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Research Interest
Research Interest
Bose-Einstein Condensate, BCS-BEC Crossover, Integrable Models and Solitons, Strongly Correlated Systems
Bose-Einstein Condensate, BCS-BEC Crossover, Integrable Models and Solitons, Strongly Correlated Systems
Research Description
Research Description
The cold atom group at BU is involved in understanding the dynamics of atoms, both bosonic and fermionic, near absolute zero at the mean-field level.
The manifestation of ultra-low temperature on the atoms are quite different based on its atomic species (i.e., bosonic or fermionic) due to the existence of Pauli exclusion principle. Below a critical temperature the bosonic atoms undergo Bose-Einstein Condensation (BEC) where all the bosons are at a single energy state and behave like a single particle. It is a superfluid phase of the bosonic atoms. Similarly, a fermionic condensate is a superfluid phase formed by fermionic particles at low temperatures. The earliest recognized fermionic condensate described the state of electrons in a superconductor.
In 1995 onward, with the advent of BEC in alkali gases, the cold-atom research has progressed in leaps and bounds. Currently, ultra-cold atomic gases are the biggest testing ground for condensed matter research. However, the novelty of the subject is its wide-ranging applicability from condensed matter to quantum optics, from spintronics to quantum computation and from neutron star to sonic black-holes.
Here, at BU we are currently involved in (i) understanding the effect of laser light on the atomic condensate which sheds light on the issue of light matter interaction. (ii) Effect of disorder on entanglement when bosons are placed in double well potential. (iii) Possibility of solitary wave generation in an atomic condensate in the framework which is beyond the purview of mean-field theory.
ResearcherID: H-7950-2014
Scopus: 55259809300
Vidwan-ID: 303593
ORCiD: 0000-0002-7577-3214
Members
Members
Graduate Student
Mr. Shivam Singh
Research Area: Beyond Mean-field Analysis of Gross-Pitaevskii Equation
ANRF JRF
Mr. Ibrar
Research Area: Quantum Phases of Matter
CSIR JRF
Mr. Suhail Rashid
Research Area: Aspects of supersolid phase
Former Member
Dr. Argha Debnath, Ph. D Scholar
Current Status: Post Doctoral Fellow, HRI, Prayagraj
Mr. Jammu Tarun, UG Project Student
Current Status: Graduate student, Universität zu Köln, Germany
Ms. Aditi Chauhan, UG Project Student
Current Status: Graduate Student, University of Cardiff, UK
Ms. Katha Senapati, UG Project Student
Current Status: Graduate Student, University of Padova, Italy
Ms. Sri Satwika Adusumalli, UG Project Student
Current Status: M. Tech Student, IIT Roorkee
Mr. Ramasubramanium Hariharan, B. Tech in Engineering Physics
Current Status: Analysts-AI/LLM, Innodata
Research Grant
Research Grant
Investigation of newly emerged Quantum Phases of Matter, Sole Investigator, Core Research Grant, ANRF, 2024-27, CRG/2023/001220.
Investigation of Super-solid phase in Atomic Bose-Einstein Condensate, Sole Investigator, EMR-II, CSIR-HRDG, 2023-2026, 03/1500/23/EMR-II, Ongoing.
Effect of Beyond Mean-field correction in Atomic BEC, Sole Investigator, Core Research Grant, SERB-DST, CRG/2019/000108, 2020-2023, Completed.
Ultracold Atomic Gases in Disorder, TUBITAK-BIDEP, 2012-2013, Completed.
Research Position
Research Position
PhD Position
Candidates who have qualified NET/GATE can directly write to me.
Candidates, who are yet to qualify but motivated to start Ph.D, are encouraged to write to me with a brief description of academic accomplishments. They can obtain financial assistance by registering through Bennett University Ph.D program.
Post Doctoral Positions
National Post Doctoral Fellows (NPDF) are highly encouraged to send their CV to me for postdoc positions in my group.
Research Highlights
Research Highlights
A. Debnath, J. Tarun and A. Khan, J. Phys. B 55, 025301 (202).
Signature of supersolidity in a driven cubic-quartic nonlinear Schrodinger equation
We present analytical solution, which is periodic in nature, for a driven cubic–quartic nonlinear Schrödinger equation (DCQNLSE) is placed in a bi-chromatic optical lattice. The solution indicates the creation of density wave. Since, beyond mean-field contribution in quasi one dimensional and one dimensional geometry differs on the even exponents of the nonlinearity thus we extend our analysis toward quadratic–cubic–quartic and quadratic–cubic nonlinearities as well. Later, we study the dynamics of DCQNLSE. Our study indicates the existence of stripe phase along with considerable phase coherence. These findings allow us to comment on the possible emergence of supersolid phase in a condensate.
A. Debnath and A. Khan, Ann. Phys. (Berlin) 533, 2000549 (2021).
Investigation of Quantum Liquid: An Analytical Approach
Recent experimental observation of droplet formation in Bose-Einstein Condensate (BEC) motivates this theoretical investigation on emergence of liquid-like state in a quasi-one-dimensional BEC. These quantum droplets are stabilized by the competition between effective mean-field and beyond mean-field interaction. Analytical solutions from the governing dynamical equation is obtained. Based on their stability, the parameter regime for droplet formation is identified.
A. Debnath and A. Khan, Eur. Phys. J. D 74, 184 (2020).
On solving cubic-quartic nonlinear Schrödinger equation in a cnoidal trap
The recent observations of quantum droplet in ultra-cold atomic gases have opened up new avenues of fundamental research. The competition between mean-field and beyond mean-field interactions, in ultra-cold dilute alkali gases, is believed to be instrumental in stabilizing the droplets. This new understanding has motivated us to investigate the analytical solutions of a trapped cubic-quartic nonlinear Schrödinger equation (CQNLSE).
A. Khan and P. K. Panigrahi, J. Phys. B 46, 115302 (2013)
Bell Soliton in Ultra-cold Atomic Fermi Gas
We demonstrate the existence of supersonic bell soliton in the BCS-BEC crossover regime. Starting from the extended Thomas-Fermi density functional theory of superfluid order parameter, a density transformation is used to map the hydrodynamic mean-field equation to a Lienard type equation. As a result, bell solitons are obtained as exact solutions, which is further veri ed by the numerical solution of the dynamical equation. The stability of the soliton is established and its behavior in the entire crossover domain is obtained. It is found that, akin to the case of vortices, the bell solitons yield highest contrast in the BEC regime.
A. Khan and P. Pieri, Phys. Rev. A 80, 012303 (2009).
Ground-state fidelity in the BCS-BEC crossover
The ground-state delity has been introduced recently as a tool to investigate quantum phase transitions. Here, we apply this concept in the context of a crossover problem. Specifically, we calculate the fidelity susceptibility for the BCS ground-state wave function, when the intensity of the fermionic attraction is varied from weak to strong in an interacting Fermi system, through the BCS-Bose-Einstein Condensation crossover. Results are presented for contact and finite-range attractive potentials and for both continuum and lattice models. We conclude that the delity susceptibility can be useful also in the context of crossover problems.
A. Khan, S. Basu, S. W. Kim, J. Phys. B 45, 135302 (2012)
Effect of disorder in BCS-BEC crossover
In this paper, we have investigated the effect of weak random disorder in the BCS-BEC crossover region. The disorder is included in the mean-field formalism through NSR theory of superconducting fluctuations. A self-consistent numerical solution of the coupled equations involving the superfluid gap parameter and density as a function of the disorder strength, albeit unaffected in the BCS phase, yields a depleted order parameter in the BEC regime and an interesting nonmonotonic behaviour of the condensate fraction in the vicinity of the unitary region. The unitary regime thus demonstrates a robust paradigm of superfluidity even when the disorder is introduced. Further, we have computed the behaviour of the sound mode across the crossover that distinctly reveals a suppression of the sound velocity. We also nd the Landau critical velocity that shows similar nonmonotonicity as that of the condensate fraction data, thereby supporting a stable superfluid scenario in the unitary limit.
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