arXiv subjects

Navinder Singh Bathinda

Publications and source records attributed to Navinder Singh Bathinda.

At least 37 records · Page 2Linked to original sources

arXiv2022

A Concise History of the Black-body Radiation Problem

The way the topic of black-body radiation is presented in standard textbooks (i.e. from Rayleigh-Jeans to Max Planck) does not follow the actual historical timeline of the understanding of the black-body radiation problem. Authors believe that a presentation which follows an actual timeline of the ideas (although not a logical presentation of the field) would be of interest not only from the history of science perspective but also from a pedagogical perspective. Therefore, we attempt a concise history of this very interesting field of science.

physics.hist-ph↗

arXiv2022

Why is Superconductivity absent in bulk Infinite-layer Nickelates?

We answer in affirmative the absence of superconductivity in bulk prepared samples of doped infinite-layer Nickelates through a simple magnetostatic model. In an independent approach we also employ Density Functional Theory (DFT) calculations for the same investigation. Our investigations reveal that it is the formation of Nickel clusters and Nickel deficient regions in bulk prepared samples (as opposed to thin films) that leads to the absence of superconductivity in bulk prepared samples.

cond-mat.supr-con↗

arXiv2022

The Case of Itinerant Magnetism in CaMn$_{2}$Al$_{10}$: Self-Consistent Renormalisation (SCR) Theory Study

We have applied the powerful self-consistent renormalization theory of spin fluctuations for the system CaMn$_{2}$Al$_{10}$ discovered in 2015 and was conjectured to be an itinerant magnet. We have calculated the inverse static (paramagnetic) susceptibility and have compared it with the experimental data (Phys. Rev. B 92, 020413, 2015). The agreement is very good. We have calculated spin fluctuations at various temperatures and have also estimated the strength of the electronic correlation i.e., ($I=0.3136$ eV) in the Hubbard Hamiltonian. Based on our quantitative explanation of the inverse static (paramagnetic) susceptibility data within the framework of SCR theory, we can decisively conclude CaMn$_{2}$Al$_{10}$ exhibits the phenomena of itinerant magnetism. Further, our DFT and DFT+U calculations corroborate the strong Mn-Al hybridization which is the key behind the itinerant magnetism in this system. Our estimated correlations strength will provide a foundation for further studies of itinerant magnetism in this system.

cond-mat.str-el↗

arXiv2021

Plea to publish less

Recent research\cite{fort} has shown that in the 20th century there is an exponential growth of the number of published scientific papers, but new ideas has only a linear growth with time. The 19th and the first half of the 20th century saw major scientific discoveries. But from the second half of the 20th century, the number of publications far exceeds the number of impactful discoveries. Does an exponentially growing number of publications indicate an element of pathological research? Pressure to publish a large number of papers has led to the phenomena of overproduction, unnecessary fragmentations, overselling, predatory journals (pay and publish), clever plagiarism, and deliberate obfuscation of scientific results so as to sell and oversell. This is harming the healthy scientific culture of passion driven research. It is an urgent problem which needs attention of the whole of the scientific community. Some ways to mitigate these grave problems are discussed.

physics.soc-ph↗

arXiv2021

Density-Driven Resistance Response in $MnS_{2}$: Theory

A colossal insulator-to-metal transition in high-spin pyrite phase of $MnS_{2}$ has been experimentally observed \cite{colomns2}. There are two possibilities behind this colossal insulator-to-metal transition: (1) migration of $Mn$ electrons to unoccupied $S^{2-}_{2}$ antibonding states under pressure which leads to conducting ligand states and hence metallic transition, and (2) possibility of band crossing transition. We have analyzed this experimental obervation theoretically using a toy statistical model and found that the transition is due to the migration of electrons from the transition metal ions to the ligand sites (i.e. the possibility (1)). The calculated resistivity compares well with the experimental data within the fitting parameters of the model.

cond-mat.str-el↗

arXiv2021

Background for the Self Consistent Renormalisation (SCR) Theory

A detailed review is given on the evolution of the theory of itinerant magnetism. The self-consistent renormalization (SCR) theory is quite successful in addressing the phenomenon of itinerant magnetism in weakly and nearly ferromagnetic and anti-ferromagnetic materials. It goes beyond the Stoner and random phase approximation (RPA) theories in taking the correlation effects into account. The Mathematical machinery of the SCR theory is rather complicated. The aim of these notes is to provide the required background. The problems with Stoner and RPA theory are discussed and the way in which the SCR theory rectifies those problems is also discussed.

cond-mat.str-el↗

arXiv2021

A toy model for localized to itinerant electron transitions

A toy statistical model which mimics localized-to-itinerant electron transitions is introduced. We consider a system of two types of charge carriers: (1) localized ones, and (2) itinerant ones. There is chemical equilibrium between these two. The solution of the model shows that there is a crossover, at a specific value of a local interaction energy parameter $J$, at which carriers transfer from being itinerant to a localized/mixed valence state. The model has a very crude analogy to the observed $γ\rtaα$ transition in metal cerium.

cond-mat.str-el↗

arXiv2020

Leading theories of the cuprate superconductivity: a critique

We present a review of the leading theoretical approaches in the field of cuprate high temperature superconductivity. We start out by defining the problem and ask the question: whether an overarching theory possible (which is capable of explaining not only the mechanism of unconventional superconductivity but also a coherent understanding of the strange metal phase and the pseudogap phase)? If it is possible, what should we expect from the overarching theory? We list various experimental facts, and point out what can we learn from them and where do current theories stand in addressing them? Next, we present a critique of the current leading approaches. We conclude that although progress in the field has been unprecedented, but we still lack a coherent understanding.

cond-mat.supr-con↗

arXiv2020

On the airborne aspect of COVID-19 coronovirus

It is a widely accepted view that COVID 19 is either transmitted via surface contamination or via close contact of an un-infected person with an infected person. Surface contamination usually happens when infected water droplets from exhalation/sneeze/cough of COVID sick person settle on nearby surfaces. To curb this, social distancing and good hand hygiene advise is advocated by World health Organization (WHO). We argue that COVID 19 coronovirus can also be airborne in a puff cloud loaded with infected droplets generated by COVID sick person. An elementary calculation shows that a $5~μm$ respiratory infected droplet can remain suspended for about 9.0 minutes and a $2~μm$ droplet can remain suspended for about an hour! And social distancing advise of 3 feet by WHO and 6 feet by CDC (Centers for Disease Control and Prevention) may not be sufficient in some circumstances as discussed in the text.

physics.pop-ph↗

arXiv2019

A theory of resistivity in Kondo lattice materials: the memory function approach

We theoretically analyse D.C. resistivity($ρ$) in the Kondo-lattice model using the powerful memory function approach. The complete temperature evolution of $ρ$ is investigated using the Wölfle-Götze expansion of the memory function. The resistivity in this model originates due to spin-flip magnetic scattering of conduction $s$-electron off the quasi-localized $d$ or $f$ electron spins. We find the famous resistivity upturn at lower temperature regime ($k_B T<<μ_d$), where $μ_d$ is the effective chemical potential of $d$-electrons. In the high temperature regime $(μ_d<<k_B T)$ we discover that $ρ\propto T^{\frac{3}{2}}$. The worked out theory is quantitatively compared with experimental data and reasonably good agreement is found.

cond-mat.str-el↗

arXiv2019

A "road-map" of Nickelate superconductivity

We comment on the electronic structure of Nickelate system $Nd Ni O_2$ which shows superconductivity on doping. The doped system $Nd_{0.8}Sr_{0.2}NiO_2$ shows (most probably unconventional) superconductivity with transition temperatures ranging from $9~K$ to $15~K$\cite{dang}. The resistivity of the parent compound $Nd NiO_2$ shows a minimum at around 60K, and an up-turn at lower temperatures. In the current understanding it is thought to be originating from a Kondo like coupling between mobile d-states of the $Nd~5d$ bands and un-paired electrons in $Ni 3d_{x^2-y^2}-O2p$ hybrid orbitals of $Ni^{1+}$ and $O^{2-}$ions. In this note we offer alternative possibilities of the observed resistance minimum in $LaNiO_2$. We attempt to construct a "road-map" of various possibilities to comprehend the observed behaviour and suggest further experiments to prove or disprove a given explanation. We also compare and contrast Nickelates with Cuprates. Comparison points towards unconventional superconductivity in Nickelates.

cond-mat.supr-con↗

arXiv2019

An attempt to settle the one-component versus two-component debate in Cuprate high-$T_c$ superconductors

Related to the electronic structure of cuprate high-Tc superconductors there are two prevailing views: In one view, Pines and collaborators argue that cuprates consist of two electronic subsystems: one with localized spins and the other having itinerant character. Contrary to that, Phil Anderson has argued for one-component or one-band model for cuprates. Thus, a very natural question arrises: What is the actual electronic system in cuprates? Are these two-component or one-component systems? After a careful consideration of both the views, we argue in favor of one-component or Andersonian view. The key lies in the dual character of electrons in narrow d bands, and we put forward a semiclassical model using which we could quantitatively account for oxygen NMR shift data in $La_{2-x}Sr_xCuO_4$ within the single component view.

cond-mat.supr-con↗

arXiv2019

Comment on arXiv:1807.08572: a plausible explanation of the giant diamagnetism found in Au-Ag nanostructures

In a recent comment (arXiv:1906.05742) on the preprint (arXiv:1807.08572) entitled "Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures", it is pointed out that the reduction of the four-probe resistance ($R_{4P}$) to zero value is accompanied by a rise in the two probe resistance ($R_{2P}$) in the same temperature range. This curious correlation between $R_{4P}$ and $R_{2P}$ is said to be pointing towards a non-superconducting "conductance percolation" transition (rather than "percolating superconducting transition" as proposed in the revised version of arxiv:1807.08572). The explanation offered in preprint arXiv:1906.05742 is quite reasonable, but the author leaves open the question of giant diamagnetism. In this short comment I suggest a plausible cause of the giant diamagnetism found in nanostructures. It could be due to gapped electronic energy spectrum of nanoparticles which is due to quantum confinement effects, and that suppresses the electronic scattering mechanism leading to a very high value of Langevin diamagnetism.

cond-mat.supr-con↗

arXiv2019

A Brief history of mangnetism

In this article an overview of the historical development of the key ideas in the field of magnetism is presented. The presentation is semi-technical in nature.Starting by noting down important contribution of Greeks, William Gilbert, Coulomb, Poisson, Oersted, Ampere, Faraday, Maxwell, and Pierre Curie, we review early 20th century investigations by Paul Langevin and Pierre Weiss. The Langevin theory of paramagnetism and the Weiss theory of ferromagnetism were partly successful and real understanding of magnetism came with the advent of quantum mechanics. Van Vleck was the pioneer in applying quantum mechanics to the problem of magnetism and we discuss his main contributions: (1) his detailed quantum statistical mechanical study of magnetism of real gases; (2) his pointing out the importance of the crystal fields or ligand fields in the magnetic behavior of iron group salts (the ligand field theory); and (3) his many contributions to the elucidation of exchange interactions in d electron metals. Next, the pioneering contributions (but lesser known) of Dorfman are discussed. Then, in chronological order, the key contributions of Pauli, Heisenberg, and Landau are presented. Finally, we discuss a modern topic of quantum spin liquids.

physics.pop-ph↗

arXiv2019

Resistivity of a $2d$ quantum critical metal

We calculate resistivity in the paramagnetic phase just above the curie temperature in a $2d$ ferromagnetic metal. The required dynamical susceptibility in the formalism of resistivity is calculated within the Random Phase Approximation(RPA). The mechanism of resistivity is magnetic scattering in which $s$-band electrons are scattered off the magnetic spin fluctuations of d-band electrons. We use the $s$-$d$ Hamiltonian formalism. We find that near the quantum critical point the resistivity in $2d$ scales as $T^{\frac{4}{3}}$, whereas in $3d$ it scales as $T^{\frac{5}{3}}$. In contrast to it, resistivity due to phonon scattering is given by $T^5$ in low temperature limit as is well known. Our RPA result agrees with the Self-Consistence Renormalisation(SCR) theory result.

cond-mat.str-el↗

arXiv2018

Clearing certain misconception in the common explanations of the aerodynamic lift

Air travel has become one of the most common means of transportation. The most common question which is generally asked is: How does an airplane gain lift? And the most common answer is via the Bernoulli principle. It turns out that it is wrongly applied in common explanations, and there are certain misconceptions. In an alternative explanation the push of air from below the wing is argued to be the lift generating force via Newton's law. There are problems with this explanation too. In this paper we try to clear these misconceptions, and the correct explanation, using the Lancaster-Prandtl circulation theory, is discussed. We argue that even the Lancaster-Prandtl theory at the zero angle of attack needs further insights. To this end, we put forward a theory which is applicable at zero angle of attack. A new length scale perpendicular to the lower surface of the wing is introduced and it turns out that the ratio of this length scale to the cord length of a wing is roughly $0.4930\pm0.09498$ for typical NACA airfoils that we analyzed. This invariance points to something fundamental. The idea of our theory is simple. The "squeezing" effect of the flow above the wing due to camber leads to an effective Venturi tube formation and leads to higher velocity over the upper surface of the wing and thereby reducing pressure according the Bernoulli theorem and generating lift. Thus at zero angle of attack there is no need to invoke vortex and anti-vortex pair generation. In fact vortex and anti-vortex pair generation cannot be justified. We come up with the equation for the lift coefficient at zero angle of attack: \[C_l = \frac{1}{c}\int_0^c dx \left(\frac{h_c^2}{(h_c - f(x))^2}-1\right).\] Here $C_l$ is the lift coefficient, $h_c$ is our new length scale perpendicular to the lower surface of the wing and $f(x)$ is the functional profile of the upper surface of the wing.

physics.pop-ph↗

arXiv2018

A plausible explanation of the repeated "noise" pattern in the data of arXiv:1807.08572: quantum confinement and surface phonon modes

A key point from the experiment related to the "noise" pattern in figure 3(a) of arXive:1807.08572 is that it is a function of temperature. We put forward a possible explanation. We argue that it is the elasto-magnetic coupling in which the diamagnetic surface currents on the surface of nanoparticles couple to surface phonon modes. As the temperature is increased (say from 210 K to 220 K), successive phonon modes are excited, one by one. This is due to quantum confinement where phonon modes take discrete values of energy (in bulk, the modes are quasi-continuous). One by one excitation of phonon modes modulates the surface currents on nano-particles that led to a fluctuating magnetization thus "noise" in the lower part of the susceptibility data where the system is in the superconducting state.

cond-mat.supr-con↗

arXiv2018

The story of magnetism: from Heisenberg, Slater, and Stoner to Van Vleck, and the issues of exchange and correlation

This article is devoted to the development of the central ideas in the field of magnetism. The presentation is semi-technical in nature and it roughly follows the chronological order. The key contributions of Van Vleck, Dorfman, Pauli, Heisenberg, and Landau are presented. Then the advent of the field of itinerant electron magnetism starting with the investigations of Bloch and Wigner, and more successful formulation by Slater and Stoner is presented. The physical basis of the Slater-Stoner theory is discussed and its problems are summarized. Then, an overview of the debate between itinerant electron view of Stoner and localized electron view of Heisenberg is presented. Connected with this debate are the issues of exchange interactions. The issues related to the origin of exchange interaction in Stoner model are discussed. We review the "middle-road" theory of van Vleck and Hurwitz--the very first theory which takes into account the electron correlation effects in the itinerant model. We close our presentation with the discussion of the very important issue of strong electron correlation in the itinerant picture.

cond-mat.str-el↗