If you are having trouble figuring which one is me, there are more pictures here.

For those of you considering a career in physics, we are pleased to have,
exclusively on this website, a handy brochure on what a physicist does all day.
Thanks to the author, Megan Buchanan.

Jamil Tahir-Kheli, PhD

Publications

Senior Staff Scientist
Materials and Process Simulation Center
California Institute of Technology
Beckman Institute 139-74
Pasadena, CA 91125 USA
You can write to me by clicking here.
I am a US citizen

I entered Oxford to read Maths when I was 15 and received my Physics PhD in this group in 1992. My thesis work was on high temperature cuprate superconductivity. In particular, I studied the standard three-band Hubbard models. After spending one year after my degree doing a postdoc and thinking a lot about the experimental data, I became convinced that there was possibly a missing electronic component necessary to understand the hightc mechanism. Given there was not much funding available to persue a different direction in cuprates, I left Caltech.

I consulted in industry for 8 years before returning to the group in 2001. This was probably the best thing that happened to me. I was lucky enough to work on some fun projects during this time that opened my eyes to solving practical problems. Some of the projects I worked on are:

  1. financial modelling of a $2.5 billion US stock portfolio,
  2. modelling the fluid flow of a novel medical device that led to FDA approval of the product,
  3. signal processing for Synthetic Aperature Radar (SAR).
During this time, I worked closely with Dr. Jason Perry to understand if an additional electronic component made sense for the cuprates. We were able to argue that the missing orbital was out-of-plane and arose through application of the current state-of-the-art density functionals used in chemistry (B3LYP). The important difference between B3LYP and prior functionals applied to the cuprates was the inclusion of exact Hartree-Fock exchange (so-called hybrid DFT functionals). The functionals were developed in the early 90's and were not available during the late 80's when the band structure calculations of the cuprates were performed.

I am sure you are getting bored reading this so I will speed up. I returned to the Goddard group in 2001. We were able to show that out-of-plane character arose from doping in LaSrCuO. We published a PRB paper in July 2007 that incorporates out-of-plane character into a theory for the cuprates.

My current research interests include:

  1. high figure of merit (ZT) thermoelectrics. In collaboration with the Heath group, we recently developed a new theory to explain the approximately 100-fold increase in the ZT of Silicon nanowires from ZT~0.14 for bulk Si to ZT~1 for a 10 x 20nm p-type wire. Science had a writeup (Sept. 7, 2007 vol. 317, pp 1318) about the work. Nature published our paper (10 January, 2008) along with a News and Views article describing the work.

    My contribution was the theory where two important discoveries were made:

    First, we showed that phonon drag thermopower can reappear for small nanowires contrary to a generation of theory and experiment "proving" this is impossible.

    Second, the so-called "Slack's minimum thermal conductivity" for Si is not a lower bound when a three-dimensional to one-dimensional crossover for phonon modes occurs in the smallest nanowires.

  2. high temperature superconductivity. I believe my recent paper has the missing electronic component necessary to properly understand these materials. Perhaps my recent thermoelectric Nature paper will help remove the crackpot label hanging over my head and I will be invited to give some seminars!

    I am reminded of the Linus Pauling quote during the 1954 Nobel ceremonies:

    "Perhaps as one of the older generation, I should preach a little sermon to you, but I do not propose to do so. I shall, instead, give you a word of advice about how to behave toward your elders. When an old and distinguished person speaks to you, listen to him carefully and with respect--but do not believe him. Never put your trust in anything but your own intellect. Your elder, no matter whether he has gray hair or has lost his hair, no matter whether he is a Nobel laureate, may be wrong. So you must always be sceptical--always think for yourself."

    Given the large number of distinguished theorists and theories in this field, it is obvious they all cannot be right. Maybe, just maybe, none of them are right. Perhaps after 20 years, there should be some openess to some new approaches.......

    I am aware Pauling was a chemist and chemists are not considered experts in cuprate superconductivity. A Nobel laureate physicist once said to me that chemists don't really understand what a phase transition is. I think his implication was that since hightc is going to end up being driven by a quantum critical point, all chemists are out of their league. Mind you, I am in the Caltech chemistry department and it is possible I simply don't understand his deep thoughts!

    If you have any opinions (postive or negative) you would like to share, please send me an email (jamil atsign wag dot caltech dot edu).

  3. ab-initio electronic structure and transport.
  4. applications of above to I-V characteristics in nanoelectronic and molecular devices.

EDUCATION:

Ph. D., Physics, California Institute of Technology, Pasadena, CA (1992)
M.S., Physics, California Institute of Technology, Pasadena, CA (1986)
M..A. Oxon (Honorary), Oxford University, Oxford, England (1993)
B.A. Honours, First Class, Mathematics, Oriel College, Oxford University, Oxford, England (1984)

PROFESSIONAL EXPERIENCE:

May 2001-present
Senior Staff Scientist, Materials and Process Simulation Center, California Institute of Technology
1994-2001
Consultant, First Principles Research, Inc., Los Angeles, CA
1993-1994
Research Associate, First Quadrant, Inc., Pasadena, CA
1992-1993
Postdoctoral Fellow, California Institute of Technology, Pasadena, CA

PUBLICATIONS:

    ChiYung Yam, Yan Mo, Fan Wang, Xiaobo Li, GuanHua Chen, Xiao Zheng, Yuki Matsuda, Jamil Tahir-Kheli, William A. Goddard III, "Equivalent electric circuit of a carbon nanotube based molecular conductor," http://arxiv.org/abs/0801.3914 (submitted)

    Akram I. Boukai, Yuri Bunimovich, Jamil Tahir-Kheli, Jen-Kan Yu, William A. Goddard III, and James R. Heath, "Silicon nanowires as highly efficient thermoelectric materials," NATURE 451, 168 (2008). (link) News and Views

    Jamil Tahir-Kheli and W.A. Goddard III, "Chiral plaquette polaron theory of cuprate superconductivity," PHYS. REV. B 76, 014514 (2007).

    Y.H. Kim, Jamil Tahir-Kheli, P.A. Schultz, and W.A. Goddard III, "First-principles approach to the charge-transport characteristic of monolayer molecular-electronics devices: Application to hexanedithiolate devices," PHYS. REV. B 73, 235419 (2006).

    Jamil Tahir-Kheli, M. Miyata, and W. A. Goddard III, "Dielectric breakdown in SiO2 via electric field induced attached hydrogen defects," MICROELECTRONIC ENGINEERING 80, 174 (2005).

    Y. Gilman, P.B. Allen, Jamil Tahir-Kheli, and W. A. Goddard III, "Numerical resistivity calculations for disordered three-dimensional metal models using tight-binding Hamiltonians," PHYS. REV. B 70, 224201 (2004).

    Jason K. Perry, Jamil Tahir-Kheli, and William A. Goddard III, "Ab Initio Evidence for the Formation of Impurity d(3z2-r2) Holes in Doped La2-xSrxCuO4," PHYS. REV. B 65, 144501 (2002).

    Jason K. Perry, Jamil Tahir-Kheli, and William A. Goddard III, "Antiferromagnetic Band Structure of La2CuO4: Becke-3-Lee-Yang-Parr Calculations," PHYS. REV. B 63, 144510 (2001).

    Jamil Tahir-Kheli, "The NMR of High Temperature Superconductors without Anti-Ferromagnetic Spin Fluctuations," J. PHYS. CHEM A. 104, 2432 (2000).

    Jason K. Perry and Jamil Tahir-Kheli, "Electronic Structure of La_(1.85)Sr_(0.15)CuO_4: Characterization of a Fermi Level Band Crossing," PHYS. REV. B 58, 12323 (1998).

    Jamil Tahir-Kheli, "Interband Pairing Theory of Superconductivity," PHYS. REV. B 58, 12307 (1998).

    Jamil Tahir-Kheli, "Inter-Band Pairing: Resolution of Observed S and D-Wave Tunneling with Isotropic S-Wave Pairing," in "Proceedings of the 10th Anniversary HTS Workshop on Physics, Materials and Applications," ed. B. Batlogg, C.W. Chu, W.K. Chu, D.U. Gubser, and K.A. Muller (World Scientific, New Jersey: 1996), 491-492.

    Jamil Tahir-Kheli and William A. Goddard III, "The Infinite Range Heisenberg Model and High Temperature Superconductivity," PHYS. REV. B 48, 13002 (1993).

    Jamil Tahir-Kheli and W. A. Goddard III, "Spinons and Holons in 1-D Three-Band Hubbard Models for High T_c Superconductors," PROC. NAT. ACAD. SCI. 90, 9959 (1993).

    Jamil Tahir-Kheli and William A. Goddard III, "Exact Solution to a Strongly Coupled Hubbard Model in 1-D for High T_c Superconductors," PHYS. REV. B 47, 1116 (1993).