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  • 2:27 PM, Sunday, 26 Sep 2021

Department of Physics
S. Murugesh, Ph.D.


  • Assistant Professor in Dept. of Physics & Meteo., IIT-Kharagpur (2007-2009).
  • Scientist, CNLD, Bharathidasan University, Trichy (Jan’ 2007-Aug’ 2007).
  • Research Associate, School of Mathematics, UNSW, Sydney, Australia (2005-2006).
  • Research Associate, CNLD, Bharathidasan University, Trichy (2002-2004).
  • JRF, IMSc, Chennai (1996-2002).

Research Work / Area
  • Nonlinear Dynamics & applications to condensed matter systems, Geometry & integrability, Solitons in condensed matter physics

Welcome to the webpage of the Computational Physics lab. The course consists of a set of programming exercises, mostly drawn from typical problems you come across in physics. The programs have to be written in C (which you are expected to learn by yourself). The reports for each of the exercises are to be submitted as a PDF document written using latex-2e (which, again, will not be taught). The set of exercises and some help pages are given below:


Help with Linux, Latex, C and gnuplot

Report template

PS: The report template above is actually a .tex file masquerading as a .pdf file.

Change file name from sc11Bxxx.pdf to sc11Bxxx.tex after downloading.

Content, and other information, such as lecture notes (including a couple of old ones), assignments, schedule, etc., for courses I offer(ed) can be found here.

Current: Physics-2 (PH121), Jan-June 2019

This is a course on Electricity and Magnetism, in its local form, leading to Electrodynamics. The course starts with an introduction of Differential and Integral Calculus, and ends with a summary of Maxwell's equations.


Assignment 1: Due - 11 February

Some earlier Question papers

From 2017: Quiz 1, Quiz 2, EndSem

A few other lecture notes:


2.Computational Physics

3.Quantum Mechanics (partial)

My primary interests are in Theory of Solitons, Geometry and Integrable systems with applications in Condensed Matter Physics, especially in classical spin systems, falling under the broader area of Nonlinear Dynamics. Our interest is largely around studying spin behavior in Nanoscale Ferromagnets in the context of spin transfer torque induced spin reversal, with application in magnetic recording media.



A soliton surface corresponding to a fluid vortex

A soliton surface associated with a (one-soliton) fluid vortex filament

Recently we discovered knot soliton solution to the Non-linear Schrödinger equation (NLSE). The NLSE arises a good approximation in various physical systems: describing the propogation of light in non-linear media, vortex filament motion in inviscid fluids, evolution of a ferromagnetic spin chain, to name a few. Under certain approximations it can also describe the wave function of a Bose Einstein condensate.  There exists a clear and exact mapping of the complex field satisfying NLSE to a moving curve in 3-D. Within fairly good limits this curve imitates the motion of a thin vortex filament in fluids or superfluids. We have recently obtained a breather soliton solution to the NLSE, whose corresponding curve in 3-D carries a knot. See 4. below for details.

As of now, we are unable to give a clear physical interpretation for the knot --- it can't be thought of as a vortex filament, as it exceeds the limits of approximations where NLSE is a good description. A possible interpretation in light propogation in non-linear media is explored.

The breather mode in a ferromagnetic spin chain carries in it an interesting topological connection. Suppose a finite spin chain in 1-D is constrained with periodic boundary conditions --- the ends can then be identified, or closed (as in figure below). Then, the breather mode on such a chain witnesses an evolution which continuously changes the twist in the chain from n --> n-2 --> n, (or, a 4π change in twist, and back) a manouevre known in various popular names --- the Dirac string trick, the belt trick, Balinese plate trick, etc. The curious aspect about the trick is that by a continous transformation, the total twist can only be changed by 4π, not 2π.  The trick is usually used as an illustration of the simple connectedness of the group SU(2), and its period 4π.   

Recent Publications
  1. Spin-transfer-torque driven magneto-logic gates using nano spin-valve pillars. C. Sanid and S. Murugesh, Jap. J. Appl. Phy. 51, 063001 (2012).
  2. Spin-Transfer-Torque driven magneto-logic OR, AND and NOT gates. C. Sanid and S. Murugesh, Euro. Phys. J. ST. 222, 711 (2013).
  3. Synchronization and chaos in spin-transfer-torque nano-oscillators coupled via a high speed Op Amp., C. Sanid and S. Murugesh, J. Phys. D: Appl. Phys. 47, 065005 (2014).
  4. Knot soliton solutions for the one-dimensional non-linear Schrödinger equation, Rahul O R and S. Murugesh, J. Phys. Commun. 2, 055033 (2018).
  5. Rogue breather modes: Topological sectors, and the `belt-trick', in a one-dimensional ferromagnetic spin chain, Rahul O R and S. Murugesh, arXiv:1807.01867

‘Coherent Structures and Patterns in Nonlinear Systems,’ Funded by DST, GOI,  under the SERC – FASTTRACK scheme (completed in 2009).