Kolloquiumsvortrag: Dr. Sanjeev Kumar Srivastava, Indian Institute of Technology, Kharagpur, India / 23.11.15

23.11.2015 von 17:15 bis 18:45

Institut für Materialwissenschaften, Kaiserstr. 2, 24143 Kiel, Geb. D, Raum: "Aquarium

Titel:  Microscopic and macroscopic studies of electron correlations in solids

 

Abstract:

Electron correlations determine or influence almost all aspects of solid state properties, be it electrical transport, magnetic and superconducting properties, or even more complex strong electron correlation based phenomena. The study of electron correlations, thus, occupies a key position in the central theme of current experimental and theoretical research in condensed matter physics. There are two basic ways to investigate electron correlations: (i) studies of macroscopic properties, which basically constitute a report on the ensemble- and time-averaged behaviour of the solid, and (ii) microscopic investigations, which essentially provide an explanation to the macroscopic behaviour. The microscopic measurements are performed at very short length (~ 1 - 10 nm) and time (fs - ns) scales. An extremely useful microscopic technique is the observation of perturbation, produced by the interactions between the crystal electromagnetic fields and nuclear electromagnetic moments, of the angular anisotropic distribution of the intensity of γ-rays emitted by a radioactive nucleus produced in a heavy ion induced fusion evaporation reaction and subsequently implanted into the solid. The technique is known as Time-Differential Perturbed Angular Distribution (TDPAD). It is further desirable always to compliment the experimental results with first-principles density functional theory (DFT).

 

This talk will begin with short descriptions of the basic principles of the microscopic TDPAD technique and the DFT. Subsequently, a brief overview of the following electron correlation based representative results will be presented: (i) spin fluctuations of Fe in dilute Pd alloys [1], (ii) defect induced magnetism in HOPG [2], (iii) Fe hyperfine field in the pnictide superconductor CaFe2As2 [3], and (iv) 3d impurities in Cr [4]. In addition, a recent macroscopic study on quantum phase transitions in Pd-Ni nanoalloys [5] will also be discussed.

References:

1.  S.K. Srivastava,S.N. Mishra and G.P. Das,J. Phys.: Cond. Matter 18 (2006) 9463.

2.  S.K. Mohanta, S.N. Mishra, S.M. Davane, and S.K. Srivastava, J. Phys.: Cond. Matter 24 (2012) 085601.

3.  S.K. Mohanta, S.N. Mishra, S.M. Davane,  N. Kumar, A. Thamizhavel, S. Layek, Z. Hussain and S.K. Srivastava, Nucl. Instr. Meth. Phys. Res. B 299 (2013) 71.

4.  S.N. Mishra and S.K. Srivastava, J. Phys.: Cond. Matter 20 (2008) 285204.

P. Swain, S.K. Srivastava and S.K. Srivastava, Phys. Rev. B 91 (2015) 045401.


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