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The evolution of the theory of high temperature superconductors (HTS) and understanding of their dynamical behaviour became one of the foremost leading challenges, and the quest is still on. The unit cell of HTS incorporates a large number of atoms or ions, increasing the possibility of many-body interactions [1,2]. Furthermore, dimensionality plays a significant role in the mechanism of high temperature superconductivity (HTSC), which drew the attention of many experimentalists and theorists to study the mechanism of HTS.
Many studies reported that the phonons exhibit a central role in characterizing the several dynamical properties of HTS, which need to be studied to a satisfactory extent. The careful investigation of anharmonicity is also complicated from a theoretical perspective because an anharmonic disturbance is considerably significant at very low temperature. The role of doping (impurity) in HTS play a crucial part to control the superconducting properties of copper oxide crystals. Moreover, the influences of disorders and defects can be thoroughly understood, which extremely modify the frequency (energy) spectrum and dynamical characteristics of crystals. The electron-phonon (ep) coupling is another prominent effect for describing the features of HTS. However, the role of electrons and phonons appear to be relevant during the formation of pairons (or Cooper pair) in the transition region instead of heat transport. The epinteractions in HTS display phononic as well as electronic characteristics via the density of states. Indeed, the density of states plays a significant role in studying a large number of dynamical properties; especially, the electronic and phononic heat capacities, thermal transport, etc., of HTS.
In light of the above discussions, I will present the theoretical development of renormalized phonon frequency spectrum, the density of states of phonons and electrons, and the heat capacity of phonons and electrons for high temperature superconductors in a new framework adopting the many-body Green’s function theory of phonons and electrons via model Hamiltonian considering the effect of anharmonicities, defects, ep-interactions and Born-Mayer-Huggins potential. This theoretical approach extraordinarily separates the phonon density of states and phononic heat capacity into diagonal and non-diagonal components, which chiefly depends on mass change parameter. The theoretically developed results were applied to La2-xSrxCuO4 and YBa2Cu3O7-δ superconductors for successful numerical estimation [3,4,5]. These investigations reported that the effects of anharmonicities, point impurities, and electron-phonon interactions are essential and suitable for the investigations of dynamical properties of HTS. In the talk, I will present detailed information and a description of my research work.
References:
[1] Anushri Gupta, SK Verma, A Kumari, BD Indu, Journal of Physics and Chemistry of Solids, 134, 83-88, (2019).
[2] Anushri Gupta, A Kumari, SK Verma, BD Indu, Physica C: Superconductivity and its Applications, 551, 55-65 (2018).
[3] Anushri Gupta, SK Verma, A Kumari, BD Indu, Journal of Superconductivity and Novel Magnetism, 33, 2293–2297 (2020).
[4] Anushri Gupta, SK Verma, A Kumari, BD Indu, International Journal of Modern Physics B, 33, 1950328, (2019).
[5] Anushri Gupta, SK Verma, A Kumari, BD Indu, International Journal of Modern Physics B, 32, 1850237, (2018).
Dr. Anushri Gupta is a theoretical Condensed Matter Physicist. She works on a wide variety of problems of High Temperature Superconductors in the area of Condensed Matter Physics dealing with the quantum dynamical many-body theory of Green’s function via model Hamiltonian consisting of many-body interactions viz. harmonic phonons and electrons, their interactions, anharmonicities and defects.
Dr. Gupta has an excellent academic career right from the school to university level. She passed all her examinations in first division. She has been holder of the National Fellowship “Ministry of Human Resource Development (MHRD)” JRF & SRF fellowships for her studies and for her research work. She obtained her Doctoral Degree from the prestigious Indian Institute of Technology Roorkee (IITR) in October 2019 for her work on “Dynamical Properties of High Temperature Superconductors”.
She published over 10 research papers in refereed Journals and 5 international conference proceedings, attended International/ National conferences, workshops, symposiums and presented research papers. She has received financial support from “Science and Engineering Research Board (SERB), Government of India” to present her research paper in international conference at Italy. She was a member of American Physical Society (APS) and Institute of Electrical and Electronics Engineers (IEEE) during her Ph.D. program.
Also, she has participated in the academic activities and administrative responsibilities at the Department of Physics of IITR.