Experimental Solid State Physics


Research
My current interest is primarily around exploring elementary phenomena and analogies in a couple of very old and well-studied model systems: Excitons in semiconductors and vanadium oxides.

Excitons
We study many different aspects of single and many-body aspects of hydrogen atom physics with excitons. To first approximation, the mathematical equations are the same for excitons and hydrogen atoms but due to the vastly different energy scales, what happens in astrophysical conditions can be easily observed in the lab if we substitute real hydrogen atoms with excitons.
Excitons are also technically important and part of our effort also goes into understanding specifics of light emission in semiconductors, especially the role of disorder.
[Current collaborators:
Sumi Bhuyan (PhD), Rupak Bhattacharya (PhD), Kingshuk Mukhuti (PhD), Basabendra Roy (MS), Bipul Pal (colleague).  Past collaborators--Richarj Mondal (PhD 2015)]

Phase Transition Dynamics
Another, quite unrelated, problem we are currently studying is the dynamics of first order phase transitions. These have a very rich phenomenology. Through conceptually simple but nevertheless controlled and precise experiments, we are studying various aspects of supercooling and superheating, phase coexistence, metastability and coarsening, dynamic hysteresis, noise, latent heat,... 

[Current collaborators---Tapas Bar (PhD), Satyabrata Raj (colleague); A. A. Anees (MS). Past collaborators--- K. S. Sujith (MS 2015), Arsalan Asfraf (MS 2014); Sujeet Choudhary (MS 2015)]


Experimental Techniques

With my colleague Bipul Pal, I share a spectroscopy lab. The primary technique that I use is low temperature photoluminescence spectroscopy. Biupl's expertise is in time-resolved pump probe spectroscopy of semiconductors. I have been learning this technique from him and we have developed a versatile
picosecond excitation-correlation photoluminescence set up around the femtosecond laser. We also do linear and non-linear absorption spectroscopies to study the electronic states and carrier dynamics, mostly in quantum wells and quantum dots. To get a flavour of what we do, you can have a look at this poster on Richarj's recent work.
Currently Rupak and Kinsgshuk are also working on measuring photoluminescence in magnetic fields (10 T) by integrating a homemade fibre optics arrangement and sample insert with a commercial Physical Property Measuring System (PPMS).

We have also set up a small pulsed high magnetic field facility (75 kJ) to do transport measurements up to 35 tesla. My colleagues Pradip Khatua and Uday Kumar have been very involved in various instrumentation and data processing aspects of the project.

We have also do resistivity (4K-300K), photoconductivity (4K-300K), noise measurements (77K-300K), and differential thermal analysis [latent heat] (77K-300K) measurements.

Recent Publications

Reviews

  • Self-Assembly in semiconductor epitaxy: From growth mechanisms to device applications, Bhattacharya A and Bansal B, Chapter 26 Handbook of Crystal Growth Vol. 3, 2nd Edition, Elsevier 2015, 1057–1099 Ed T. Kuech [abstract] [pdf]
  • High-field magneto-photoluminescence of semiconductor nanostructures, Hayne, M., Bansal, B., 2012, Luminescence 27, 179 [pdf] [journal]
Research Articles


  • Measurements of the electric field of zero-point optical phonons in GaAs quantum wells support the Urbach rule for zero-temperature lifetime broadening,  Bhattacharya R., Mondal R., Khatua P., Rudra A., Kapon E., Malzer S., Doehler G., Pal B., Bansal B., 2015, Physical Review Letters 114, 047402. [abstract] [pdf]  [supplementary]
  • Anti-Stokes luminescence in the light of second order perturbation theory, Bhattacharya R., Pal B., Bansal B., 2014, Applied Physics Letters 105, 191102 [pdf] [journal]
  • Anomalous effects of ultradilute impurities on heat diffusion in liquids, Ambast D.K.,  Mondal R., Pati B., Zade S.S., Bansal B., Pal B., 2015, Optics Communication 334, 184 [pdf] [journal]
  • Optical density of states in ultradilute GaAsN alloy: Coexistence of free excitons and impurity band of localized and delocalized states, Bhuyan S., Das S., Dhar S., Pal B., Bansal B., 2014, Journal of Applied Physics 116, 023103 [pdf] [journal]
  • Khatua, Bansal, and Shahar Reply [to comment on "Single-slit electron diffraction with Aharonov-Bohm phase:..."], Khatua P., Bansal, B., Shahar D., 2014, Physical Review Letters 113, 158902
  • [Comment]  [journal] [pdf]
  • Light emission despite doubly-forbidden radiative transitions in AlP/GaP quantum wells: Role of localized states, Bhuyan, S., Mondal, R., Khatua, P., Semtsiv M., Masselink, W. T., Leotin, J., Pal, B., Bansal, B., 2013, Journal of Applied Physics 114, 163101 [pdf] [journal]
  • Pauli blocking dynamics in optically excited quantum dots: A picosecond excitation-correlation spectroscopic study, Mondal, R., Bansal, B., Mandal A., Chakrabarti, S., Pal, B, 2013, Physical Review B 87, 115317 [pdf] [journal]
  • Scattering by charged dislocations in semiconductors, Bansal, B., Ghosh R., Venkataraman, V, 2013, Journal of Applied Physics 113, 163705 [pdf] [journal]
  • On conversion of luminescence into absorption and the van Roosbroeck-Shockley relation, Bhattacharya, R., Pal, B., Bansal, B., 2012, Applied Physics Letters, 100, 222103 [pdf] [journal]
  • Charge separation and temperature-induced carrier migration in Ga1-xInxNyAs1-y multiple quantum wells, Nuytten, T., Hayne, M., Bansal, B., Liu, H.Y., Hopkinson, M., Moshchalkov, V.V., 2011, Physical Review B 84, 045302 [pdf] [journal]

Teaching

Autumn 2016 Condensed Matter Laboratory

Spring 2016 : Basic Statistical Mechanics
Autumn 2015: Condensed Matter Laboratory
Spring 2015  : Basic Statistical Mechanics
Autumn 2014: First year Physics Laboratory
Spring 2014  : Physics Laboratory II; Advanced Experimental Laboratory
Autumn 2013: Physics III (Oscillations, Waves, and Optics)



      

       
        Bhavtosh Bansal

         Associate Professor,
       Department of Physical Sciences,
       Indian Institute of Science Education and Research Kolkata,
       Nadia 741246, West Bengal, INDIA.
      
        Email: bhavtosh iiserkol ac in
        Phone: +91 (0)33 66340000 ext. 1289
    
 
       [Note: Currently there are no PhD or Project openings.]
   

Updated: March 2016