Discovery and control of high-Z materials - Beyond Mott and topological materials

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

NON-TECHNICAL DESCRIPTION It is widely recognized that whoever controls materials controls technology. Emerging technologies increasingly require new single-crystal materials for definitive studies of fundamental properties, and successful integration of their properties into state-of-art device structures. A large number of quantum materials that are driven by competing fundamental interactions have yet to be explored and understood. It is these quantum materials that the PI seeks to discover, synthesize, and study. U.S. leadership in Science and Technology requires drastically increasing the number of scientists who possess skills in both the synthesis and characterization of new materials. The current situation presents an urgent national challenge that could ultimately undermine the Nation’s economic competitiveness, if left unaddressed. This project addresses this problem by providing rigorous training of graduate and undergraduate students, who are the future human capital for technologies that drive the economy. TECHNICAL DESCRIPTION Novel quantum materials can exhibit surprising or even revolutionary physical properties necessary for critical advances in science and technology. This project focuses on strongly correlated materials with strong spin-orbit interactions that are manifested in strong quantum effects that can be induced by surprisingly weak external stimuli. Recent research dictates the project address the following four topics unique to the high-Z materials: (1) Electric-current control of quantum states. Electric-current control of structural and physical properties is a long-sought but elusive goal of science and technology. The PI’s recent work demonstrates that strong spin-orbit interactions in a distorted Mott insulator is sufficient to realize this important goal. (2) Delicate quantum liquid in un-frustrated trimer lattices and beyond: Ba3n+1Ir3nO9n+1 (n=1,2,). Quantum spin liquids are among the most intensively sought states of matter. Although theoretically predicted, they have not been experimentally observed. PI’s preliminary work revealed an anomalously strong frustration in the trimer lattice Ba4Ir3O10, and a critical role of Ir3O12 trimers in producing spin entanglement. Single crystals of the trimer series Ba3n+1Ir3nO9n+1 the PI has recently synthesized will provide a new paradigm in the search for novel phases of matter. (3) Loop-current-driven colossal magnetoresistance without magnetic polarization: Magnetic polarization usually reduces electron scattering and electrical resistance in almost all materials and is an essential ingredient of colossal magnetoresistance. The PI most recently discovered Mn3Si2Te6 and Ca3Ru2O7 are surprising exceptions to this rule. The electrical resistivity drops by up to 9 orders of magnitude, but only when the magnetic polarization is avoided, implicating a new type of electrical transport yet to be explored. (4) Discovery and synthesis of new quantum materials. A successful effort to discover novel phenomena requires a persistent pursuit of new materials, which has been an essential part of the PI’s research. The crystal synthesis effort will focus on materials with comparable spin-orbit interactions and electron correlations. The phenomena to be studied defy conventional precedents and pose far-reaching scientific and technological breakthroughs. The project brings to bear combined assets of proven expertise, comprehensive experimental facilities, and broad collaborations that complement in-house research. 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.