To conduct high level multidisciplinary research in experimental and theoretical condensed matter physics and in materials science. To synthesize and characterize novel advanced materials and study their electronic and magnetic properties using most modern techniques such as all kind of neutron and high resolution X-ray scattering. Systems of interest include molecular solids such as fullerenes, solid cubane and high temperature ceramics such as magnetic cuprates and perovskites. The cubane system, for example, offers promise in many technologically important applications as diverse as anti-viral agents, explosives, and fuel additives.

• Staff physicist:1997-present
  NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland.
• PostDoc.:1994-1997
  University of Maryland and National Institute of Standards and Technology, Maryland.
• PhD:1990-1994
  Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania.
  Thesis: Theoretical and experimental study of solid C and its Na-doped derivatives and also quantum magnetism and magnetic structures of lamellar perovskite antiferromagnets.
  Thesis Advisor : Prof. A. B. Harris and Prof. J. Fischer
• MSc:1988-1990
  Department of Physics, Middle East Technical University, Ankara, Turkey.
  Thesis: Electron-phonon interactions in low dimensionally confined quantum well type semiconductors.
  Thesis Advisor: Prof. Atilla Ercelebi
• BS :1985-1988
  Department of Physics, Middle East Technical University, Ankara, Turkey.
  
• High School :1982-1985
  Ankara Fen Lisesi, Ankara, Turkey.

• Member, American Physical Society (APS).
• 1994 Complimentary membership, Materials Research Society (MRS).
• Member, Electrochemical Society (ECS).

• 1993 Materials Research Society Award: In recognition of outstanding performance in the conduct of research
• Invited Talk at the March 1994 APS Meeting, Pittsburgh, Pennsylvania.
• Invited Talk at International Winterschool on Electronic Properties of Novel Materials, Kirchberg/Tirol, AUSTRIA 1994.
• Invited Lecture at EUROCONFERENCE on Novel Superconducting Materials, Pisa, Italy, January 1996.
• Invited talk at Electrochemical Society Meeting, Los Angeles, California, May 1996.
• Invited talk at the March 1997 APS Meeting, Kansas City, MO.

• Two week visit at the University of Montpellier, France; to perform NMR studies of Na-doped fullerenes.
• 10 day visit at at the University of Vienna, Austria; to perform Raman experiments.
• One week visit at the Ohio University, Athans, OH; to study the polymer phase of KC .

• My most recent major accomplishment is the first characterization of the orientationally disordered phase of solid cubane using X-ray and neutron scattering. This work is very important as understanding the phase equilibria is the first fundamental step towards understanding the nature of this important system. Cubane is the most highly strained, kinetically stable ring system available in quantity, and therefore offers promise in many diverse and interesting practical applications as anti-viral agents, explosives, high-refractive index lenses, specialty polymers, and fuel additives.

• First synthesis and characterization of the saturated phase of the Na-C system: intercalation of heteroclusters into solid C . (See T.Yildirim et al. Nature, 350, 568 (1992)). This discovery had a big impact as it changed the way we looked at the intercalation of fullerene compounds. It suggests that using smaller alkali metals such as Li, one can intercalate even more atoms than Na into the lattice, which is of interest and the primary goal of the alkali-battery research. I have been recognized for this work by winning the Materials Research Society Award In recognition of outstanding performance in the conduct of research and I have been invited to give many talks and received offers of collaboration.

• One of the major impacts of my combined theoretical, synthetic and experimental work is for the first time to provide a unified view of orientational ordering in pristine and alkali-intercalated solid C . (See T.Yildirim et al. Phys. Rev. Lett. 71, 1383 (1993)). This work made it possible for the whole fullerene community to begin to understand the influence of molecular orientational order/disorder phenomena on properties such as superconductivity. I have been extensively recognized for this work by an invited talk at the American Physical Society March Meeting in 1994, an invitation to a small prestigious workshop on fullerenes held in Austria 1994, and numerous offers of collaborations from research groups all over the world.

• Discovery and extensive studies of two novel families of fullerides: Na CsC and M BaC , which for the first time enable us to study the correlation between the superconducting transition temperature and the carrier concentration. (See T. Yildirim et al Phys. Rev. Lett. 77, 167 (1996)). This work had a very big impact on community of fulleride superconductivity as it underscores the failure of many previous works on the theory of superconductivity in fullerenes and clearly demonstrate that the true mechanism of superconductivity in these systems is quite different than that in the high T cuprates, and is very unique. Invitations to the Euroconference on novel superconductor materials, Pisa, Italy (Jan. 1996), to Electrochemical Society Meeting in Los Angeles (May 1996) and many other invited talks at universities and labs are some of the indications that I have been recognized for this work again by a large number of scientists in the field of condensed matter, materials science, and solid state chemistry.

• First to demonstrate that the spin Hamiltonian of the tetragonal lamellar antiferromagnets (which exhibit high temperature superconductivity after doping, and thus are technologically very important materials) contains several novel anisotropies (See T. Yildirim et al, Phys. Rev. Lett. 72, 3710 (1994)). Using these anistropic interactions, we developed a theory that successfully explains the three dimensional magnetic structure. Currently we are generalizing our theory by including other interactions, such as the single-ion anisotropy generated by crystal-field in rare earths like Nd, to explain the recently observed non-collinear spin structure and the three consecutive magnetic transitions in Nd CuO .

• Developed a theory which for the first time corrects, extends, and clarifies results concerning the spin Hamiltonian used to describe the ground manifold of Hubbard models for magnetic insulators in the presence of spin-orbit interactions. (See T. Yildirim et al, Phys. Rev. Lett. 73, 2919 (1994)). The biggest impact of this work is the demonstration that almost all previous work which invoked the orthorhombic distortion to explain the observed anisotropy (causing the spins to lie in the Cu-O plane) are wrong. Our theory clearly shows that this anisotropy is due to spin-orbit and Coulomb exchange interactions and independent of distortion. Our theory has been confirmed by recent experiments which indeed show the same anisotropy in tetragonal cuprates which have no orthorhombic distortion. I have been invited to many labs, including NEC and IBM, to give seminars on this work.

• Dr. Sam Trevino (US Army)
• Dr. Dan Neumann, Dr. Jeff Lynn (NIST)
• Prof. J. E. Fischer, Prof. A. B. Harris, Prof. E. Mele (Univ. of Pennsylvania)
• Prof. P. W. Stephens (SUNY-Stony Brook&Brookhaven National Laboratory)
• Prof. Ron Cappelletti (Ohio University)
• Prof. C. L. Lin (Temple University, PA)
• Prof. E.F.Shender (Univ. of CA, Berkeley)
• Dr. E. Schirber (Sandia Labs)
• Dr. S. Erwin (Naval Research Laboratory)
• Dr. T.T.M. Palstra (At&T Bell Labs)
• Prof. H. Kuzmany (University of Vienna)
• Prof. Amnon Aharony, Prof. O.Entin-Wohlman (Tel Aviv University, Israel)
• Dr. P. Petit (CNRS-ULPO, France)
• Dr. F. Rachdi (GDPC Montpellier, France)

• Experimental Skills:
  • Specialized in X-ray powder diffraction using both the INEL-diffractometer and the NSLS synchrotron X-ray at Brookhaven National Laboratory.
  • Experience in various neutron scattering techniques such as powder and single crystal diffraction on both magnetic and non-magnetic samples, time-of flight measurements (TOF), quasielastic and inelastic neutron scattering (both coherent and incoherent).
  • Specialized in ab initio structure characterization from both X-ray and neutron data using Rietveld refinement (GSAS).
  • Specialized in solid state synthesis including intercalation and high temperature ceramics as well as single crystal growing (e.g. Sr CuCl O ).
  • Good knowledge of thermal analysis (such as DSC, MDSC), magic angle spinning (MAS) solid state NMR, and Raman scattering on powder samples.
  • Experience in glove box and vacuum line manipulations of air-sensitive materials.
• Theoretical Skills:
  • Extensive computer programming, mostly using Fortran. Have a good knowledge of UNIX, DOS, etc.
  • Experience in first principle calculations of the structures of molecules such as C and cubane using Gaussian 94 package.
  • Experience in ab initio calculations of the intermolecular interactions, crystal structure, and other properties such as compressibility of molecular solids using the Gordon-Kim approach.
  • Specialized in lattice dynamics and crystal structure calculations based on phenomenological potential models.
  • Specialized in the calculation of the effects of quantum fluctuations on the ground state properties of frustrated magnetic systems such as BCT,FCC and kagome antiferromagnets. Tools are 1/S expansion, interacting and non-interacting spin waves, perturbation theory and exact numerical diagonalization.
  • Specialized in the derivation of macroscopic spin Hamiltonians for magnetic materials starting from a multi-band Hubbard model in the presence of spin-orbit and Coulomb exchange interactions. Tools are degenerate perturbation theory, exact numerical diagonalization on small clusters, etc.
  • Specialized in calculation of spin structures, inelastic neutron scattering intensity calculations, crystalline electric field (CEF) calculations for rare-earth cuprates, and many other systems.

• 1988 - 1990: Instructor, Department of Physics, METU, Ankara, Turkey
  
  Duties included teaching Physics courses for the first year undergraduate students, organizing labs, grading exams and homeworks, recitation, and holding office hours.
• 1990 - 1992: Teaching Assistant, Department of Physics, University of Pennsylvania
  
  Duties included grading advanced graduate level courses such as particle physics, advanced solid state physics, and quantum mechanics, teaching and organizing 2nd and 3rd year undergraduate laboratories such as Experiments in Modern Physics, facileting tutoring sessions and providing academic counseling to college students.
• 1992 - 1994: Research Assistant, Department of Physics, University of Pennsylvania
  
  Duties included conducting independent research in the field of condensed matter physics and materials science, synthesizing new advanced materials and characterizing them using modern techniques such as synchrotron X-ray diffraction at Brookhaven National laboratory.
• 1994 - Present Post-doctoral research position at University of Maryland and National Institute of Standards and Technology
  
  Duties include conducting independent research to solve outstanding problems in materials science and in experimental and theoretical solid state physics, developing theories to improve our understanding of the structure and dynamics of novel advanced materials, discovering new high-tech. materials, which will have technological applications, applying neutron scattering techniques to materials science using the research facilities at reactor radiation division, National Institute of Standards and Technology.

• Born: 04/ 15/ 1968 - Kars, Turkey
• Nationality: TURKISH and Permanent Resident of US
  based on the E11 category Alien of Extraordinary Ability in Sciences
• Married: Emel Yildirim (Turkish and Permanent Resident of US)