arXiv subjects

Phanibhusan Singha Mahapatra

Publications and source records attributed to Phanibhusan Singha Mahapatra.

3 recordsLinked to original sources

arXiv2025

Fabrication of A Dual Gated Mirror Symmetric Twisted Trilayer Graphene Device to Study Superconductivity

Though research on graphene by itself has waned, the interest in moire materials, materials made with stacked layers of graphene with a rotational twist between the layers, has exploded in popularity. These layered devices show a key feature, flat bands. Flat bands localize electrons, which in turn leads to the expression of correlated states such as Mott insulators, superconductivity, and more. A key property of these devices is that their 2D nature allows us to tune them in situ, effectively allowing us to change the device's electronic properties. This powerful ability greatly reduces the time and money required to study superconductivity. The superconductivity in these systems seems to be similar to high-temperature superconductors such as cuprates, giving us a path towards studying high-temperature superconductivity. The fabrication of these devices is nontrivial, and thus we detail one general way to create these layered devices to give maximal tunability.

cond-mat.mes-hall↗

arXiv2019

Current-voltage characteristics in Ag/Au nanostructures at resistive transitions

Transitions to immeasurably small electrical resistance in thin films of Ag/Au nanostructure-based films have generated significant interest because such transitions can occur even at ambient temperature and pressure. While the zero-bias resistance and magnetic transition in these films have been reported recently, the non-equilibrium current-voltage ($I-V$) transport characteristics at the transition remains unexplored. Here we report the $I-V$ characteristics at zero magnetic field of a prototypical Ag/Au nanocluster film close to its resistivity transition at the critical temperature $T_{C}$ of $\approx160$ K. The $I-V$ characteristics become strongly hysteretic close to the transition and exhibit a temperature-dependent critical current scale beyond which the resistance increases rapidly. Intriguingly, the non-equilibrium transport regime consists of a series of nearly equispaced resistance steps when the drive current exceeds the critical current. We have discussed the similarity of these observations with resistive transitions in ultra-thin superconducting wires via phase slip centres.

cond-mat.mes-hall↗

arXiv2019

Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures

The great practical utility has motivated extensive efforts to discover ultra-low resistance electrical conductors and superconductors in ambience. Here we report the observation of vanishingly small electrical resistance at the ambient temperature and pressure conditions in films and pellets of a nanostructured material that is composed of silver particles embedded into a gold matrix. Upon cooling below a sample-specific temperature scale ($T_{C}$) as high as $286$ K, the film resistance drops below $\sim 2μΩ$, being limited by measurement uncertainty. The corresponding resistivity ($\sim 10^{-12}$ $Ω$.m) is at least four orders of magnitude below that of elemental noble metals, such as gold, silver or copper. Furthermore, the samples become strongly diamagnetic below $T_{C}$, with volume susceptibilities as low as -0.056. We additionally describe methods to tune $T_{C}$ to temperatures much higher than room temperature.

cond-mat.supr-con↗