Research Projects

The discovery of magnetism in two-dimensional materials has opened up new possibilities for exploring strongly correlated phenomena in reduced dimensions. NiPS₃, a layered antiferromagnetic Mott insulator, stands out as a promising system to investigate spin-phonon interactions, magnon dynamics, and coupling between spin and charge carriers, owing to its zigzag magnetic structure and pronounced electron correlation effects. This project proposes a comprehensive investigation of few-layer graphene/NiPS₃ heterostructures using Raman spectroscopy at cryogenic temperatures and under external magnetic fields, supported by magnetotransport and capacitance measurements. The goal is to uncover the microscopic interactions between lattice vibrations, magnons, and charge carriers in these low-dimensional systems. The study will begin with the fabrication of high-quality van der Waals heterostructures (e.g., FLG/NiPS₃ and FLG/NiPS₃/FLG) using dry transfer methods under inert conditions. Structural quality will be validated via AFM and room-temperature Raman spectroscopy. Raman experiments will be carried out from 400 K to 2.3 K using a helium-flow cryostat, focusing on the evolution of phonon modes across the Néel temperature (~150 K). Known phonon anomalies in NiPS₃, particularly in the 220–280 cm⁻¹ range, will be analyzed for signs of spin-phonon coupling. Magneto-Raman studies up to ±1 T will be used to identify Zeeman effects, field-induced symmetry breaking, and possible hybrid magnon-phonon modes. To complement the optical measurements, magnetoresistance (MR) studies will be performed on graphene/NiPS₃ devices. If electron-magnon coupling is active at the interface, negative MR or non-linear field responses are expected at low temperatures. Capacitance–voltage (C–V) measurements on FLG/NiPS₃/FLG capacitors will help probe magnetodielectric coupling, where field-dependent modulation of dielectric properties below Tₙ is anticipated due to spin-lattice interactions. Raman spectra will be fitted using Voigt or Lorentzian line shapes to extract phonon linewidths, peak positions, and magnon stiffness (D′), while spin-phonon coupling constants (λsp) will be estimated using established models. Transport and capacitance data will be analyzed through theoretical frameworks addressing magnon-assisted charge transport and spin-entropy effects. These combined studies aim to clarify coupling mechanisms in NiPS₃ heterostructures, advancing understanding of 2D magnetic interactions for spintronic and quantum applications. The project will be carried out at IACS Kolkata in the well-equipped laboratory of Prof. Subhadeep Datta, utilizing advanced infrastructure including cryogenic Raman spectroscopy setups, magneto-transport measurement systems, and nanofabrication tools. This research intends to generate high-impact publications and reinforce India’s emerging role as a key contributor to global research in quantum materials.