some help about the KP hamiltonian of a 2D HgTe/CdTe well.

The BHZ hamiltonian is very successful in describing the TI edge states in a 2D HgTe/CdTe well. Recently people have proved the existence of the weyl semimetal phase in a 3D HgTe crystal with stress (Nat. Comm.

**2016**, 7,11136) and also in the 2D HgTe/CdTe well undergoing a phase transition from the aforementioned TI state by tuning the well thickness (Phys. Rev. Lett. 2017, 118, 156401). A tight binding hamiltonian is given in the ref prl 118, 156401. Is there a 4x4 BHZ kp hamiltonian for HgTe well weyl semimetal which has the same format as that describs the TI state but just with different parameters, like changing the value of M? I hope to get this hamiltonian and directly apply it in the transport simulation utilizing the scattering matrix formalism. Thanks!This is highly related to the critical phenomena in strongly correlated electron systems. Through this challenging question, I would like to invite those active researchers who have long been involved in the field of statistical physics and theoretical condensed matter physics so that we can at least find some clue to proceed ahead.

Since X-ray’s frequency is too big to vibrate electrons, refractive index is nearly 1 to any materials which means its velocity doesn’t change at any environments. Scattering is interaction between bound electrons and light, I think this concludes X-ray can’t ‘feel’ bound electrons. But it does. why?

How to calculate superconducting property or any related parameter of an organic molecule/superconductor using Gaussian 09?

why in bulk semiconductor we assume that effective mass equal to electron mass, but in small one we not assume that?

A postdoctoral research position is available in the Large's group in the Department of Physics and Astronomy at UTSA. The successful candidate will be responsible for conducting research in the area of theoretical and computational nanophotonics and plasmonics. He/She must have a strong background in computational Physics and have previous experience with electromagnetic simulation tools for the modeling of the optical response of metallic nanostructures such as FDTD, DDA, BEM, FEM/FEA, or Green Dyadic method. The candidate should also be familiar with Linux environment and be able to run basic commands in a terminal-like environment, and possess basic programming skills in C/C++, Fortran, Matlab, or any other scientific language. In addition to plasmonic materials, expertise in semiconductor, magnetic materials, two-dimensional materials, or other types of materials will be considered as a plus. The candidate will be working on several independent projects simultaneously and will be involved in both stand-along theory projects and collaborations with experimental groups. The candidate must be self-motivated, methodical, detail-oriented, and possess good oral and written skills.

The position is anticipated to start in Fall 2017 but the starting date can be discussed.

Please send a cover letter detailing your experience, a CV, and the contact information of three references to Dr. Large.

Contact: Dr. Nicolas Large, Nicolas.Large@utsa.edu

Group website: http://physics.utsa.edu/nlarge

Dear friends, i need a brief explanation regarding the energy dependency of nuclear dissipation coefficient. SM analysis of evaporation residue cross section measurement shows both energy dependent dissipation coefficient and constant dissipation coefficient in two independent results. However pre-scission neutron multiplicity analysis also shows, energy dependent dissipation coefficient for reproducing Npre values.

I have read already Dzyallonskii's paper as well Moriyas paper which is the two basic paper discussed and derived the reason of spin canting. However, I am finding it difficult to understand. I do not need any mathematical explanation for my understanding. I just want to know the phenomenological concept behind the spin canting in Hematite. Yes, it is well known that spin canting arises when an isotropic superexchange interaction combined with the Spin-Orbit coupling (SOC). But I fail to have a clear picture about this, means how the SOC gives rise to canting and why it just vanishes below the morin transition in hematite.

I make thin films and I use glasses as substrate. A single grid's dimension in my evaporation system is 16mm x 6mm. I work in 10

^{-6}Torr vacuum.How can I cut my glasses with rectangular geometry?

Many articles states about three interactions (Fe-Fe, Fe-R, and R-R) in orthoferrites either at or below Neel Temperature. Not many evidence were found regarding the predominant interactions at high temperatures and interaction with respect to rare earth concentrations. What will be the effect on the interactions at high rare earth concentrations and at high temperature?

We know that some of the Weyl semimetals show negative magnetoresistance in presence of parallel electric and magnetic fields, which is indicative of the chiral anomaly due to Weyl fermions. But there are other negative linear magnetoresistance (NMLR) phenomena like NLMR in magnetic materials, NLMR due to geometry or size effects of the samples (current-jetting effect), NMLR in quantum limit etc. How to differentiate these NLMR phenomena with the chiral anomaly induced NLMR phenomena ( Adler–Bell–Jackiw chiral anomaly) in a Weyl semimetal?

This question is related to magnetism and application of density functional theory (DFT)

Consider a two eigen wave functions A, B, where A is in the ground state in the lowest frequency mode, and B is in the first excitation state in the highest frequency mode in the Debye model. The expectation value <x> for the deviation from the equilibrium positions in the lattice of the sum A+B, <A+B|x|A+B> would vibrate at 50% higher frequency than the highest frequency allowed in the solid. Is there any principle or rule that eliminate such unallowable higher frequency lattice vibrations caused by the sum of two wave functions in different normal modes in the Debye model?

We know that Allen-Dynes-modified McMillan formula is model dependent formula, where the model describes only real materials which satisfy 4 approximations. The isotropic approximation is one of them. If, in a system, the isotropic approximation failed then is it possible to apply the formalism to estimate the superconducting transition temperature?

In our work , we reported the estimation method for calculating the optical band gap and determining the type of inter band transition. The empirical fitting of experimental data to the law requires the assumption of a value for (3/2 , 1/2 , 2 , 3 )