My research interest lies in a broad area of theoretical condensed matter physics with expertise in modeling material-specific properties related to topology, quantum geometry, transport, plasmons, and optical response of materials. I use density function theory (DFT) based first-principles techniques along with material-specific tight-binding methods and analytical modeling to discover, understand, and engineer material properties. I am interested in studying a variety of materials, such as two-dimensional materials, heterostructures, and various quantum materials, including magnetic materials, topological materials, Axion insulators, etc. I enjoy working in collaboration with various experimental research groups worldwide. A few highlights from various areas of my research are given below (please refer to the publication list for details).
Quantum Geometry and Transport
Berry curvature and quantum metric are the imaginary and the real part, respectively, of the complex quantum geometric tensor. The quantum metric measures the gauge-invariant “distance” between Bloch wavefunctions at different momenta, while the Berry curvature characterizes the change in the phase of Bloch wavefunction along a closed contour in the Brillouin zone. In the past few decades, the role of Berry curvature has been celebrated widely in various areas of condensed matter physics due to its connection to anomalous Hall conductivity and topological invariants. On the other hand, quantum metric-induced phenomena remained largely unexplored. In close collaboration with experiments, we have made several discoveries on Berry curvature and quantum geometry-related effects. A few selected publications are given below:
Probing quantum geometry through optical conductivity and magnetic circular dichroism,
B. Ghosh# et al., arxiv.org/abs/2401.09689 (2024) (To Review in Science Advances) [#CA] [First computation of the quantum weight]
Observation of the antiferromagnetic diode effect,
A. Gao, S. Chen, B. Ghosh, et al., (Nature Electronics (In Press))
Quantum metric nonlinear Hall effect in a topological antiferromagnetic heterostructure,
A. Gao, Y. Liu, J. Qiu, B. Ghosh et al. Science 381, 181(2023) [First demonstration of the quantum metric induced non-linear Hall effect]
Discovery of a magnetic Dirac system with large intrinsic non-linear Hall effect,
F. Mazzola*#, B. Ghosh*# et al., Nano Letters 23, 902(2023) [*EC][#CA]
Layer Hall effect in a 2D topological axion antiferromagnet, [Discovery of a new type of Hall effect]
A. Gao, Y. Liu, C. Hu, J. Qiu, C. Tzschaschel, B. Ghosh et al., Nature, 595, 521 (2021) [Highlighted by the DST and PIB Govt. of India]
Novel Optical Properties of Quantum Materials
I am interested in material-specific modeling of various novel optical properties, including natural optical activity, optical Axion coupling, gyrotropic birefringence, etc. This involves the computation of higher order susceptibility and magneto-electric coupling induced response within the Wannier function formalism by developing home-built codes. Material-specific computation of such optical response is still rare. A few highlights of my work in this area are given below.
Topological Circular Dichroism in Chiral Multifold Semimetals, [A rare example of quantized optical response]
J. Ahn#, B. Ghosh#, Physical Review Letters 131, 116603(2023) [#CA]
Extreme Optical Anisotropy in the Type-II Dirac Semimetal NiTe2 for Applications to Nanophotonics,
C. Rizza, D. Dutta, B. Ghosh et al., ACS Applied Nano Materials. 5, 18531 (2022)
Axion optical induction of antiferromagnetic order, [ Demonstration of optical control of AFM order]
J. Qiu, C. Tzschaschel, J. Ahn, A. Gao, H. Li, X. Zhang, B. Ghosh et .al, Nature Materials 22, 583 (2023)
Plasmons in Quantum Materials
Plasmons are collective density oscillations that are of enormous importance for designing next-generation optoelectronics devices. The existing open-source codes that are suitable for exploring plasmons using first-principles calculations (for example, GPAW) do not include the effect of spin-orbit coupling, which is a crucial ingredient for studying quantum materials. This has motivated us to develop in-house codes for computing plasmons using Wannier function-based modeling, thus broadening the scope of material-specific study of plasmons. A few highlights of our work in this area include:
Collective plasmonic modes in the chiral multifold fermionic material CoSi,
D. Dutta*, B. Ghosh*#, et al., Physical Review B 105, 165104 (2022) [*EC][#CA]
Broadband excitation spectrum of bulk crystals and thin layers of PtTe2,
B. Ghosh et al., Physical Review B 99, 045414 (2019)
3D Dirac Plasmons in the Type-II Dirac Semimetal PtTe2, [Experimental discovery of the 3D Dirac plasmon]
A. Politano, G. Chiarello, B. Ghosh, et al., Physical Review Letters 121, 086804 (2018) [Editor’s choice and Featured in physics article]
Anisotropic plasmons, excitons, and electron energy loss spectroscopy of phosphorene,
B. Ghosh, P. Kumar, A. Thakur et.al, Physical Review B 96, 035422 (2017).
Materials Discovery and Characterization
Using high-throughput computational methods, I built an in-house band structure database of ~12500 unique non-magnetic compounds listed in the Pearson Crystal Database. Using this database, we have predicted several new topological materials and stable two-dimensional materials for the first time. Additionally, in close collaboration with angle-resolved photoemission spectroscopy (ARPES) experiments, I have helped characterize a number of new topological materials. A few highlights of our study in this area are given below:
Mitrofanovite Pt3Te4: A Topological Metal with Termination-Dependent Surface Band Structure and Strong Spin Polarization,
J. Fujii*, B. Ghosh*, Ivana Vobornik* et.al, ACS Nano, 15, 14786 (2021)[*EC]
Realization of an intrinsic ferromagnetic topological state in MnBi8Te13, [Discovery of an intrinsic FM topological state]
C. Hu, L. Ding, K. N. Gordon, B. Ghosh et al., Science Advances 6, eaba4275 (2020)
K2CoS2: A new two-dimensional in-plane antiferromagnetic insulator,
A. B. Sarkar, B. Ghosh, B. Singh et al., Physical Review B 102, 035420 (2020)
Saddle-point Van Hove singularity and dual topological state in Pt2HgSe3,
B. Ghosh et al., Physical Review B 100, 235101 (2019)
Observation of bulk states and spin-polarized topological surface states in transition metal dichalcogenide Dirac semimetal candidate NiTe2,
B. Ghosh*, D. Mondal* et al., Physical Review B 100, 195134 (2019) [*EC]
SnP3: A Previously Unexplored Two-Dimensional Material,
B. Ghosh*, S. Puri* et al., The Journal of Physical Chemistry C 122, 18185 (2018) [*EC] [Prediction of a stable new 2D material]
Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag2BiO3, [First example of a 3D Hourglass Dirac semimetal]
B. Singh*, B. Ghosh* et al., Physical Review Letters 121, 226401 (2018) [*EC]
Engineering Material Properties
Engineering properties of materials to improve their potential for real-world application is highly desired. Two-dimensional materials offer exciting possibilities in this regard. Through heterostructure engineering, chemical doping, and the use of external stimuli like electric field, strain, etc., the electronic properties of a 2D material can be manipulated to a great extent. A few selected studies of our work in this direction are given below.
Tunable spin polarization and electronic structure of bottom-up synthesized MoSi2N4 materials,
R. Islam*, B. Ghosh* et al, Physical Review B 104, L201112(2021) [*EC]
Topological states in superlattices of HgTe-class materials for engineering three-dimensional flat bands,
R. Islam, B. Ghosh et al., Physical Review Research 4, 023114(2022)
Electric-field tunable Dirac semimetal state in phosphorene thin films,
B. Ghosh et al., Physical Review B 94, 205426 (2016)
First-principles cluster expansion study of functionalization of black phosphorene via fluorination and oxidation,
S. Nahas, B. Ghosh, et al. Physical Review B 93, 165413 (2016)
Electric field-induced gap modification in ultrathin blue phosphorus,
B. Ghosh et al., Physical Review B 91, 115433 (2015)
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