Milan Sanyal | Saha Institute of Nuclear Physics (original) (raw)

Papers by Milan Sanyal

We report here a comparison of electronic transport properties of conducting polymer nanowires sy... more We report here a comparison of electronic transport properties of conducting polymer nanowires synthesized by chemical and electrochemical methods inside nanopores. Electronic transport properties of these nanowires show a power-law behavior (I µ V 1+b ) at low temperature. Chemically synthesized nanowires exhibit higher values of b and these values increase further with the diameter of nanowires. Zero bias differential conductance of all the nanowires increase with increasing diameter and temperature but the obtained values of chemically synthesized nanowires were always found to be much lower. These results indicate enhancement of electron-electron interactions in chemically synthesized nanowires.

Small, 2006

The development of synthetic processes for oxide nanomaterials is an issue of considerable topica... more The development of synthetic processes for oxide nanomaterials is an issue of considerable topical interest. While a number of chemical methods are available and are extensively used, the collaborations are often energy intensive and employ toxic chemicals. On the other hand, the synthesis of inorganic materials by biological systems is characterized by processes that occur at close to ambient temperatures and pressures, and at neutral pH (examples include magnetotactic bacteria, diatoms, and S-layer bacteria). Here we show that nanoparticulate magnetite may be produced at room temperature extracellularly by challenging the fungi, Fusarium oxysporum and Verticillium sp., with mixtures of ferric and ferrous salts. Extracellular hydrolysis of the anionic iron complexes by cationic proteins secreted by the fungi results in the room-temperature synthesis of crystalline magnetite particles that exhibit a signature of a ferrimagnetic transition with a negligible amount of spontaneous magnetization at low temperature.

Physical Review B, 2007

We have presented here results of a low temperature transport study of polypyrrole nanowires havi... more We have presented here results of a low temperature transport study of polypyrrole nanowires having low electron densities, which shows characteristics of charge density waves observed in structurally ordered materials. The current-voltage characteristics of all these nanowires show a power-law dependence on voltage and temperature and a "gap" that decreases rapidly as the temperature is increased, confirming the existence of a long-range electron-electron interaction in the nanowires. A switching transition to highly conducting state has been observed above a threshold voltage, which can be tuned by changing the diameters of the nanowires and the temperature. Negative differential resistance and enhancement of noise have been observed above the threshold. These experimental results give evidence in favor of Wigner crystallization in these nanowires.

Nanotechnology, 2008

Tunable bistable and multistable resistance switching in conducting polymer nanowires has been re... more Tunable bistable and multistable resistance switching in conducting polymer nanowires has been reported. These wires show reproducible switching transition under several READ-WRITE-ERASE cycles. The switching is observed at low temperature and the ON/OFF resistance ratio for the voltage biased switching transition was found to be more than 10 3 . Current biased measurements show lower ON/OFF ratio and some of the nanowires exhibit a multistable switching transition in current biased measurements. The threshold voltage for switching and the ON/OFF resistance ratio can be tuned by changing doping concentration of the nanowires.

Applied Physics Letters, 2009

Negative capacitance has been observed in conducting polymer nanowires. These nanowires exhibit f... more Negative capacitance has been observed in conducting polymer nanowires. These nanowires exhibit features of one-dimensional Wigner crystals, such as switching transition that reduces resistance by several orders of magnitude, negative differential resistance, and enhancement of noise in the switched state. Negative capacitance is theoretically predicted characteristic feature of a Wigner crystal. The magnitude of negative capacitance increases with increasing bias voltage below the switching transition. Above switching transition the magnitude decreases with increasing current bias. The capacitance goes from negative to positive value as the features of Wigner crystal state disappear with increasing temperature.

Arxiv preprint cond-mat/0702009, 2007

Abstract: The search for theoretically predicted Wigner crystal in one-dimensional (1D) wires of ... more Abstract: The search for theoretically predicted Wigner crystal in one-dimensional (1D) wires of structurally disordered materials exhibiting properties of charge-density-waves have remained unsuccessful. Based on the results of a low temperature conductivity study we ...