Title : Unconventional quasiparticle dynamics in nickel nanoparticles
Abstract:
Nanoscale metallic nanoparticles (NPs) are of special interest for exploring their novel electronic and thermal transport properties at nanoscale. It is because they may have insulating matrix or surfactant/s as well as collective and correlation-driven effects between the NPs producing novel properties relative to bulk counterpart. The transport properties of NPs mainly depend on competition of mean energy level spacing, Coulomb charging energy for a single particle and tunnel energy associated with the inter-particle coupling. We investigated the electrical and thermal transport properties of compacted nickel NPs with crystallite size from 23.1±0.3 to 1.3±0.3 nm. They exhibit an evolution of metal to insulator transition, change in the conduction type from n- to p-type, anomalously large Lorenz number, colossal Seebeck coefficient of 1.87±0.07 mVK−1, and ultralow thermal conductivity of 0.52±0.05 Wm−1K−1 at 300 K as the crystallite size drops. The electrical resistivity analysis reveals a dramatic change in the electronic excitation spectrum indicating the opening of an energy gap, cotunneling and Coulomb blockade of the charge carriers. Seebeck coefficient shows transport energy degradation of charge carriers as transport level moves away from the Fermi level with decrease in crystallite size. The Lorenz number rises to about four orders of magnitude in the metallic regime with decrease in crystallite size, and shows a vivid violation of the Wiedemann–Franz law. Such an observation provides the compelling confirmation for unconventional quasiparticle dynamics where the transport of charge and heat is independent of each other. Therefore, these NPs provide an intriguing platform to tune the charge and heat transport, which may be useful for thermoelectrics and heat dissipation in nanocrystal array-based electronics.
Audience Take Away:
- The audience will be able to learn the novel electrical and thermal properties associated with unconventional quasiparticle dynamics in nickel nanoparticles.
- They can plan for similar experiments with the change in the type of surfactants to prepare the nanoparticles and investigate such properties.
- They may not be necessarily the same as to what we have observed since the surfactants also have unique influences on such properties.
- Similar approach can be followed in the metal nanoparticles to check for similar properties or completely unique properties and so on. Therefore, other faculty members can follow this research to expand their research or teaching, and this will help the audience in their jobs.
- This research does provide a practical solution to a problem that could simplify or make a designer’s job more efficient like implementation of making a new thermoelectrics.
