arXiv subjects

Tathagata Paul

Publications and source records attributed to Tathagata Paul.

5 recordsLinked to original sources

arXiv2025

Engineering Magnetotransport Through Hierarchical Symmetry in Weyl Semimetal Superlattices

Superlattice engineering is a powerful way to tune the transport properties of a material. In this work we show that magnetotransport can be modified by superlattices in 3D materials based on the relative symmetry between the Fermi-surface and superlattice. We demonstrate commensuration oscillations in the ballistic transport regime of a nanostructured 3D material with the Weyl semimetal NbP, a signature typically limited to superlattices in 2D materials. The behavior of the oscillations encodes information about the shared properties between the quasiparticles at the Fermi-surface--including their momentum, charge, mass, and rotational symmetry--and the structure of the superlattice. The magnetic field and temperature dependence of the commensuration oscillations enables us to extract the Fermi-momenta and quasiparticle mass at an order of magnitude lower magnetic field and higher temperature than Shubnikov-de Haas quantum oscillations. Furthermore, we use a chiral superlattice to engineer asymmetric longitudinal magnetoresistance based on the charge of the quasiparticles and superlattice enantiomer. These results demonstrate nanopatterned superlattices as an effective method for fermiology, and also point towards new ways of engineering quantum transport in these systems based on the mutual properties of the superlattice and Fermi-surface.

cond-mat.mes-hall↗

arXiv2022

Electronic Poiseuille Flow in Hexagonal Boron Nitride Encapsulated Graphene FETs

Electron-electron interactions in graphene are sufficiently strong to induce a correlated and momentum-conserving flow such that charge carriers behave similarly to the Hagen-Poiseuille flow of a classical fluid. In the current work, we investigate the electronic signatures of such a viscous charge flow in high-mobility graphene FETs. In two complementary measurement schemes, we monitor differential resistance of graphene for different channel widths and for different effective electron temperatures. By combining both approaches, the presence of viscous effects is verified in a temperature range starting from 178 K and extending up to room temperature. Our experimental findings are supported by finite element calculations of the graphene channel, which also provide design guidelines for device geometries that exhibit increased viscous effects. The presence of viscous effects near room temperature opens up avenues for functional hydrodynamic devices such as geometric rectifiers like a Tesla valve and charge amplifiers based on electronic Venturi effect.

cond-mat.mes-hall↗

arXiv2020

Gate-controllable electronic trap detection in dielectrics

Gate controllable electronic trap detection method has been demonstrated by regulating the gate potential of MIS devices. This method is based on shift of capacitance voltage (CV) curve as well as flatband voltage (VFB) measure in less than 10 micro-seconds due to injection or ejection of electrons through the metal gate. Using this method, an electronic trap energy distribution was measured in the HfO2 dielectric film and it confirms a maximum number of traps (Delta_NT) of 1.7x1012 cm-2 corresponding to an energy level (Delta_EIL) of 0.45 eV above silicon conduction band (Si-ECB). In comparison, ZrO2-based MIS devices showed a broader distribution of electronic traps throughout the band gap. However, HfO2 contained more than 60% traps in deep level compared to 50% in ZrO2, which establishes the effects of material variation.

physics.app-ph↗

arXiv2019

A high-performance MoS2 synaptic device with floating gate engineering for Neuromorphic Computing

As one of the most important members of the two dimensional chalcogenide family, molybdenum disulphide (MoS2) has played a fundamental role in the advancement of low dimensional electronic, optoelectronic and piezoelectric designs. Here, we demonstrate a new approach to solid state synaptic transistors using two dimensional MoS2 floating gate memories. By using an extended floating gate architecture which allows the device to be operated at near-ideal subthreshold swing of 77 mV/decade over four decades of drain current, we have realised a charge tunneling based synaptic memory with performance comparable to the state of the art in neuromorphic designs. The device successfully demonstrates various features of a biological synapse, including pulsed potentiation and relaxation of channel conductance, as well as spike time dependent plasticity (STDP). Our device returns excellent energy efficiency figures and provides a robust platform based on ultrathin two dimensional nanosheets for future neuromorphic applications.

physics.app-ph↗

arXiv2015

Percolative switching in transition metal dichalcogenide field-effect transistors at room temperature

We have addressed the microscopic transport mechanism at the switching or on-off transition in transition metal dichalcogenide (TMDC) field-effect transistors (FET), which has been a controversial topic in TMDC electronics, especially at room temperature. With simultaneous measurement of channel conductivity and its slow time-dependent fluctuation (or noise) in ultra-thin WSe2 and MoS2 FETs on insulating SiO2 substrates, where noise arises from McWhorter-type carrier number fluctuations, we establish that the switching in conventional backgated TMDC FETs is a classical percolation transition in a medium of inhomogeneous carrier density distribution. From the experimentally observed exponents in the scaling of noise magnitude with conductivity, we observe unambiguous signatures of percolation in random resistor network, particularly in WSe2 FETs close to switching, which crosses over to continuum percolation at a higher doping level. We demonstrate a powerful experimental probe to the microscopic nature of near-threshold electrical transport in TMDC FETs, irrespective of the material detail, device geometry or carrier mobility, which can be extended to other classes of 2D material-based devices as well.

cond-mat.mes-hall↗