[Paper Review] Coexistence of Diamagnetism and Vanishingly Small Electrical Resistance at Ambient Temperature and Pressure in Nanostructures

Dev Kumar Thapa, Saurav Islam+8 more|arXiv (Cornell University)|Jul 23, 2018

Physics of Superconductivity and Magnetism1 references22 citations

TL;DR

This study reports the coexistence of vanishingly small electrical resistance (~2 μΩ) and strong diamagnetism below a critical temperature (T_C up to 286 K) in nanostructured silver particles embedded in a gold matrix, achieved at ambient temperature and pressure. The material exhibits resistivity (~10^{-12} Ω·m) four orders of magnitude lower than noble metals, suggesting potential for room-temperature superconductivity in engineered nanostructures.

ABSTRACT

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.

Motivation & Objective

• To discover ultra-low resistance conductors and superconductors operable at ambient conditions.
• To investigate the coexistence of superconducting-like resistance and diamagnetism in nanostructured materials.
• To engineer a system where T_C can be tuned above room temperature.
• To explore the physical mechanisms enabling resistance vanishing and diamagnetic response in nanostructured composites.

Proposed method

• Fabrication of thin films and pellets using silver nanoparticles embedded in a gold matrix via controlled synthesis and sintering.
• Measurement of electrical resistance and magnetic susceptibility across varying temperatures to identify T_C.
• Use of SQUID-based magnetometry to quantify diamagnetic response and confirm Meissner-like behavior.
• Tuning of T_C through control of silver nanoparticle size, distribution, and matrix composition.
• Analysis of resistivity using four-point probe techniques to isolate intrinsic material behavior from contact resistance.
• Systematic variation of nanostructure morphology to correlate structural parameters with superconducting transition temperature and resistance suppression.

Experimental results

Research questions

• RQ1 Can vanishingly small electrical resistance and strong diamagnetism coexist in a nanostructured material at ambient temperature and pressure?
• RQ2 What is the maximum achievable T_C in Ag/Au nanostructures, and can it be tuned above room temperature?
• RQ3 To what extent does the resistivity of the Ag/Au nanostructure approach the quantum resistance limit?
• RQ4 What is the nature of the magnetic response below T_C, and does it confirm Meissner-like expulsion of magnetic fields?
• RQ5 How do nanostructure morphology and composition influence the superconducting transition and resistance suppression?

Key findings

• Electrical resistance drops below ~2 μΩ below T_C, limited only by measurement uncertainty, indicating near-zero resistance behavior.
• Resistivity reaches ~10^{-12} Ω·m, at least four orders of magnitude lower than that of elemental gold, silver, or copper.
• Volume magnetic susceptibility reaches -0.056 below T_C, confirming strong diamagnetic response.
• T_C reaches as high as 286 K (13°C), demonstrating superconducting-like behavior at near-ambient conditions.
• T_C can be tuned to higher temperatures through controlled nanostructure engineering of silver particle size and distribution.
• The coexistence of near-zero resistance and strong diamagnetism in a single material system supports the emergence of unconventional superconductivity in nanostructured composites.