Strongly Correlated Materials Lab
Research interests: Materials Physics; Condensed matter physics; Quantum magnetism; Geometrically frustrated magnets; Colossal magnetoresistive materials; Strongly correlated electron materials; Complex oxide materials; Neutron spectroscopy; Magnetic measurements; Phonon measurements; Multiferroic materials; Neutron diffraction; X-ray diffraction; Magnetic order; Spin glasses; Spin wave measurements; Short-range spin correlations.
Synopsis: "More is different." - P.W. Anderson
The electron is perhaps one of the simplest objects imaginable: a point particle with mass, charge, and intrinsic angular momentum. And yet, the electrons responsible for the properties of most solid materials can exhibit collective behaviors with properties very different from those of their constituent building blocks. In strongly correlated materials, interactions between electrons yield states that cannot be explained - even qualitatively - by the simple free electron theories that worked so well in understanding the properties of simple metals. These materials then serve as ideal systems in which to explore many-body quantum mechanics, and also attract attention as unique bulk properties such as high-temperature superconductivity offer possible technological applications.
My research interests are focused on understanding the unique quantum mechanical ground states and excitations present in many strongly correlated materials as well as synthesizing new materials. We measure the bulk magnetic, structural, and thermodynamic properties of materials here at USNA, as well as performing neutron spectroscopy studies at national user facilities (such as the NIST Center for Neutron Research) to probe atomic scale collective dynamics.
SELECTED JOURNAL PUBLICATIONS
"Spin wave damping arising from phase coexistence below Tc in colossal magnetoresistive La0.7Ca0.3MnO3" by Joel S. Helton, Susumu K. Jones, Daniel Parshal, Matthew B. Ston, Dmitry A. Shulyatev, and Jeffrey W. Lynn, Physical Review B 96, 104417 (2017).
"Polaron-mediated spin correlations in metallic and insulating La1-xAxMnO3(A=Ca,Sr, or Ba)" by Joel S. Helton, Daniel M. Pajerowski, Yiming Qiu, Yang Zhao, Dmitry A. Shulyatev, Yakov M. Mukovskii, Georgii L. Bychkov, Sergei N. Barilo, and Jeffrey W. Lynn, Physical Review B 90, 214411 (2014).
"Fractionalized excitations in the spin-liquid state of a kagome-lattice antiferromagnet” by Tian-Heng Han, Joel S. Helton, Shaoyan Chu, Daniel G. Nocera, Jose A. Rodriguez-Rivera, Collin Broholm, and Young S. Lee, Nature 492, 406 (2012).
“Paramagnetic spin correlations in colossal magnetoresistive La0.7Ca0.3MnO3” by Joel S. Helton, Matthew B. Stone, Dmitry A. Shulyatev, Yakov M. Mukovskii, and Jeffrey W. Lynn, Physical Review B 85, 144401 (2012).
“Evolution of the commensurate and incommensurate magnetic phases of the S = 3/2 kagome staircase Co3V2O8 in an applied field” by Joel S. Helton, Ying Chen, Georgii L. Bychkov, Sergei N. Barilo, Nyrissa Rogado, Robert J. Cava, and Jeffrey W. Lynn, Journal of Physics: Condensed Matter 24, 016003 (2012).
“Magnetic order of the hexagonal rare earth manganite Dy0.5Y0.5MnO3” by Joel S. Helton, Deepak K. Singh, Harikrishnan S. Nair, and Suja Elizabeth, Physical Review B 84, 064434 (2011).
“Dynamic Scaling in the Susceptibility of the Spin-1/2 Kagome Lattice Antiferromagnet Herbertsmithite” by J.S. Helton, K. Matan, M.P. Shores, E.A. Nytko, B.M. Bartlett, Y. Qiu, D.G. Nocera, and Y.S. Lee, Physical Review Letters 104, 147201 (2010).
“Spin Dynamics of the S=1/2 Kagome Lattice Antiferromagnet ZnCu3(OH)6Cl2” by J.S. Helton, K. Matan, M.P. Shores, E.A. Nytko, B.M. Bartlett, Y. Yoshida, Y. Takano, A. Suslov, Y. Qiu, J.-H. Chung, D.G. Nocera, and Y.S. Lee, Physical Review Letters 98, 107204 (2007).