Giant magnetothermal conductivity and magnetostriction effect in charge ordered Nd0.8_{0.8}Na0.2_{0.2}MnO3_{3} compound

We present results on resistivity ($\rho$), magnetization ($M$), thermal conductivity ($\kappa$), magnetostriction ($\frac{\Delta L}{L(0)}$) and specific heat ($C_{p}$) of charge-orbital ordered antiferromagnetic Nd$_{0.8}$Na$_{0.2}$MnO$_{3}$ compound. Magnetic field-induced antiferromagnetic/charge-orbital ordered insulating to ferromagnetic metallic transition leads to giant magnetothermal conductivity and magnetostriction effect. The low-temperature irreversibility behavior in $\rho$, $M$, $\kappa$ and $\frac{\Delta L}{L(0)}$ due to field cycling together with striking similarity among the field and temperature dependence of these parameters manifest the presence of strong and complex spin-charge-lattice coupling in this compound. The giant magnetothermal conductivity is attributed mainly to the suppression of phonon scattering due to the destabilization of spin fluctuations and static/dynamic Jahn-Teller distortion by the application of magnetic field.Comment: 4 Pages, 4 Figure

Airglow emissions : fundamentals of theory and experiment

In this article, discovery of airglow and ionosphere has been discussed briefly in the historical and scientific perspectives. Mentioning about all significant atmospheric parameters, different areas of research in airglow and different ionospheric layers of importance have been briefly described. Different types of airglow emissions, related chemical kinetics, different excitation mechanisms of the involved atomic, molecular or ionic species have been discussed giving stress specially to four main airglow emissions. Different layers of ionosphere, their characteristic material content and specific ranges of responses to different kinds of interacting fields etc. have also been briefly discussesd. The Sun has been described as the main source of all kinds of energetic interactions with the terrestrial ionosphere. Specific solar parameters, that are representatives of various solar activity, have been discussed briefly in relation with the corresponding covariation of various ionospheric parameters involved in the calculations of airglow intensity. Different solar activity periodicities that have been discovered upto date are mentioned. Relations of different airglow emissions with ionospheric activities and specific ionospheric parameters have been briefly described. The important role of ozone in the stratosphere and lower thermosphere in the production of some airglow emissions has been discussed with exemplary works. Different wellknown features of airglow intensity variations such as altitudinal variation, latitudinal variation etc have also been mentioned. Different atmospheric models have been briefly described along with their usefulness. Descriptions of different missions and campaigns with which a number of airglow experiment sets are involved , have been presented in a tabular form. Discovery of some new airglow lines, some newly proposed excitation mechanisms and related kinetics, and some remeasured or reevaluated constants and coefficients have been reported too. Effect of different types of solar activity, of different kinds of lunar influences and of various terrestrial atmospheric features, such as, geomagnetic field alignment, geomagnetic storm, lightning, earthquake, dynamical coupling between layers of thermosphere, E x B drift and ring current etc on terrestrial airglow emissions have also been briefly discussed. Some interesting airglow related features which have been discovered in recent past are discussed. Applications of different airglow features have been reported. Lastly, facts and speculation about ionospheric compositions, activities and possible airglow emission features of other inner and outer planets, satellites, comets and meteors have been discussed very briefly.Author Affiliation: R Chattopadhyay and S K Midya 1.Haripal G.D. Institution, Khamarchandi, Hooghly-712 405, West Bengal, India 2.Department of Physics, Serampore College, Serampore, Hooghly-712 201, West Bengal, India 3.Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata-700 084, India E-mail : [email protected] G.D. Institution, Khamarchandi, Hooghly-712 405, West Bengal, India 2Department of Physics, Serampore College, Serampore, Hooghly-712 201, West Bengal, India 3Centre for Space Physics, 43 Chalantika, Garia Station Road, Kolkata-700 084, Indi

Anomalous thermal expansion of Sb2_2Te3_3 topological insulator

We have investigated the temperature dependence of the linear thermal expansion along the hexagonal c axis ($\Delta L$), in-plane resistivity ($\rho$), and specific heat ($C_p$) of the topological insulator Sb$_2$Te$_3$ single crystal. $\Delta L$ exhibits a clear anomaly in the temperature region 204-236 K. The coefficient of linear thermal expansion $\alpha$ decreases rapidly above 204 K, passes through a deep minimum at around 225 K and then increases abruptly in the region 225-236 K. $\alpha$ is negative in the interval 221-228 K. The temperature dependence of both $\alpha$ and $C_p$ can be described well by the Debye model from 2 to 290 K, excluding the region around the anomaly in $\alpha$

Exact quantization of a PT-symmetric (reversible) Li\'enard-type nonlinear oscillator

We carry out an exact quantization of a PT symmetric (reversible) Li\'{e}nard type one dimensional nonlinear oscillator both semiclassically and quantum mechanically. The associated time independent classical Hamiltonian is of non-standard type and is invariant under a combined coordinate reflection and time reversal transformation. We use von Roos symmetric ordering procedure to write down the appropriate quantum Hamiltonian. While the quantum problem cannot be tackled in coordinate space, we show how the problem can be successfully solved in momentum space by solving the underlying Schr\"{o}dinger equation therein. We obtain explicitly the eigenvalues and eigenfunctions (in momentum space) and deduce the remarkable result that the spectrum agrees exactly with that of the linear harmonic oscillator, which is also confirmed by a semiclassical modified Bohr-Sommerfeld quantization rule, while the eigenfunctions are completely different.Comment: 10 pages, 1 figure, Fast Track Communicatio

A conjecture on Exceptional Orthogonal Polynomials

Exceptional orthogonal polynomial systems (X-OPS) arise as eigenfunctions of Sturm-Liouville problems and generalize in this sense the classical families of Hermite, Laguerre and Jacobi. They also generalize the family of CPRS orthogonal polynomials. We formulate the following conjecture: every exceptional orthogonal polynomial system is related to a classical system by a Darboux-Crum transformation. We give a proof of this conjecture for codimension 2 exceptional orthogonal polynomials (X2-OPs). As a by-product of this analysis, we prove a Bochner-type theorem classifying all possible X2-OPS. The classification includes all cases known to date plus some new examples of X2-Laguerre and X2-Jacobi polynomials