The Thirring model is a quantum field theory describing self-interactions of the Dirac field in 1+1 dimensions. It evinces a non-trivial zero-temperature phase structure in the mass-interaction plane, with gapless (critical) and gapped (massive) phases separated by a Berezinskii-Kosterlitz-Thousless-type transition. We explore the real-time dynamics to study dynamical phase transitions, using variational uniform MPS and a time-dependent variational principle.  Our exploratory results were presented in several national and international workshops.

Related Presentation

1. Investigating dynamical quantum phase transitions in the massive Thirring model using matrix product states. Lattice 2023 [Link] [Pdf]

2. Thirring model from tensor networks - phase structure and real-time dynamics. 19 Nov, 2020. Perimeter Institute. [Link]

3. Phase Structure and Real-Time Dynamics of 1+1 dimensional massive Thirring model from matrix product states. 9 Dec 2020. NCTS Annual Theory Meeting 2020: Particles, Cosmology, and Strings. [Link] [Video]

Memristive devices have shown attraction for artificial synapses in huge-scale artificial neural networks due to their natural synaptic response, fast writing ability, long retention time, very simple architecture, low energy consumption, and compatibility with 3D CMOS integration. Therefore, In this project, we aim to study the brain-inspired Neuromorphic computing using multifunctional memristive devices for simulating the human brain. 

Publications

1. A. Saleem, D. Kumar, A. Singh*, S. Rajasekaran, T.-Y. Tseng, Oxygen Vacancy Transition in HfOx-Based Flexible, Robust, and Synaptic Bi-Layer Memristor for Neuromorphic and Wearable Applications. Adv. Mater. Technol. 2022, 2101208. 

2. C.-L. Hsu, A. Saleem, A. Singh, D. Kumar, and T.-Y. Tseng, “Enhanced Linearity in CBRAM Synapse by Post Oxide Deposition Annealing for Neuromorphic Computing Applications,” IEEE Trans. Electron Devices, pp. 1–7, 2021.

This project aims to study the sensing properties of different 2D materials. We explore the band structure, adsorption characteristics, charge transfer mechanism, and electronic properties of materials in the presence of toxic gases. We also study the desorption of gases in the presence of a gated external electric field; this helps us to analyze the FET-based sensors' characteristics.

Publications

1. A. Singh, H. Bae, T. Hussain, H. Watanabe, H. Lee, Efficient Sensing Properties of Aluminum Nitride Nanosheets toward Toxic Pollutants under Gated Electric Field, ACS Appl. Electron. Mater. 2020 2 (6), 1645-1652 . 

2. A. Singh, H. Bae, S. Lee, K. Shabbiri, T. Hussain, H. Lee, Highly sensitive and selective sensing properties of modified green phosphorene monolayers towards SF6 decomposition gases, Appl. Surf. Sci. 512 (2020) 145641. 

This project aims to study the behavior of the dielectric properties of 2D materials and their heterostructure. We also analyzed the combined effect of vacancies and dipole interaction, polarization, and dependence on the dielectric constant. 

Publications

1. A. Singh, S. Lee, H. Bae, J. Koo, L. Yang, H. Lee, Theoretical investigation of the vertical dielectric screening dependence on defects for few-layered van der Waals materials, RSC Adv. 9 (2019) 40309–40315. 

2. A. Singh, S. Lee, H. Lee, H. Watanabe, Dielectric Constant and van der Waals Interlayer Interaction of MoS2-Graphene Heterostructures, in: 2020 IEEE 15th Int. Conf. Nano/Micro Eng. Mol. Syst., 2020: pp. 490–494. 

We performed density function theory calculations to study the effect of strain on electronic properties of pristine and doped graphene. A dramatic change in density of states (DOS) and band structure is observed on doped graphene in the presence of uniaxial and biaxial strain. It is found that the presence of dopants at low concentration can enhance the sensitivity of the sensor making it an ultrasensitive high-performance sensor which can sense strain up to ∼0.0001 at low doping concentration, which is almost impossible for currently used sensors, thus transforming graphene into an efficient strain sensing material.

Publications

1. A. Singh, S. Lee, H. Watanabe, H. Lee, Graphene-Based Ultrasensitive Strain Sensors, ACS Appl. Electron. Mater. 2 (2020) 523–528. 

Currently, we are analyzing the the quantum superposition of electron states in a gated vdW heterostructure as a charge qubits. The quantum state is prepared by applying a vertical electric field, is manipulated by short field pulses, and is measured via electric currents.