Ph. D. Thesis Colloquium
Name: Mr. Uddipan Ghosh
Research Supervisor: Prof. Anshu Pandey
Title: Emergent Opto-electronic Phenomena in Responsive Nanocrystal Solids
Date and Time: Thursday, 05th November 2026 at 11:00 a.m.
Venue: Rajarshi Bhattacharyya Memorial Lecture Hall, Chemical Sciences Building
Abstract:
Electrical transport in nanocrystal solids continues to generate considerable interest due to emergent macroscopic behaviour that is not a predictable outcome of the microscopic properties of individual grains. Transport in nanocrystal solids is governed by weak junctions between grains. Transport from one grain to another is an immensely complex interplay of both quantum effects (tunnelling) and thermodynamic ones (thermal activation, equilibration and relaxation). In this process, charging energy, disorder and grain geometry all compete to determine an outcome. In such weakly coupled granular systems, charge carriers thus flow through a tortuous network of percolating paths.1 In this thesis, I study the nonlinear response of a silver-based granular memristive system and show how it gives rise to a wide variety of emergent opto-electronic properties, with applications in nonlinear optics, data encryption and neuromorphic computing.
First, I discuss the noise characteristics of the memristive system under a constant electric field and explain its power-law behaviour within the framework of the Marcus-Tang electron-transfer model of quantum-dot blinking. I then present methods to tune this noise, opening a pathway towards its use in non-von Neumann computing.2
Next, I show how the noise in this system can be harnessed to produce a non-classical state of light. I discuss the practical use of such a correlated source for probing optical nonlinearities and its advantages over conventional high-power coherent sources.3
I also demonstrate how the intrinsic randomness of this system can be harvested to generate true random numbers for encryption-key generation.4
In the final part of the thesis, I will show how the highly complex percolating paths in granular media closely resemble the neuronal interconnections in the brain. I use this as a motivation to explore how brain-like behaviour can be mimicked using the granular system.5 I discuss my work demonstrating its potential for neuromorphic computing, including how its memory can be tuned to suit different computational problems.
References:
1. Bhaumik, A. & Pandey, A. Theoretical analysis of electron transport in perovskite thin films. Physical Chemistry Chemical Physics 26, 25670–25677 (2024).
2. Ghosh, U., Bhaumik, A., Vasudeva, N. & Pandey, A. Granular memristors with tunable stochasticity. Nanoscale 17, 1238–1245 (2025).
3. Ghosh, U., Roy, P., Kumar, V. & Pandey, A. Engineered Superbunched Source of Light Based of Stochastic Granular Memristor as A Probe for Nonlinear Optics (Under Review).
4. Ghosh, U., Saha, M., Bhaduri, A. & Pandey, A. Granular Memristor-Driven Photonic True Random Number Generation. ACS Applied Optical Materials https://doi.org/10.1021/acsaom.6c00481 (2026) doi:10.1021/acsaom.6c00481.
5. Bhaumik, A. et al. Emergent neuro-mimetic oscillations in engineered granular assemblies. Mater. Horiz. https://doi.org/10.1039/D6MH00086J (2026) doi:10.1039/D6MH00086J.