Christopher C. Homes

 

Physicist, SXSS Group

Infrared and Terahertz Spectroscopy

 

Fellow, American Physical Society

 

NSLS II - Bldg. 741

Brookhaven National Laboratory

740 Brookhaven Avenue

P.O. Box 5000

Upton, NY 11973-5000

 

Tel: (631) 344-7579

Fax: (631) 344-2739

email: homes@bnl.gov

 

Curriculum vitae

 

Welcome to my personal home page! I am a physicist in the Soft X-ray Scattering & Spectroscopy (SXSS) at the NSLS II at Brookhaven National Laboratory, where I study the interaction of light with solids, and pretty much anything else too slow to get out of the way.  If you would like to learn more about the fundamentals of infrared spectroscopy, you can view a PDF file of a monograph Fourier-transform infrared spectroscopy (recently revised) that I am working on, but have not yet finished (you will need Adobe Acrobat Reader to view this document). By the way, the picture on the screen is a part of the Fermi surface of the perfectly-compensated semimetal WTe₂, a colossal magnetoresistance material.

• Biographical sketch (PDF)

• Research interests & experimental program

• Full publication list (selected publications)

• Comscope

• Spectrum project

• Useful links

• Personal musings

 

Education, professional experience

• B.Sc. (Hons.) summa cum laude, McMaster University ('83)

• M.Sc., Ph.D., University of British Columbia ('85,'90)

• Postdoc., McMaster ('90-'92)

• NSERCC Postdoc. & Research Assoc., Simon Fraser University ('92-'96)

• Asst. Physicist, BNL ('96-'98)

• Assoc. Physicist, BNL ('98-'01)

• Physicist, BNL ('01-present, granted tenure in '03)

• Visiting Professor (Paris VI), Laboratoire Photons et Matière, ESPCI ('07)

Honours and awards

• NSERCC Postdoctoral Fellowship ('92)

• Brookhaven Science and Technology Award ('07)

• Fellow, American Physical Society ('08)

 

Research Interests & Experimental Program

 

I am primarily interested in using infrared radiation to probe the electronic and vibrational properties of solids. The reflectance of a material is a complex quantity, with an amplitude and a phase. During a typical experiment, we only measure the reflected amplitude of the radiation. However, if the reflectance is measured over a wide enough range, then it is possible using the Kramers-Kronig relation to calculate the phase: once the amplitude and phase are known, then other optical response functions may be calculated, specifically the real part of the complex conductivity. 

 

The current focus of my research is strongly correlated electron systems, with special attention on systems that show emergent behavior, such as the cuprate, and more recently the iron-based, superconductors.  I am also interested in the Dirac and Weyl semimetals; recent work has also included the colossal thermopower material FeSb_2. We have extended our infrared techniques well into the terahertz region (1 THz = 33.3 cm^-1), allowing the low-energy collective modes of these systems to be studied. 

• Pseudogap in the underdoped cuprate superconductors

• Charge- and spin-stripe order in transition metal oxides

• Iron-based superconductors

• Dirac and Weyl semimetals

• Colossal magentoresistance and thermopower materials

• First principle methods for determining electronic strucure and lattice vibrations

Much of our current work is on the iron-based superconductors.  ARPES and density functional theory both indicate that the iron-based materials are multiband systems with electron and hole pockets; we therefore approach the conductivity using the so-called "two-Drude" model to extract the temperature dependence of the two different types of carriers; allowing hidden non-Fermi liquid behavior to be studied.   I am also involved with the validation component in the Center for Computational Material Spectroscopy and Design (Comscope).

 

 

 

Recent Publications (full publication list)

• Fate of quasiparticles in the superconducting state, S. V. Dordevic, D. van der Marel, and C. C. Homes, Phys. Rev. B 90, 174508 (2014).

• Optical conductivity of nodal metals, C. C. Homes, J. J. Tu, J. Li, G. D. Gu and A. Akrap, Sci. Rep. 3, 3446 (2013).

• Hidden T-linear scattering rate in Ba_0.6K_0.4Fe₂As₂, Y. M. Dai, B. Xu, B. Shen, H. Xiao, H. H. Wen, X. G. Qiu, C. C. Homes, and R. P. S. M. Lobo, Phys. Rev. Lett. 111, 117001 (2013).

• Doping for superior dielectrics, C. C. Homes and T. Vogt, Nature Mater. 12, 782 (2013).

• Do organics and other exotic superconductors fail universal scaling relations? S. V. Dordevic, D. N. Basov, and C. C. Homes, Sci. Rep. 3, 1713 (2013).

• n_s-T_c correlations in granular superconductors, Y. Imry, M. Strongin and C. C. Homes, Phys. Rev. Lett. 109, 067003 (2012).

• Determination of the optical properties of La_2-xBa_xCuO₄ for several dopings, including the anomalous x=1/8 phase, C. C. Homes, M. Hücker, Q. Li, Z. J. Xu, J. S. Wen, G. D. Gu, and J. M. Tranquada, Phys. Rev. B 85, 134510 (2012).

• Electronic correlations and unusual superconducting response in the optical properties of the iron chalcogenide FeTe_0.55Se_0.45, C. C. Homes, A. Akrap, J. S. Wen, Z. J. Zu, Z. W. Lin, Q. Li, and G. D. Gu, Phys. Rev. B 81, 180508(R) (2010).

• Infrared phonon anomaly in BaFe₂As₂, A. Akrap, J. J. Tu, L. J. Li, G. H. Cao, Z. A. Xu, and C. C. Homes, Phys. Rev. B 80, 180502(R) (2009).

Book Chapters

• Instrumentation for far-infrared spectroscopy, P. R. Griffiths and C. C. Homes, Handbook of Vibrational Spectroscopy, Volume 1 - Theory and Instrumentation (Wiley, New York, 2001).

• The infrared conductivities of semiconducting (TMTSF)₂ReO₄ and (TMTSF)₂BF₄, compared with several model calculations, C. C. Homes and J. E. Eldridge, Organic Superconductivity, edited by V. Z. Kresin and W. A. Little (Plenum Press, New York, 1990), pp. 89-98.

Other notable works...

• Silicon beam splitter for far-infrared and terahertz spectroscopy, C. C. Homes, G. L. Carr, R. P. S. M. Lobo, J. D. LaVeigne, and D. B. Tanner, Appl. Opt. 46, 7884 (2007).

• Scaling laws in high-temperature superconductors as revealed through infrared spectroscopy, C. C. Homes, Synchrotron Radiation News 18, 9-14 (2005).

• A universal scaling relation in high-temperature superconductors, C. C. Homes, S. V. Dordevic, M. Strongin, D. A. Bonn, Ruixing Liang, W. N. Hardy, Seiki Komiya, Yoichi Ando, G. Yu, N. Kaneko, X. Zhao, M. Greven, D. N. Basov and T. Timusk, Nature 430, 539-541 (2004).

• Phonon screening in high-temperature superconductors, C. C. Homes, A. W. McConnell, B. P. Clayman, D. A. Bonn, Ruixing Liang, W. N. Hardy, M. Inoue, H. Negishi, P. Fournier, and R. L. Greene, Phys. Rev. Lett. 84, 5391-5394 (2000).

• Optical response of high-dielectric-constant perovskite-related oxide, C. C. Homes, T. Vogt, S. M. Shapiro, S. Wakimoto, and A. P. Ramirez, Science 293, 673-676 (2001).

• Synchrotron infrared photoacoustic spectroscopy, Kirk. H. Michaelian, Richard S. Jackson, and Christopher C. Homes, Rev. Sci. Inst. 72, 4331-4336 (2001).

• Optical properties along the c-axis of YBa₂Cu₃O_6+x, for x=0.5 to 0.95: evolution of the pseudogap, C. C. Homes, T. Timusk, Ruixing Liang, D. A. Bonn, and W. N. Hardy, Physica C 254, 265-280 (1995). The original paper contains an error in Fig. 2; the corrected figure is shown in  erratum in Physica C 432, 316 (2005).

• Optical phonons polarized along the c-axis of YBa₂Cu₃O_6+x, for x=0.5 to 0.95, C. C. Homes, T. Timusk, D. A. Bonn, Ruixing Liang, and W. N. Hardy, Can. J. Phys. 73, 663-675 (1995).

• Optical properties along the c-axis of YBa₂Cu₃O_6.70: evidence for a pseudogap, C. C. Homes, T. Timusk, Ruixing Liang, D. A. Bonn, and W. N. Hardy, Phys. Rev. Lett. 71, 1645-1648 (1993).

• Technique for measuring the reflectance of irregular, submillimeter-sized samples, C. C. Homes, M. Reedyk, D. A. Crandles, and T. Timusk, Appl. Optics 32, 2976-2983 (1993).

• The optical conductivity of the stable icosahedral quasicrystal Al_63.5Cu_24.5Fe₁₂, C. C. Homes, X. Wu, T. Timusk, Z. Altounian, A. Sahnoune, and J. O. Strom-Olsen, Phys. Rev. Lett. 67, 2694-2696 (1991).

 

Useful links

 

BNL and NSLS Infrared links:

• National Synchrotron Light Source

• U10A infrared beamline (decomissioned)

• Infrared users group

• Brookhaven National Laboratory

• Department of Energy (DOE)

• Office of Basic Energy Sciences (BES)

Physics related links:

• American Physical Society 

• Bruker Optics (USA)

Optics and superconductivity links:

• ISTEC

• McMaster University Infrared Group

• Spectroscopy Group, UCSD (Basov)

• Superconductivity

• UBC Superconductivity Group

• Optical properties of Solids (Wooten)

 

Personal Musings (a joke, as told by Bob Dynes)

 

A man in a hot air balloon realized he was lost.  He reduced altitude and spotted a woman below. He descended a bit more and shouted, "Excuse me, can you help me? I promised a friend I would meet him an hour ago, but I don't know where I am."

The woman below replied, "You're in a hot air balloon hovering approximately 30 feet above the ground. You're between 40 and 41 degrees north latitude and between 59 and 60 degrees west longitude."

"You must be an physicist," said the balloonist. "I am," replied the woman, "How did you know?"

"Well," answered the balloonist, "everything you told me is, technically correct, but I've no idea what to make of your information, and the fact is I'm still lost. Frankly, you've not been much help at all. If anything, you've delayed my trip."

The woman below responded, "You must be in Management." "I am," replied the balloonist, "but how did you know?"

"Well," said the woman, "you don't know where you are or where you're going. You have risen to where you are due to a large quantity of hot air. You made a promise which you've no idea how to keep, and you expect people beneath you to solve your problems. The fact is you are in exactly the same position you were in before we met, but now, somehow, it's my fault."