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Are There Quantum Limits to Diffusion in Quantum Many-Body Systems?

Are There Quantum Limits to Diffusion in Quantum Many-Body Systems?

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Are There Quantum Limits to Diffusion in Quantum Many-Body Systems?
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<strong>School of Physical Sciences</strong> <strong>Are There Quantum Limits to Diffusion in Quantum Many-Body Systems?</strong> Speaker: <strong>Nandan Pakhira</strong> (University of Queensland, Brisbane) Date: <strong>April 15, 2015</strong> <strong>Abstract: </strong>Good metals like copper and gold show a high optical reflectivity (shiny), electrical and thermal conductivity. Good metals are characterised by diffusive transport of coherent quasi-particle states and the resistivity (≪ milli-cm) in these materials is well within the Mott-Ioffe-Regel (MIR) limit, ha/e^2 (where a is the lattice constant). But in a wide range of strongly correlated materials and most notably in the strange metal regime of doped cuprates (high Tc superconductor) the resistivity exceeds the MIR limit and the picture of coherent quasi-particle based transport breaks down. Recent cold atom experiments [1] and theory [2] of fermions near the unitary limit suggest a lower bound for the spin diffusion constant. Sean Hartnoll, loosely motivated by holographic duality (AdS/CFT correspondence) in string theory, proposed a lower bound to the charge diffusion constant D \ge (\hbar v_F^2)/(k_B T ) in the incoherent regime of transport [3]. Using dynamical mean field theory (DMFT) we calculate the diffusion constant in the Hubbard model and explore possible existence of such bounds in the incoherent regime of transport [4]. References : 1. A. Sommer, M. Ku, G. Roati, and M. W. Zwierlein, Nature 472, 201 (2011). 2. T. Enss, and R. Haussmann, Phys. Rev. Lett. 109, 195303 (2012). 3. Sean Hartnoll, Nat. Phys. 11, 54 (2014). 4. N. Pakhira and R. H. McKenzie, Phys. Rev. B 91, 075124 (2015).

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Initially, established as a Centre for Chinese and Japanese Studies, it subsequently grew to include Korean Studies as well. At present there are eight faculty members in the Centre. Several distinguished faculty who have now retired include the late Prof. Gargi Dutt, Prof. P.A.N. Murthy, Prof. G.P. Deshpande, Dr. Nranarayan Das, Prof. R.R. Krishnan and Prof. K.V. Kesavan. Besides, Dr. Madhu Bhalla served at the Centre in Chinese Studies Programme during 1994-2006. In addition, Ms. Kamlesh Jain and Dr. M. M. Kunju served the Centre as the Documentation Officers in Chinese and Japanese Studies respectively.

The academic curriculum covers both modern and contemporary facets of East Asia as each scholar specializes in an area of his/her interest in the region. The integrated course involves two semesters of classes at the M. Phil programme and a dissertation for the M. Phil and a thesis for Ph. D programme respectively. The central objective is to impart an interdisciplinary knowledge and understanding of history, foreign policy, government and politics, society and culture and political economy of the respective areas. Students can explore new and emerging themes such as East Asian regionalism, the evolving East Asian Community, the rise of China, resurgence of Japan and the prospects for reunification of the Korean peninsula. Additionally, the Centre lays great emphasis on the building of language skills. The background of scholars includes mostly from the social science disciplines; History, Political Science, Economics, Sociology, International Relations and language.

Several students of the centre have been recipients of prestigious research fellowships awarded by Japan Foundation, Mombusho (Ministry of Education, Government of Japan), Saburo Okita Memorial Fellowship, Nippon Foundation, Korea Foundation, Nehru Memorial Fellowship, and Fellowship from the Chinese and Taiwanese Governments. Besides, students from Japan receive fellowship from the Indian Council of Cultural Relations.