Debashis Mondal worked within NFFA-Trieste as CNR-IOM Postdoc from 2018 to February 2021.
Debashis Mondal postdoctoral activity was focused on the electronic structure of topological insulators and related low dimensional materials, such as transition metal (di)chalcogenides, Weyl semimetals etc. The main tools used in his study were ARPES, spin-resolved ARPES and STM techniques.
Chiral crystal YbNi3Ga9 is known as an intermediate valence compound in which a strong hybridization between the 4f orbitals and the conduction band is present. The Co-substitution to YbNi3Ga9 works as a hole doping that reduces the Kondo temperature and enhances the effective mass of itinerant charge carriers. Using angle-resolved photoelectron spectroscopy, the complex band structure of Yb(Ni1−xCox)3Ga9 (x=0,0.1) is revealed. A Yb2+ 4f7/2 band and evidences of hybridization to valence bands are found near the Fermi level. Both YbNi3Ga9 and the Co-substituted compound exhibit double hexagonal Fermi surfaces centered at the Γ¯-point, surrounded by a large snowflake-like surface, and a triangular electron-like surface along the Γ¯M¯ direction. By changing the incident photon energy, the band dispersion along the c-axis and the barrel-shaped Fermi surface is observed.
From our users
Phys. Rev. B, 100, 195134, (2019)
Observation of bulk states and spin-polarized topological surface states in transitionmetal dichalcogenide Dirac semimetal candidate NiTe2
B. Ghosh, D. Mondal, C.-N. Kuo, C.S. Lue, J. Nayak, J. Fujii, I. Vobornik, A. Politano, and A. Agarwal
We predict NiTe2 to be a type-II Dirac semimetal based on ab initio calculations and explore its bulk and spin-polarized surface states using spin- and angle-resolved photoemission spectroscopy (spin-ARPES). Our results show that, unlike PtTe2, PtSe2, and PdTe2, the Dirac node in NiTe2 is located in close vicinity to the Fermi energy. Additionally, NiTe2 also hosts a pair of band inversions below the Fermi level along the Γ−A high-symmetry direction, with one of them leading to a Dirac cone in the surface states. The bulk Dirac nodes and the ladder of band inversions in NiTe2 support unique topological surface states with chiral spin texture over a wide range of energies. Our work paves the way for the exploitation of the low-energy type-II Dirac fermions in NiTe2 in the fields of spintronics, infrared plasmonics, and ultrafast optoelectronics.
From our users
Phys. Rev. B, 100, 121104, (2019)
Surface states and Rashba-type spin polarization in antiferromagnetic MnBi2Te4(0001)
R.C. Vidal, H. Bentmann, T.R.F. Peixoto, A. Zeugner, S. Moser, C.-H. Min, S. Schatz, K. Kißner, M. Ünzelmann, C.I. Fornari, H.B. Vasili, M. Valvidares, K. Sakamoto, D. Mondal, J. Fujii, I. Vobornik, S. Jung, C. Cacho, T.K. Kim, R.J. Koch, C. Jozwiak, A. Bostwick, J.D. Denlinger, E. Rotenberg, J. Buck, M. Hoesch, F. Diekmann, S. Rohlf, M. Kalläne, K. Rossnagel, M.M. Otrokov, E.V. Chulkov, M. Ruck, A. Isaeva, and F. Reinert
The layered van der Waals antiferromagnet MnBi2Te4 has been predicted to combine the band ordering of archetypical topological insulators such as Bi2Te3 with the magnetism of Mn, making this material a viable candidate for the realization of various magnetic topological states. We have systematically investigated the surface electronic structure of MnBi2Te4(0001) single crystals by use of spin- and angle-resolved photoelectron spectroscopy experiments. In line with theoretical predictions, the results reveal a surface state in the bulk band gap and they provide evidence for the influence of exchange interaction and spin-orbit coupling on the surface electronic structure.
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