The electronic devices we use today operate by controlling the motion of negatively charged electrons, known as an electric current, through a material by applying a voltage. However, electrons possess not only an electric charge but also a property known as their intrinsic spin, which is analogous to a spinning top. This has led to the development of electronic devices that function by exploiting both the charge and the spin of electrons in a new form of electricity known as spintronics. Although still in its infancy, this field of spintronics has far reaching potential in applications such as ultra-low power electronics and quantum computing. Recently, a new class of materials, known as fermion materials, topological insulators and semimetals, or just quantum materials, were discovered which allow electronic currents to be controlled using both charge and spin. As part of this Excellence in Research project, supported by the National Science Foundation, a new, strategic partnership between the Department of Physics at Norfolk State University (NSU) and the 2D Crystal Consortium-Materials Innovation Platform (2DCC-MIP) at Pennsylvania State University has been formed. The collaboration between the two groups leverages their respective unique capabilities in single crystal growth, materials characterization, and modeling into a team focused on the discovery of new Weyl semimetals, which are specific solid state crystals that are good candidates for quantum materials. Additionally, this project also strengthens education and training in the field of growth of crystalline materials, the importance of which was highlighted in the National Research Council's report "Frontiers in Crystalline Matter." By providing students with in-depth research training in the NSU Department of Physics and in 2DCC-MIP at Penn State this research has a significant impact on the education, research training, and professional development of at least nine undergraduate physics majors and a graduate student in material science, that are all underrepresented in STEM fields.
Topological fermions such as Dirac and Weyl fermions in condensed matter are not only of fundamental importance, but also carry great promise for information technology applications. Although 3-, 6- and 8-fold fermions have been predicted in a wide range of materials, these predictions are still awaiting experimental verification. The unavailability of single crystal samples of those proposed candidate materials has slowed the progress in this area. This research partnership addresses this challenge by developing a comprehensive strategy to grow and characterize single crystals of the proposed candidate materials. This approach accelerates discoveries of novel topological materials. The new fermion candidate materials which are of interest include: 1) 3-fold fermions Pd3Bi2S2, Ag3SeAu, A4Pn3 (A=Ca, Sr and Ba; Pn=As, Sb and Bi), R4Pn3 (R=La, Ce; Pn =As, Sb and Bi), and ReRh6Ge4 (Re = Y, La and Lu), 2) 6-fold fermions MgPt, PdAsS, K3BiTe3, Mg3Ru2, FeS2 and PtP2, and 3) 8-fold fermions CuBi2O4, PdBi2O4, PdS, CsSn, CsSi, Ta3Sb, MPd3S4(M=rare earth) and Nb3Bi. Materials characterization the research team uses include magnetotransport, quantum oscillation, and ARPES measurements (performed at 2DCCMIP) and XRD, time resolved reflectivity, and transient grating measurements performed at NSU.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
