Prof. INDRA DASGUPTA

School of Physical Sciences

Indian Association for the Cultivation of Science

Jadavpur, Kolkata 700 032

E-mail: sspid[at]iacs.res.in

Brief Bio-sketch:

Prof. Indra Dasgupta has obtained his Master's degree in Physics from IIT Kanpur and PhD degree from Calcutta University based on a work done at S.N. Bose National Centre for Basic Sciences on the topic Electronic Structure and Transport in Quantum Disordered Solids. He subsequently worked at the Max Planck Institute for Solid State Research in Stuttgart, Germany, IIT Bombay, IIT Kharagpur before joining Indian Association for the Cultivation of Science (IACS), Jadavpur, Kolkata. He is presently Dean Academic Administration and R&D and Senior Professor at the School of Physical Sciences in IACS, Kolkata. His research interests are electronic structure calculations of novel magnetic systems, strongly correlated systems, low-dimensional quantum spin systems, magnetic properties of materials at nano scale and disordered systems.

Electronic Structure of coupled quantum dots and rods: Novel heterostuctures at nano-scale

We shall present our results on first-principles electronic structure calculations of recently synthesized II-VI coupled quantum dots [1] and III-V quantum rods [2] which are novel heterostructures at nano-scale. A novel method based on energy resolved charge density is employed to calculate the band offsets which naturally take into account the impact of quantum confinement on the band-offsets of these heterostructures at nanoscale[3]. We show that the offsets of highest occupied molecular orbitals (HOMO) as well as the lowest unoccupied molecular orbitals (LUMO) can be tuned by changing the sizes of the components of the coupled quantum dots and rods thereby providing an additional control parameter to tune the band gap and the optical properties[4]. Our investigations also suggest that formation of alloy near the interface has very little influence on the band offsets, although it affects the spatial localization of the quantum states from the individual components. The strain profiles for coupled quantum dots and rods are calculated using a multiscale approach where the parameters for an atomistic model for elasticity are calculated using ab initio electronic structure calculations. Comparing the influence of strain on coupled quantum dots and core/shell nanowires, we find strain practically has no role in the electronic structure of coupled quantum dots as the small effective area of the interface in a coupled quantum dot helps a large part of the structure remain free from any substantial strain. Finally we have calculated the transport properties for a representative CdS-ZnSe coupled dot and show that it displays asymmetric I-V characteristics with high rectification ratio and therefore may offer an alternative to conventional molecular electronics [5].

References:

[1].S. Sengupta, N. Ganguli, I. Dasgupta, D.D. Sarma, and S. Acharya, Advanced Materials, 23 1998, (2011);
[2] J.K. Panda, A. Roy, A. Chakraborty, I. Dasgupta . E. Hasanu , D. Ercolani, L. Sorba and M Gemmi Phys Rev B 92, 205302 (2015);
[3] N. Ganguli, S. Acharya and I. Dasgupta, Phys. Rev. B 89, 245423 , (2014) ;
[4] A. Dalui, A. Chakraborty, U Thupakula, A Hossain Khan, S. Sengupta, B Satpati , D D Sarma , I. Dasgupta and S Acharya, J. Phys Chem C 120 10118 (2016);
[5] Simon Liebing, Torsten Hahn, Jens Kortus, B. Das, A. Chakraborty, and I. Dasgupta (Submitted for Publication) (2019)