Quantum phase transitions are changes in the solid state of a material that result from quantum fluctuations instead of temperature changes. These fluctuations are influenced by factors such as pressure, magnetic field, or, in our case, the composition of the material. In superconductors, such as the ZrNi2Ga, alloy, a sharp phase transition occurs at a critical temperature TC and a critical magnetic field HC, below which the material allows current to flow virtually unimpeded. Previous studies have shown that TC for this superconductor is stoichiometry-dependent, which means that adjusting the constituent elements can allow us to adjust TC as well . If TC is pushed down to 0 K, then any phase transition observed must be a quantum phase transition. Finding the compositions at which quantum phase transitions may be observed is important because it provides valuable insight to fundamental quantum behaviors which are at the forefront of many modern research topics. To explore this further, we synthesized a series of 5g ZrNi2-xCuxGa (0.25 < x ≤ 0.5) samples through arc melting followed by annealing and quenching. We investigated the structural composition of the samples through analyzing X-ray diffraction and scanning electron microscopy (SEM) data, then measured the resistivity of the samples at different temperatures and in different magnetic fields to find critical temperatures and critical magnetic fields. We found that samples exhibited the L21 cubic structure at room temperature and demonstrated superconductivity below 2 K, and through extrapolation hypothesized that TC would reach 0 K for x = 0.9 (signifying a corresponding QPT at that value). Moving forward, we will explore the x = 0.9 sample to see if superconductivity is truly destroyed and how this affects the structure and properties of the sample. For further research in materials science, graduate or industrial, this research is crucial for developing an intuitive understanding of the scientific principles behind quantum behavior and phase transitions in general.
Author: Kyra Stillwell
Advisor: Mahmud Khan, Physics
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