David M Fobes
Information Systems & Modeling
Los Alamos National Laboratory
Intro
I received my PhD in Physics from Tulane University where, as a Louisiana Board of Regents Graduate Fellow, I studied the effects of chemical substitution on strongly correlated electron materials using advanced materials synthesis techniques.
Shortly thereafter I joined the Neutron Scattering Group in CMPMSD at Brookhaven National Laboratory, where I investigated the lattice dynamics in iron-based superconductors using neutron spectroscopy, and assisted in the development of a new scattering instrument at Oak Ridge National Lab, HYSPEC. As a former member of MPA-CMMS at Los Alamos National Lab, I am used neutrons to study how magnetic frustration and anisotropy affect emergent phases observed near superconductivity, and the spin dynamics of skyrmion lattices.
My work has generated considerable impact in my field; my more than thirty publications, appearing in journals such as Nature Physics, Nature Materials, and Nature Communications, have already been cited nearly six hundred times. My broader research interests include the complex role of magnetic interactions in quantum materials, which have the potential for future functionality, and machine learning for materials research.
I currently work in the Information Systems and Modeling (A-1) Group at Los Alamos National Laboratory (LANL), working on Power Grid and optimization problems.
Expertise
Neutron Scattering
Using a number of different Time of Flight and Thermal/Cold Triple Axis instruments at Oak Ridge National Laboratory's Spallation Neutron Source (SNS) and High-Flux Isotope Reactor (HFIR), NIST's Center for Neutron Research reactor (NCNR), Helmholtz-Zentrum Berlin (BER-II), Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM-II) and the STFC Rutherford Appleton Laboratory
Single Crystal Synthesis
Materials sythesis of strongly correlated electron materials, such as complex layered oxides, iron chalcogenides, non-centrosymmetric intermetallics, and heavy fermion compounds. Using optical floating zone method with an imaging furnace, flux method, vapor transport method, Bridgman method, Czochralski method, and thermal evaporation of thin films
Polarized Neutron Scattering
Experience with polarized neutron scattering incl. spherical polarimetry with CRYOPAD and a variety of polarizers/analyzers incl. Heusler, supermirror and 3He cells
Sample characterization
Using a variety of methods including resistivity, heat capacity, magnetization and ac susceptibility, neutron and x-ray diffraction (XRD)
X-ray diffraction
Using laboratory X-ray diffractometers, including powder and single crystal x-ray diffraction for sample characterization and structure analysis and Laue X-ray diffraction for determination of sample orientation
Cryogenic Sample Environments
Experience with using a variety of sample environments incl. superconducting magnets, 3He cryostats, and closed-cycle refrigerators, and custom sample holder design.
Software Development
Modeling and data analysis and production of publication/presentation quality figures, development of a custom python library for neutron scattering data analysis (NeutronPy), and instrument control and custom automated measurement program design
Surface Science
Using such techniques as scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDXS), scanning tunneling microscopy (STM), low energy electron diffraction (LEED), X-ray photoemission spectroscopy (XPS) and angle resolved photoemission spectroscopy (ARPES).
Skills
90
%
Python
90
%
numpy
85
%
scipy
95
%
matplotlib
80
%
Julia
85
%
Matlab
75
%
Mathematica
75
%
IDL
70
%
LabView
60
%
C
55
%
C++
95
%
git
95
%
MacOS
75
%
Windows
90
%
*nix
90
%
LaTeX
70
%
OriginPro
10
%
Rust
40
%
Ruby
40
%
Javascript
Experience
2018 – present
Los Alamos National Laboratory
R&D Scientist
Los Alamos, NM
Scientist in the Information Systems and Modeling Group (A-1)
2015 – 2018
Los Alamos National Laboratory
Postdoc Research Associate
Los Alamos, NM
Investigation of the magnetism dynamics of heavy fermion compounds and skyrmion materials using neutron spectroscopy, discovering an intimate connection between the modulated magnetic states of CeRhIn5 and its high nematic susceptibility, and making the first measurements of the spin excitation spectra of skyrmion compound MnSi via neutron Time of Flight spectroscopy. Also designed and successfully tested a versatile new uniaxial strain device for use in small angle neutron scattering
2012 – 2015
Brookhaven National Laboratory
Research Associate
Upton, NY
Study of the lattice dynamics in the iron chalcogenide superconducting family Fe(1+y)Te(1-x)Se(x) using neutron scattering, finding evidence for an orbital ordering transition in parent compound FeTe, appearing as a Bond-Order-Wave, and for an intimate coupling between magnetic fluctuations and the lattice degree of freedom resulting in the appearance of a "forbidden" phonon. Also participated in the comissioning of a hybrid spectrometer (HYSPEC) at Oak Ridge National Lab's Spallation Neutron Source, and began developement of NeutronPy
2010 – 2012
Tulane University
Postdoctoral Research Fellow
New Orleans, LA
Investigation of the superconductivity as a function of excess-Fe content in iron chalcogenide superconductor family Fe(1+y)Te(1-x)Se(x) via materials synthesis, bulk characterization techniques, and neutron scattering
2006 – 2010
Tulane University
Graduate Research Assistant
New Orleans, LA
Study of the orbital physics of layered strontium ruthenates, uncovering the orbital-selective nature of the metamagnetism in Sr4Ru3O10, unusual switching behavior in Ca3Ru2O7, and showing the viability for bolometric detection of Ca2RuO4
2004 – 2006
Tulane University
Undergraduate Research Assistant
New Orleans, LA
Floating zone single crystal synthesis of layered perovskite ruthenates of the Ruddlesden-Popper series, focusing on studying the effects of dopants such as Ca for Sr, and Ti for Ru
Education
2006 – 2010
Tulane University
Doctor of Philosophy (Ph.D.) in Physics
New Orleans, LA
Dissertation: 'Orbital dependence of magnetism in layered ruthenate systems'
Advisor: Zhiqiang Mao
2002 – 2006
Tulane University
Bachelor of Science (B.Sc.) in Physics, Math
New Orleans, LA
Professional and Public Service
Awards
Institute for Complex Adaptive Matter (ICAM) Junior Scientist Travel Award (2010)
Awarded to 30 applicants per year, only 5-10 for domestic travel.
Provost's Office Graduate Student Travel Fund, Tulane University (2009)
Travel award to present my research at the 2009 APS March Meeting.
58th Meeting of Nobel Laureates at Lindau: Physics, Attendee (2008)
560 young scientists selected (only 50 from the US) out of 20,000 applicants
Louisiana Board of Regents Graduate Fellowship Grant (2006-2010)
Graduate Studeis support. One award out of approx. 15 incoming graduate applicants in Physics.
National Society of Collegiate Scholars (2003)
Offered to students in their first two years with a 3.4 GPA or greater, and are within the top 20% of their class.
Funding
Neutron Beam Time
Authored and co-authored 66 successful proposals for neutron beam time at various international and domestic neutron sources since 2012, with an acceptance rate of more than 95%. The corresponding allocated beam time consists of of 336 days, which corresponds to approximately $6,720,000 in third party funding, where neutron beam time is typical estimated to cost in excess of ~20,000/day.
ISTI Rapid Response G&A 2018 Cloud Computing
Framework for On-Demand Cloud Computation of Theoretical Models of Materials over Discretized Phase Volumes
Teaching
Students Supervised:
Graduate: 4
Undergraduate: 2
Graduate: 4
Undergraduate: 2
Jan 2017 – Apr 2017
Introduction to Python for Data Analysis and Visualization
Instructor
Los Alamos National Laboratory
Designed and taught a course on introductory Python to members of MPA-CMMS at LANL.
Aug 2008 – Dec 2008
Modern Physics
Private Tutor
Tulane University
Provided private tutoring services for undergraduates in the introductory Modern Physics course
Aug 2008 – Dec 2008
Introduction to Thermodynamics
Private Tutor
Tulane University
Provided private tutoring services for undergraduates in the introductory Thermodynamics course
Aug 2008 – Dec 2008
Partial Differential Equations
Private Tutor
Tulane University
Provided private tutoring services for undergraduates in the Partial Differential Equations course
Jan 2008 – May 2008
General Physics
Private Tutor
Tulane Unversity
Provided tutoring services for students of the undergraduate General Physics course
Sept 2005 – Dec 2005
General Physics
Private Tutor
Rutgers Unversity
Provided tutoring services for students of the undergraduate General Physics course
Publications
h-index: 13
Publications: 36
Citations: 667
(Web of Science)
Publications: 36
Citations: 667
(Web of Science)
Tunable Emergent Heterostructures in a Prototypical Correlated Metal
D. M. Fobes, S. Zhang, S.-Z. Lin, P. Das, N. J. Ghimire, E. D. Bauer, J. D. Thompson, L. W. Harriger, G. Ehlers, A. Podlesnyak, R. I. Bewley, A. Sazonov, V. Hutanu, F. Ronning, C. D. Batista, and M. Janoschek
Anisotropic magnetocrystalline coupling of the skyrmion lattice in MnSi
Y. Luo, S.-Z. Lin, D. M. Fobes, Z. Liu, E. D. Bauer, J. B. Betts, A. Migliori, J. D. Thompson, M. Janoschek, and B. Maiorov
Elasticity in the skyrmion phase unveils depinning at ultra-low current densities
Y. Luo, S.-Z. Lin, M. Leroux, N. Wakeham, D. M. Fobes, E. D. Bauer, J. B. Betts, J. D. Thompson, A. Migliori, M. Janoschek, B. Maiorov
Realization of the Axial Next-Nearest-Neighbor Ising model in U3Al2Ge3
D. M. Fobes, S.-Z. Lin, N. J. Ghimire, E. D. Bauer, J. D. Thompson, M. Bleuel, L. M. DeBeer-Schmitt, and M. Janoschek
Solving quantum riddles with neutron scattering
D. M. Fobes, M. Janoschek
Versatile Strain-Tuning of Modulated Long-Period Magnetic Structures
D. M. Fobes, Y. Luo, N. Leon, E. D. Bauer, V. R. Fanelli, M. A. Taylor, L. M. DeBeer-Schmitt, and M. Janoschek
Ordered hydroxyls on Ca3Ru2O7(001)
D. Halwidl, W. Mayr-Schmölzer, D. Fobes, J. Peng, Z. Q\. Mao, M. Schmid, F. Mittendorfer, J. Redinger, and U. Diebold
Low temperature magnetic structure of CeRhIn5 by neutron diffraction on absorption-optimized samples
D. M. Fobes, E. D. Bauer, J. D. Thompson, A. Sazonov, V. Hutanu, F. Ronning, and M. Janoschek
Forbidden phonon: Dynamical signature of bond symmetry breaking in the iron chalcogenides
D. Fobes, I. A. Zaliznyak, J. M. Tranquada, Z. Xu, G. Gu, X.-G. He, W. Ku, Y. Zhao, M. Matsuda, V. Garlea, and B. Winn
Adsorption of Water at the SrO Surface of Ruthenates
D. Halwidl, B. Stöger, W. Mayr-Schmölzer, J. Pavelec , D. M. Fobes, J. Peng, Z. Q. Mao, G. Parkinson, M. Schmid, F. Mittendorfer, J. Redinger, and U. Diebold
Point Defects at Cleaved Sr(n+1)Ru(n)O(3n+1) (001) Surfaces
B. Stöger, M. Hieckel, F. Mittendorfer, Z. Wang, M. Schmid, G. S. Parkinson, D. M. Fobes, J. Peng, J. E. Ortmann, A. Limbeck, Z. Q. Mao, J. Redinger, and U. Diebold
High chemical activity of a perovskite surface: Reaction of CO with Sr3Ru2O7
B. Stöger, M. Hieckel, F. Mittendorfer, Z. Wang, D. Fobes, J. Peng, Z. Q. Mao, M. Schmid, J. Redinger, and U. Diebold
Cluster Nucleation and Growth from a Highly Supersaturated Adatom Phase: Silver on Magnetite
R. Bliem, R. Kosak, L. Perneczky, Z. Novotny, O. Gamba, D. Fobes, Z. Q. Mao, M. Schmid, U. Diebold, P. Blaha, and G. S. Parkinson
Ferro-Orbital Ordering Transition in Iron Telluride Fe(1+y)Te
D. Fobes, I. A. Zaliznyak, Z. Xu, R. Zhong, G. Gu, J. M. Tranquada, L. Harriger, D. Singh, O. Garlea, M. Lumsden, and B. Winn
Enhanced spin-triplet superconductivity near dislocations in Sr2RuO4
Y. A. Ying, N. E. Staley, Y. Xin, K. Sun, X. Cai, D. Fobes, T. J. Liu, Z. Q. Mao, and Y. Liu
From quasi-two-dimensional metal with ferromagnetic bilayers to Mott insulator with G-type antiferromagnetic order in Ca3(Ru(1-x)Ti(x))2O7
J. Peng, X. Ke, G. C. Wang, J. E. Ortmann, D. Fobes, T. Hong, W. Tian, X. S. Wu, and Z. Q. Mao
Unconventional quantum oscillations in mesoscopic rings of spin-triplet superconductor Sr2RuO4
X. Cai, Y. A. Ying, N. E. Staley, Y. Xin, D. Fobes, T. J. Liu, Z. Q. Mao, and Y. Liu
Effect of disorder on quantum phase transition in the double layered ruthenates (Sr(1-x)Ca(x))3Ru2O7
Z. Qu, J. Peng, T. J. Liu, D. Fobes, V. Dobrosavljevic, L. Spinu, and Z. Q. Mao
Ferromagnetism in CuFeSb: Evidence of competing magnetic interactions in iron-based superconductors
B. Qian, J. Lee, J. Hu, G. C. Wang, P. Kumar, M. H. Fang, T. J. Liu, D. Fobes, H. Pham, L. Spinu, X. S. Wu, M. Green, S. H. Lee, and Z. Q. Mao
Metal-insulator transition in doped Ca2RuO4: potential application in bolometric detection
D. Fobes, E. Vehstedt, G. C. Wang, T. J. Liu, Z. Q. Mao
Friedel-like Oscillations from Interstitial Iron in Superconducting Fe(1+y)Te0.62Se0.38
V. Thampy, J. Kang, J. A. Rodriguez-Rivera, W. Bao, A. T. Savici, J. Hu, T. J. Liu, B. Qian, D. Fobes, Z. Q. Mao, C. B. Fu, W. C. Chen, Q. Ye, R. W. Erwin, T. R. Gentile, Z. Tesanovic, and C. Broholm
Magnetic phase transitions and bulk spin-valve effect tuned by in-plane field orientation in Ca3Ru2O7
D. Fobes, J. Peng, Z. Qu, T. J. Liu, and Z. Q. Mao
From (pi, 0) magnetic order to superconductivity with (pi,pi) magnetic resonance in Fe1.02(Te(1-x)Se(x))
T. J. Liu, J. Hu, B. Qian, D. M. Fobes, Z. Q. Mao, W. Bao, M. Reehuis, S. A. J. Kimber, K. Prokes, S. Matas, D. N. Argyriou, A. Hiess, A. Rotaru, H. Pham, L. Spinu, Y. Qiu, V. Thampy, A. T. Savici, J. A. Rodriguez, and C. Broholm
Interplay between the lattice and spin degrees of freedom in (Sr(1-x)Ca(x))3Ru2O7
J. Peng, Z. Qu, B. Qian, D. Fobes, T. J. Liu, X. Wu, H. M. Pham, L. Spinu, and Z. Q. Mao
Anisotropy of magnetoresistivities in Sr4Ru3O10: Evidence for an orbital-selective metamagnetic transition
D. Fobes, T. J. Liu, Z. Qu, H. Q. Yuan, M. Salamon, M. Zhou, J. Hooper, and Z. Q. Mao
Doping and dimensionality effects on the core-level spectra of layered ruthenates
H. Guo, Y. Li, D. Urbina, B. Hu, R. Jin, T. Liu, D. Fobes, Z. Q. Mao, E. W. Plummer, and J. Zhang
Suppression of Proximity Effect and the Enhancement of p-Wave Superconductivity in the Sr2RuO4-Ru System
Y. A. Ying, Y. Xin, B. W. Clouser, E. Hao, N. E. Staley, R. J. Myers, L. F. Allard, D. Fobes, T. Liu, Z. Q. Mao, and Y. Liu
Charge carrier localization induced by excess Fe in the superconductor Fe(1+y)Te(1-x)Se(x)
T. J. Liu, X. Ke, B. Qian, J. Hu, D. M. Fobes, E. K. Vehstedt, H. Pham, J. H. Yang, M. H. Fang, L. Spinu, P. Schiffer, Y. Liu, Z. Q. Mao
Complex electronic states in double-layered ruthenates (Sr(1-x)Ca(x))3Ru2O7
Z. Qu, J. Peng, T. J. Liu, D. Fobes, L. Spinu, and Z. Q. Mao
Real-space observation of magnetic domain structure at metamagnetic tansition in a triple-layer ruthenate Sr4Ru3O10
Y. Nakajima, Y. Matsumoto, D. Fobes, M. Zhou, Z. Q. Mao, and T. Tamegai
Unusual heavy-mass nearly ferromagnetic state with a surprisingly large Wilson ratio in the double layered ruthenates (Sr(1-x)Ca(x))3Ru2O7
Z. Qu, L. Spinu, H. Yuan, V. Dobrosavljević, W. Bao, J. W. Lynn, M. Nicklas, J. Peng, T. Liu, D. Fobes, E. Flesch, and Z. Q. Mao
Band-Dependent Normal-State Coherence in Sr2RuO4: Evidence from Nernst Effect and Thermopower Measurements
X. Xu, Z. Xu, T. Liu, D. Fobes, Z. Mao, Y. Liu
Magnetic, electrical transport, and thermoelectric properties of Sr4Ru3O10: Evidence for a field-induced electronic phase transition at low temperatures
Z. Xu, X. Xu, R. Freitas, Z. Long, M. Zhou, D. Fobes, M. Fang, P. Schiffer, Z. Mao, and Y. Liu
Phase diagram of the electronic states of trilayered ruthenate Sr4Ru3O10
D. Fobes, M. H. Yu, M. Zhou, J. Hooper, C. J. O'Connor, M. Rosario, and Z. Q. Mao
Competing magnetic fluctuations in Sr3Ru2O7 probed by Ti doping
J. Hooper, M. H. Fang, M. Zhou, D. Fobes, N. Dang, Z. Q. Mao, C. M. Feng, Z. A. Xu, M. H. Yu, C. J. O'Connor, G. J. Xu, N. Andersen, and M. Salamon
Electronic and magnetic properties of triple-layered ruthenate Sr4Ru3O10 single crystals grown by a floating-zone method
M. Zhou, J. Hooper, D. Fobes, Z. Q. Mao, V. Golubb and C. J. O'Connor
Presentations
Invited: 11
Contributed: 21
Contributed: 21
25 June 2018
American Conference on Neutron Scattering
College Park, Maryland
Invited talk
Spin excitations of the skyrmion lattice in MnSi
9 August 2017
Skyrmionics: Materials, Phenomena and Applications
Santa Fe, New Mexico
Invited talk
Spin excitations of the skyrmion lattice in MnSi
17-21 July 2017
International Conference on Strongly Correlated Electron Systems (SCES)
Prague, Czech Republic
Poster
Magnetic frustration in a prototypical strongly correlated metal
9-13 July 2017
International Conference on Neutron Scattering (ICNS)
Daejeon, South Korea
Contributed talk
Magnetic frustration in a prototypical strongly correlated metal
7 June 2017
Science in '3'
Los Alamos National Laboratory, Los Alamos, NM
Contributed talk
Emerging Electronic Order from Frustrated Magnetism
14 March 2017
APS March Meeting
New Orleans, LA
Contributed talk
Magnetic frustration in a prototypical strongly correlated electron system
11 January 2016
LDRD External Project Review
Los Alamos National Laboratory, Los Alamos, NM
Neutron spectroscopy investigation of skyrmion lattice materials
2 November 2016
Triennial DOE-BES-MSE Review
Los Alamos National Laboratory, Los Alamos, NM
Poster
Neutron Spectroscopy Studies of CeRhIn5
11 July 2016
American Conference on Neutron Scattering
Long Beach, CA
Contributed talk
Magnetic frustration induced by applied magnetic field in CeRhIn5
14 March 2016
APS March Meeting
Baltimore, MD
Contributed talk
Spin wave spectrum of CeRhIn5 under applied magnetic field
4 March 2015
APS March Meeting
San Antonio, TX
Contributed talk
"Forbidden" phonon in the iron chalcogenide series
20 November, 2014
Young Researcher Symposium
Brookhaven National Laboratory, Upton, NY
Poster
Ferro-orbital order and unexpected phonon scattering in the iron chalcogenide superconductor family
12 November 2014
Los Alamos National Laboratory
Los Alamos, NM
Invited talk
Ferro-orbital order and 'forbidden' phonons in the iron chalcogenides
9 November 2014
Louisiana State University
Baton Rouge, LA
Invited talk
Ferro-orbital order and an unexpected phonon mode in the iron chalcogenide superconductor family
4 June 2014
American Conference on Neutron Scattering
Knoxville, TN
Contributed talk
Observation of an acoustic mode potentially driven by an imbalance between the magnetic moments of neighboring Fe atoms in Fe(1-x)Te (y < 0.12)
14 May 2014
Oak Ridge National Laboratory
Oak Ridge, TN
Invited Seminar
Bond order wave formation and an unexpected acoustic mode in iron-chalcogenide end-member Fe(1+y)Te revealed by neutron scattering studies
5 March 2014
APS March Meeting
Denver, CO
Contributed talk
Observation of acoustic-phonon-like mode driven by magnetic imbalance between neighboring Fe atoms in Fe(1+y)Te (y<0.12)
25 February 2014
QCMD Seminar Series at Oak Ridge National Laboratory
Oak Ridge, TN
Invited talk
Neutron scattering studies of the effects of non-stoichiometric interstitial Fe in iron-chalcogenide end-member Fe(1+y)Te
19 March 2013
APS March Meeting
Baltimore, MD
Contributed talk
Unconventional (pi, pi) order in Fe1.1Te
28 February 2012
APS March Meeting
Boston, MA
Contributed talk
Anisotropy of magnetoresistivities in Sr3Ru2O7: Evidence for orbital-dependent metamagnetism
13 October 2011
Brookhaven National Laboratory
Upton, NY
Invited Colloquium
Exotic phenomena in strongly correlated layered ruthenates
23 September 2011
Oak Ridge National Laboratory
Oak Ridge, TN
Invited Colloquium
Exotic phenomena in strongly correlated layered ruthenates
22 June 2011
Lawrence Livermore National Laboratory
Livermore, CA
Invited Colloquium
Exotic phenomena in strongly correlated layered ruthenates
23 March 2011
APS March Meeting
Dallas, TX
Contributed talk
Metastable Magnetic states in Ca3Ru2O7
8 July 2010
Tulane University
New Orleans, LA
Dissertation Defense
Orbital dependence of magnetism in layered ruthenate systems
19 March 2010
APS March Meeting
Portland, OR
Contributed talk
Anisotropic magnetic coupling in Ca3Ru2O7 probed by angle resolved magnetotransport
15 September 2009
Tulane University
New Orleans, LA
Invited Colloquium
Orbital Physics in Layered Ruthenates
21 May 2009
Tulane University
New Orleans, LA
Prospectus Defense
Probing the orbital dependence of magnetic phenomena in layered ruthenate systems
19 March 2009
APS March Meeting
Pittsburgh, PA
Contributed talk
Probing orbital-dependent magnetism in layered perovskite ruthenates through angle-dependent magnetoresistivity
14 March 2008
APS March Meeting
New Orleans, LA
Contributed talk
Anisotropy of magnetoresistivity in trilayered ruthenate Sr4Ru3O10: Evidence for orbital dependent metamagnetism
5 March 2007
APS March Meeting
Denver, CO
Contributed talk
Competing magnetic fluctuations in Sr3Ru2O7 probed by Ti doping
10 April 2006
Tulane University
New Orleans, LA
Seminar