The field of Condensed Matter Physics and Materials Science integrates the knowledge and tools of chemistry and physics with the principles of engineering to understand and optimize the behavior of materials, as well as to create new and improved materials to help fulfill the missions of the Department of Energy.
Condensed-Matter Physics & Materials Science Seminar
"Complexity in Spin-Frustrated Rock-Salt Manganites"
Presented by Alexandros Lappas, Fulbright Fellow, Institute of Electronic Structure and Laser, Foundation for Research and Technoloogy, Greece
1:30 pm, ISB Bldg. 734 Seminar room 201
Tuesday, November 1, 2016, 1:30 pm
Hosted by: ''Emil Bozin''
Complexity in transition metal oxides is the outcome of simultaneously active electron degrees of freedom (spin-charge-orbital) and their evolution under the restrictions imposed by the underlined crystal lattice. Consequently, the materials' response to competing states requires that we assess structural correlations across a wide range of length and time scales. Taking advantage of cutting-edge structural facilities accessed at neutron [1, 2], synchrotron X-ray  and electron microscopy  labs we address current limitations in understanding the crystallographic structure of layered rock-salt type triangular-lattice manganites of the AMnO2 type (A= Na, Cu). Our capability to recognize how structural rearrangements impact electronic fluctuations reflects on the spin dynamical response of such materials, seen by the complementary time-windows of 23Na-NMR and muon-spin relaxation (μ+SR) local probe methods [3, 5]. The unexpected coexistence of long- and short-range magnetic correlations due to two major opposing effects (elastic vs. magnetic exchange) of similar magnitude, lead to nearly equivalent, competing structural phases enabling infinitesimal quenched disorder to locally lift the differing degree of inherent frustration in the parent AMnO2 phase (with A= Na, TN= 45 K and A= Cu, TN= 65 K) . These manganites provide a paradigm of a rarely observed nanoscale inhomogeneity in an insulating spin system, an intriguing complexity of competition due to geometrical frustration. The dramatic impact of topology and site-disorder on frustrated magnetism is further demonstrated by the hydrated variant of the NaMnO2 antiferromagnet, which gives way to a strongly interacting spin-glass state (Tf= 29 K), indicative of the subtle balance of competing processes in multivalent two-dimensional systems .  M. Giot et al., Phys. Rev. Lett. 2007, 99, 247211.  C. Vecchini et al., Phys. Rev. B 2010, 82, 094404. A. Zorko et al., Nat. Commun. 2014, 5 A.M
Explores the electronic structure and electrodynamics of topological insulators and strongly correlated electron systems, with particular attention to emergent phenomena, such as superconductivity and magnetism, using angle-resolved photoemission (ARPES) and optical spectroscopy.
Studies the role of antiferromagnetism in high-temperature superconductors. The interaction of charge carriers with magnetic moments is of critical importance but remains a challenge to understand. .
Carries out basic studies of the structural, electronic and magnetic properties of condensed matter systems using synchrotron-based x-ray scattering techniques. .
Conducts basic research over a wide swath of theoretical physics, ranging from strongly correlated electrons to first principle electronic structure theory.
Studies both the microscopic and macroscopic properties of complex and nano-structured materials with a view to understanding and developing their application in different energy related technologies
Addresses key open questions in HTS physics such as the dimensionality of the HTS phenomenon, the spin and charge of free carriers, the nature of the superconducting transition, the role of charge stripes (if any) in the HTS state, the nature of the overdoped metallic state, and more.
Span a wide range of quantum matter systems, including superconductors, superfluids, supersolids, electronic liquid crystals, topological insulators superconductors & superfluids, heavy fermions, and spin liquids. Throughout, the focus is on development of innovative techniques and approaches to each problem.
Utilizes advanced electron microscopy techniques to study nanoscale structure and defects that determine the utility of functional materials, such as superconductors, multiferroics, and other energy related systems including thermoelectrics, photovoltaics, and batteries.
The Condensed Matter Physics and Materials Science Department is part of Brookhaven National Laboratory's Energy Sciences Directorate.