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Quantum
Condensed Matter |
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The bizarre behavior of Quantum mechanics
on macroscopic scales fascinating physicists for almost a century after the
discovery of superconductivity by Kammerlingh Onnes in 1911.The enigmatic quantum world reveals itself here
on a macroscopic scale in an peculiar condensate phase of Cooper pairs and
this condensation on the other hand effect a host of response functions and
transport properties in a non trivial way. The story did not stop there. The
discovery of Quantum Hall Effect(1980, 1982) and the
observation of Bose-Einstein condensation of cold atoms(1995), discovery of
the wonder material graphene, discovery of
topological insulato, in the last few decades
provided us one after another interesting opportunities, where we can enrich ourselves with the knowledge of
quantum phases that atomic and subatomic constituents of matter can form over
an extended range of external paramaters.
Experiments and theory have been going hand in hand in both these branches
and possible technological applications in future. Over the past few years I
have been learning about these quantum phases of ultra-cold material with my
collaborators. Here are some of my personal favourites
from present and past. Current Research Interest : 1.
Ultra Cold atoms: Ultra cold atomic systems are considered as one of the purest
quantum system where macroscopic quantum effect can be observed at
temperature close to absolute zero. A number of quantum phenomena that had
been predicted for conventional electronic solid state systems or even in the
field of particle and nuclear physics were “Quantum
Simulated” ( experimentally realized under
a highly controllable situation) in such ultra cold atomic systems.
Effect
of artificial gauge field on ultra cold supersolid: I am particularly interested in understanding the effect of
artificial gauge field (usual magnetic field and its fancier generalizations)
on the quantum phases of ultra cold atoms. Since these ultra cold atoms are
charge neutral, their orbital degrees of freedom cannot sense the real
magnetic field directly. In recent times artificial magnetic field is created
for such system through the engineering of the atom-laser interactions in
several state of the art experiments. In a set of papers with my Ph.D.
student Rashi Sachdeva we
particularly studied
the effect of such artificial gauge field on one of the most
enigmatic quantum phases known as supersolid phase
where crystalline order and superfluidity is
supposed to co-exist. Almost forty years of effort is yet to clearly confirm
the existence of supersolidity and ultra cold
atomic system is being projected as the most likely places where they can be
hunted down. In this regard we provided some interesting results showing how
the study of the effect of artificial gauge field on ultra cold atomic system
can help to identify supersolidity in such systems.
Here are the link for further reading: 1.http://pra.aps.org/abstract/PRA/v82/i6/e063617 2.http://pra.aps.org/abstract/PRA/v85/i1/e013642
3.http://arxiv.org/abs/1308.1592.
Ultra
Cold atoms in a cavity: Another system of
interest in Ultra Cold atoms which we are currently working on is the cavity
quantum electrodynamics/ cavity opto-mechanics with
such ultra cold atoms. As the name suggests, essentially this means putting
the ultra cold atoms in side a Fabry
Perot cavity and allow it a interact with selected mode(s) inside the cavity.
The cavity transmission spectrums brings rich
information about the ultra cold atomic system inside without doing a
measurement directly on the atoms. Our research goal is to propose ways that
extend the scope existing techniques of cavity QED/cavity opto-mechanics
to learn more exotic phases of ultra cold atoms. Collaboration here includes
undergraduate student (Bikash Padhi),
former M. Sc. students ( Adhip
Agarwala and Madhurima Nath), Ph.D. student ( Jasleen Lugani) and colleague ( Prof. K. Thyagarajan).
For example in a recent paper with Bikash Padhi we for the first time predicted how Shubnikov de Haas oscillation can be observed for neutral
ultra cold atoms using the tools of cavity opto-mechanics.
Here are the links for further readings on our work:1.http://prl.aps.org/abstract/PRL/v111/i4/e043603 2. http://pra.aps.org/abstract/PRA/v85/i6/e063606 2. Dirac Physics
in Condensed Matter ( Graphene): With my colleague Dr. Manish Sharma, Ph.D. student Neetu Agarwal(Garg) and research associate Sameer
Grover (currently
pursuing Ph.D. in TIFR), we have been developing a theory of ballistic
transport of electrons in mono and bilayer graphene through inhomogenous
magnetic field dubbed as magnetic barriers. Our particular achievement is
that, we systematically develop an analogy of such transport with light
propagation through a medium with varying dielectric constant. We also
predicted a number of interesting physical phenomena and there are
possibilities of novel device fabrications using our theory. A number of
interesting results is reported in a series of papers and some of these
papers are well cited. Some part of this work is supported by the SERC division
of DST Govt. of India and we recently completed a project funded by them
successfully. Here we list our papers for your
further reading on this subject. 1. http://iopscience.iop.org/0953-8984/21/29/292204/ (cited 70 times) 2.http://iopscience.iop.org/0953-8984/23/5/055501/ (cited 30 times) 3. http://iopscience.iop.org/0953-8984/24/17/175003/ 4. http://iopscience.iop.org/0965-0393/20/4/045010/
5. http://link.springer.com/article/10.1140%2Fepjb%2Fe2013-40278-9
6. http://www.worldscientific.com/doi/abs/10.1142/S0217979213410038
(invited review article). Puja Mondal
and Manisha Arora recently
joined the group as Ph.D. students and will be working primarily on
Topological Insulators and Graphene. To summarize my
current interests are: 1. Cold atomic gases (A useful site for BEC watchers) 2. Graphene (To know more
about graphene click here) 3. Ultra cold atoms in optical cavity
4. Topological Insulators. Previous Research: ( Before joining IIT Delhi)
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