Christopher C. Homes

 

Physicist, Electron Spectroscopy Group

(Infrared and Terahertz Spectroscopy)

 

Fellow, American Physical Society

 

Condensed Matter Physics & Materials Science Dept. - Bldg. 510B

Brookhaven National Laboratory

20 Pennsylvania Street

P.O. Box 5000

Upton, NY 11973-5000

 

Tel: (631) 344-7579

Fax: (631) 344-2739

email: homes@bnl.gov

 

Welcome to my personal home page! I am a physicist in the Electron Spectroscopy Group in the Condensed Matter Physics and Materials Science Department 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. In particular, I use infrared radiation from conventional black-body sources, as well as from the National Synchrotron Light Source at the U12IR beam line. 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). I was once (but no longer am) involved with a software company called Idelix that developed advanced interface technologies, providing enhancements in mobile, desktop, Web-based applications, and is based in Vancouver, British Columbia; this company has since been reconstituted and is now known as Lat49. Finally, a link to the old picture that used to be here of our cat Kira helping me with a physics problem.

• Biographical sketch (PDF)

• Research interests & experimental program

• Full publication list (selected publications)

• Spectrum project

• Useful links

• Personal musings

• Images

 

Education, professional experience

• B.Sc. (Hons.), 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-'03)

• Physicist (tenure), BNL ('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.  In the past I have used this technique to study a wide variety of materials, including the low-dimensional organic conductors and superconductors, quasicrystals, C₆₀, collosal magnetoresistance materials (CMR's), high-dielectric response materials and the high-temperature cuprate superconductors. 

 

The current focus of my research is on electronic phenomena in strongly correlated electron systems.  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.  Of particular interest are

• High-temperature copper-oxide superconductors, e-doped analogs

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

• The new iron-arsenic superconductors

My current projects involve examining the polarized optical properties detwinned single crystals of  YBa₂Cu₃O_6+x (YBCO) at a variety of doping levels in the normal and superconducting states, with particular emphasis placed on the underdoped region.  The original high-temperature superconductor La_2-xBa_xCuO₄ (LBCO) material is also being studied for several chemical dopings, including the magic x~1/8 concentration, where the critical temperature is observed to be strongly suppressed due to the formation of charge- and spin-stripe order; the notion of competing order parameters is also being examined in the nickelate La₂NiO_4+d and the Sr_14-xCa_xCu₂₄O₄₁ two-leg ladder systems, as well as in the simpler Sr₂CuO₃ quasi-one dimensional material.  The electron-doped systems (Nd,Pr)_2-xCe_xCuO₄ are also being studied to determine of electron-hole symmetry exists within the cuprates, as well as if the underdoped region of the phase diagram, which is rather difficult to achieve in the electron-doped materials, is similar to that of the hole-doped materials.  In all of the infrared studies, we are also trying to develop methods of determining the spectral function and to compare it with information about the spectral function that may be determined from ARPES studies of these materials.

 

We are also interested in optical properties of ultra-thin films of Pb and in solvated-electron systems. This type of experiment blends ultra-high vacuum, low temperature, and optical techniques to grow a film in situ at cryogenic temperatures and measure the optical properties simultaneously. These studies are providing information about the nature of transport in disordered granular systems.  Future work in this area may also involve work on graphene.

 

 

Recent Publications (full publication list)

• 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).

• 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).

• Charge Order, Metallic Behavior, and Superconductivity in La_2-xBa₂CuO₄ with x=1/8, C. C. Homes, S. V. Dordevic, G. D. Gu, Q. Li, T. Valla, and J. M. Tranquada, Phys. Rev. Lett. 96, 257002, 1-4 (2006).

• 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).

• Sum rules and energy scales in the high-temperature superconductor YBa₂Cu₃O_6+x, C. C. Homes, S. V. Dordevic, D. A. Bonn, Ruixing Liang, and W. N. Hardy, Phys. Rev. B 69, 024514 (2004).

• 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).

• Unconventional energetics of the pseudogap state and superconducting state in high-Tc cuprates, D. N. Basov, C. C. Homes, E. J. Singley M. Strongin, T. Timusk, G. Blumberg, and D. van der Marel, Phys. Rev. B 63, 134514 (2001).

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

Book Chapters

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

Other notable works...

• 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 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). (zipped postscript)

• 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)

• U12IR infrared beamline

• IR home page

• Infrared users group

• Brookhaven National Laboratory

• Department of Energy (DOE)

• Office of Basic Energy Sciences (BES)

Physics related links:

• American Physical Society 

• Bruker Optics (Germany)

• Bruker Optics (USA)

Optics and superconductivity links:

• Center for Superconductivity Research (Maryland)

• High-Tc Update

• ISTEC

• McMaster University Infrared Group (Timusk)

• Spectroscopy Group, UCSD (Basov)

• Superconductivity

• UBC Superconductivity Group (Bonn & Hardy)

 

Personal Musings

 

Whenever you advise a ruler in the way of the Tao,
Counsel him not to use force to conquer the universe.
For this would cause resistance.
Thorn bushes spring up wherever the army has passed.
Lean years follow in the wake of a great war.
Just do what needs to be done.
Never take advantage of power.

Achieve results,
But never glory in them.
Achieve results,
But never boast.
Achieve results,
But never be proud.
Achieve results,
Because this is the natural way.
Achieve results,
But not through violence.

Force is followed by loss of strength.
This is not the way of the Tao.
That which goes against the Tao
comes to an early end.

Lao Tsu, Tao Te Ching (Thirty)

 

  

Last modified: Monday, May 16, 2011 02:26 PM.