Raman Spectroscopy Group and Users Center
The Raman spectroscopy group is focused on studies of charge and spin ordered ground states in strongly correlated electron systems. Our current aim is to investigate them with Raman spectroscopy to find general behavior for materials of different chemical origin (both organic and inorganic).
Click here if you are interested in the Johns Hopkins Raman Users Center.
Publications of our group can be found at Google Scholar
Shreenanda Ghoch has started her posdoc position. Welcome, Shreenanda!
Our paper with Predrag Nikolic on elecectronic scattering of Nd2Ir2O7 and Pr2Ir2o7 demonstrating how Raman scattering can prove Weyl and Luttinger semimetals is now on arxiv: Weyl-Luttinger phase transition in pyrochlore iridates revealed by Raman scattering
Yu Fei Liu, an undergraduate majoring in physics, is joining our group for an undergraduate research project.
Welcome, Yu Fei!
Jackson Davis joined our group to study molecular quantum materials using Raman spectroscopy.
Paper by Y. Xu et al "Importance of dynamic lattice effects for crystal field excitations in quantum spin ice candidate Pr2Zr2O7" is published in Phys.Rev. B.
Paper by Y. Xu et al "Phonon spectrum of Pr2Zr2O7 and Pr2Ir2O7 as an evidence of coupling of the lattice with electronic and magnetic degrees of freedom" is now on arxiv
"Ferromagnetism out of charge fluctuation of strongly correlated electrons in κ-(BEDT-TTF)2Hg(SCN)2Br"
Our paper by Y. Xu et al "Importance of dynamic lattice effects for crystal field excitations in quantum spin ice candidate Pr2Zr2O7" is now on arxiv.
We use Raman spectroscopy to uncover dynamic interactions of the lattice of Pr2Zr2O7 with crystal field excitations of Pr atom.
We show how we can probe the ground state splitting by measuring a transition to the first excited state
Arman Jasuja, an undergraduate majoring in physics is joining group to work on Raman spectroscopy of molecular quantum materials.
Our paper "Impact of the lattice on magnetic properties and possible spin nematicity in the S=1 triangular antiferromagnet NiGa2S4" is published in Phys. Rev. Letters.
Many theoretical papers discuss a possibility for nematic order driven by quadrupole interactions in NiGa2S4. Using Raman spectroscopy, we identify a phonon which can produce quadrupole interactions by modulation of the nearest neighbor magnetic exchange.
Jesse Liebman joined our group to work on understanding of a connection between organic-based dipole liquid and spin liquid.
Our joint paper with collaborators from the University of Tokyo and NIMS, Tsukuba "Ferromagnetism out of charge fluctuation of strongly correlated electrons in κ-(BEDT-TTF)2Hg(SCN)2Br" is now on arxiv.
Here we present experimental studies of magnetic properties of the quantum dipole liquid κ-(BEDT-TTF)2Hg(SCN)2Br. We observe a rise of ferromagnetic correlations as dipole fluctuations develop. We suggest how charge fluctuations in an intrinsically inhomogeneous system close to a phase transition can lead too ferromagnetic interactions.
Our paper "Melting of charge order in the low-temperature state of an electronic ferroelectric" is published in npj Quantum Materials
In this work we demonstrate a unique re-entrant transition in a Mott insulator on a weakly anisotropic triangular lattice κ-(BEDT-TTF)2Hg(SCN)2Cl. Using Raman spectroscopy, we observe how a charge ordered ferroelectric looses the order on cooling to low temperatures.
Tom and his group learned how to control dimensionality of MoS2 structures by a substrate on which a film is growing. Photoluminescence and Raman scattering measured in our lab were one of the principle ways to characterize 1D MoS2 filaments and their electronic structure.
Chris Hennighausen is an undergraduate student in Boston University majoring in physics. Chris joined our group for summer and is helping us to set up our new lab
Mae Rowland, a student from Maryland Institute College of Art (MICA) and an artist in residence in HEMI has joined our group for summer. Mae wants to learn about light and how incorporate various light effects into her art .
Gwen Tsai, an undergraduate majoring in Chemical Engineering joined our group for a summer research project. Gwen will use micro-Raman scattering to look for microplastic particles in environmental samples. This project is run in collaboration with JHU School of Public Health.
We moved to a new large lab space!!! Now we are located in room 140, Bloomberg
Our new paper on SmB6, a collaboration with quantum chemists (group of Prof. A. Alexandrova, UCLA) is submitted to the arxiv: https://arxiv.org/abs/1903.10650.
Our work shows that B6 cage is not as rigid and irrelevant to the properties of SmB6 as was thought before. Starting with a small cluster, calculations show how borons from neighboring unit cells can be considered as a B2 cluster. A variation of the length of bond in this pair creates two potential minima, for Sm2+ and Sm3+. Our Raman scattering data support the findings on a coupling of boron motion to the electronic bands of Sm. This approach could be a key to explain the mixed valence state of SmB6, its heat capacity, and many other properties.
Our paper on quantum dipole liquid state is published in Science magazine.
N. Hassan, S. Cunningham, M. Mourigal, E. I. Zhilyaeva, S. A. Torunova, R. N. Lyubovskaya, J. Schlueter, N. Drichko. "Evidence for a quantum dipole liquid state in an organic quasi-two-dimensional material", Science 360, 1101 (2018).