Zero Temperature Insulator-Metal Transition in Doped Manganites

We study the transition at T=0 from a ferromagnetic insulating to a ferromagnetic metallic phase in manganites as a function of hole doping using an effective low-energy model Hamiltonian proposed by us recently. The model incorporates the quantum nature of the dynamic Jahn-Teller(JT) phonons strongly coupled to orbitally degenerate electrons as well as strong Coulomb correlation effects and leads naturally to the coexistence of localized (JT polaronic) and band-like electronic states. We study the insulator-metal transition as a function of doping as well as of the correlation strength U and JT gain in energy E_{JT}, and find, for realistic values of parameters, a ground state phase diagram in agreement with experiments. We also discuss how several other features of manganites as well as differences in behaviour among manganites can be understood in terms of our model.Comment: To be published in Europhysics Letter

Malpe fishing harbour inferno: an impact analysis

An unprecedented fire disaster, in which 196 mechanised fishing boats were gutted, took place at Malpe, a major fishing harbour in Karnataka State in the afternoon of 19th July, 1979. The total loss due to this havoc has been estimated at 2.3 crores of rupees. Though the total loss to the nation on accountof the fire disaster is to the tune of Rs. 2.3 crores, the individual loss of the owners of mechanised vessels was much less. A member of C. M. F. R. I. staff has been deployed to gather information relating to the progress made towards the normalisation of fishing activities in the affected area. This would enable monitoring of the process of rehabilitation in the coming month

Sodium vacancy ordering and the co-existence of localized spins and itinerant charges in NaxCoO2

The sodium cobaltate family (NaxCoO2) is unique among transition metal oxides because the Co sits on a triangular lattice and its valence can be tuned over a wide range by varying the Na concentration x. Up to now detailed modeling of the rich phenomenology (which ranges from unconventional superconductivity to enhanced thermopower) has been hampered by the difficulty of controlling pure phases. We discovered that certain Na concentrations are specially stable and are associated with superlattice ordering of the Na clusters. This leads naturally to a picture of co-existence of localized spins and itinerant charge carriers. For x = 0.84 we found a remarkably small Fermi energy of 87 K. Our picture brings coherence to a variety of measurements ranging from NMR to optical to thermal transport. Our results also allow us to take the first step towards modeling the mysterious ``Curie-Weiss'' metal state at x = 0.71. We suggest the local moments may form a quantum spin liquid state and we propose experimental test of our hypothesis.Comment: 16 pages, 5 figure

Theory of Insulator Metal Transition and Colossal Magnetoresistance in Doped Manganites

The persistent proximity of insulating and metallic phases, a puzzling characterestic of manganites, is argued to arise from the self organization of the twofold degenerate e_g orbitals of Mn into localized Jahn-Teller(JT) polaronic levels and broad band states due to the large electron - JT phonon coupling present in them. We describe a new two band model with strong correlations and a dynamical mean-field theory calculation of equilibrium and transport properties. These explain the insulator metal transition and colossal magnetoresistance quantitatively, as well as other consequences of two state coexistence

Role of Lashuna Rasayana in Margavaranaja Pakshagahta - A Case Study

The health of an individual is accessed by the optimum structural and functional wellbeing. The functional ability of the body may be physiological or physical is attributed to Vata. In morbidity, the same Vatadosha will affect the functionality, in terms of motor or sensory functions. The wide spectrum of disorders due to morbid Vatadosha is put under the heading of Vatavyadhi. Depending upon the affected part of the body further it is categorized as, Ekangavata, Sarvangavata and Pakshaghata. In Pakshaghata Chestanivrutti of one half of the body either left or right may be observed.[1] Pakshghata is one among 80 Nanatmaja Vyadhi.[2] There are three distinct Nidana for Pakshaghata. Dhatukshayaja, Margavarana and Swakopa.[3] Margavarana refers to the obstruction of the Raktamarga. Prime causative factors for Margavarana is Santarpanajanya Nidana leads to Dhamani Pratichyaya ends up in Pakshaghata. In modern science it is better understood as stroke syndrome. Lashunsa Rasayana4 is considered to be best in case of Vata Vyadhi. It is even indicated in Pakshaghata. In the present study role of Lashunsa Rasayana is done on the patients suffering from Margavaranaja Pakshaghata

Colossal magnetoresistance manganites: a new approach

Manganites of the LA1-x Ca xMnO3 family show a variety of new and poorly understood electronic, magnetic and structural effects. Here we outline a new approach recently proposed by us, where we argue that due to strong Jahn-Teller (JT) coupling with phonons the twofold degenerate eg states at the Mn sites dynamically reorganize themselves into localised, JT polaronsl with exponentially small inter-site hopping, and band-like, nonpolaronic statesb, leading to anew 2-band model for manganites which includes strong Coulomb and Hund's couplings. We also discuss some results from a dynamical mean-field theory treatment of the model which explains quantitatively a wide variety of experimental results, including insulator-metal transitions and CMR, in terms of the influence of physical conditions on the relative energies and occupation of thel andb states. We argue that this microscopic coexistence of the two types of electronic states, and their relative occupation and spatial correlation is the key to manganite physics

COVID-19 and tuberculosis in South Africa: A dangerous combination

There has been much speculation during the past week about the catastrophe that awaits once coronavirus disease 2019 (COVID-19) establishes itself in the poorest communities of South Africa (SA) and, importantly, in informal settlements. Evidence to date suggests that COVID-19 is efficiently passed from infected individuals via large droplets and hard-surface fomites