The reduced electrical screening in two-dimensional materials provides an ideal platform for the realization of exotic quasiparticles, that are robust and whose functionalities can be exploited for future electronic, optoelectronic and valleytronic applications. The existence of a direct band-gap, stable excitons and trions at room temperature make two-dimensional transition metal dichalcogenides (TMDC) an ideal choice for both fundamental as well as applied research. SrTiO₃ (STO) is a functional transition metal oxide having remarkable properties such as the wide range and the tunability of dielectric constant, and rich phonon spectra with several soft phonon modes near its structural phase transition. The three body charged quasiparticle, trion, has attracted considerable attention, due to its large binding energies in TMDC, and in this work, the effects of substrate phonon interactions on the properties of trion is investigated. We found that the trion in MoS₂ is strongly interacting with soft phonon of STO. The above interaction is found to be capable of making the binding energy of trion more than 60 meV. We demonstrate selective tuning of the trion component of Photoluminance of MoS₂ by integrating it with a functional oxide substrate. Our results give clear evidence for a bound state of a soft phonon in STO and trion in MoS₂ called “polaronic trion”1.The binding energy and life time of trions were found to be tunable by modifying the phonon frequency and trion-phonon coupling.2 The implications of the selective tunability of quasiparticles in the optical emission spectra of TMDC will be discussed.
References
[1] Polaronic Trions at the MoS₂/SrTiO₃ Interface, S. Sarkar, S. Goswami, M. Trushin, S. Saha, M. Fard, S. Prakash, SJR Tan, M. Scott, K.P Loh, S. Adam*, S. Mathew*, T. Venkatesan* Adv. Mater. 31 (2019) 1903569
[2] Rotational Frohlich Coupling Creates Polaronic Trions, Maxim Trushin, Soumya Sarkar, Sinu Mathew, Sreetosh Goswami, Shafeque, Adam, and T. Venkatesan, Phys. Rev. Lett. 125 (2020) 086803

Sinu Mathew completed Ph.D from Institute of Physics, Bhubaneswar, India in 2008 and moved to national university of Singapore (NUS) as a postdoc research fellow in the department of ECE and from 2011 at NUS Nanoscience & Nanotechnology Institute (NUSNNI). He came back to India in 2016 and joined as Assistant Prof. position at department of Physics, S. B. College, Mahatma Gandhi University, Kottayam, and since then he was a visiting research fellow at NUSNNI until 2019. Sinu’s research interests are the growth of 2D materials, optical properties of transition metal dichalcogenides (TMDC), integration of TMDC with functional oxides and ion beam tailoring of 2D materials and their heterostructures, and layered solids.
He has more than 25 publications in reputed journals such as Adv. Mater, ACS Nano, PRB,PRL, Small etc. He is a key player in the very recent discovery of a new quasi particle called “polaronic trion” and also “monolayer like strong luminance from multilayer MoS₂“in MoS₂/STO system. His works on magnetism in multilayer MoS₂ and in C₆₀ thin films received wide citations. He has been awarded a coordinated research project by International Atomic Energy Agency (IAEA) in 2017 and also nominated for IAEA technical meeting on Ion Beam-Induced Spatio-temporal structural evolution of matter. He is also selected for peer-reviewing of science research projects submitted to national center of science and technology evaluation (NCSTE) Kazakhstan.