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Superconductors Get a Boost from Pressure PDF Print E-mail
Since the discovery in 1986 of high-temperature superconductivity in layered cuprates, the secrets of this remarkable phenomenon have steadily emerged. From the time of the earliest reports, it has been well recognized that the superconducting transition temperature is highly sensitive to the level of chemical doping, a necessary prerequisite to attaining the superconducting state in these materials. As a method of investigating the fundamental changes in physical properties characteristic of the superconducting state, however, doping is a rather coarse probe because a continuous variation in dopant concentration is difficult to achieve. Tanja Cuk, then a graduate student at Stanford University, together with colleagues from Carnegie, the University of Waterloo, the Naval Research Laboratory, and the Nanoelectronics Research Institute (Japan) found for the first time that in addition to chemical manipulation, the superconducting state can be induced by applied pressure in high temperature, cuprate superconductors, as it has been for low-temperature, elemental superconductors. Using the Raman spectroscopy laboratory at Carnegie and the high-pressure synchrotron x-ray beamline at HPCAT, both CDAC-supported facilities, Cuk and colleagues have applied a unique combination of contact-free experimental techniques toward investigating the effects of pressure on superconducting properties.

A slightly doped, non-superconducting sample of the insulating parent material Bi1.98Sr2.06Y0.68Cu2O8+δ shows anomalies in electronic Raman background, electron-phonon coupling λ, spectral weight transfer, density dependent behaviour of phonons and magnons, and c-axis compressibility with pressure at 21 GPa, which are directly related to the changes in physical properties observed in the material at the critical doping level. The results suggest that compression along the c-axis brings CuO2 layers closer together and leads to increased hole-doping to the optimal level, which would lead to the onset of superconductivity at the appropriate temperature.

The work has been published in the May 30, 2008 issue of Physical Review Letters, and opens up new avenues of fundamental research aimed at understanding the phenomenon of high-temperature superconductivity and its response to applied pressure. [Cuk et al., Phys. Rev. Lett., 100, 217003 (2008)]


APS Workshop Announcement PDF Print E-mail
A Workshop on Understanding Condensed Matter Dynamics at the Microscopic Level will be held at the Advanced Photon Source, Argonne National Laboratory on June 23-24, 2008. It is being organized by Yogi Gupta (WSU), Christian Mailhiot (DOE-NNSA), and Dennis Mills (APS).

The goal of the Workshop is to see how national facilities like the APS can be utilized to examine and understand the real time response of dynamically compressed materials at the microscopic level. It is a one and a half day workshop, consisting of invited talks and posters. Participants will be from universities, national laboratories, and research institutes in the U.S. and abroad. Limited travel support will be available for CDAC academic participants. For registration and more information, please go to: http://www.aps.anl.gov/News/Conferences/2008/DC_Workshop/

If you choose to present a poster, please send the title via email.

CDAC Welcomes Eight New Academic Partners PDF Print E-mail
CDAC is pleased to announce the addition of eight new academic partner groups. This addition brings to 19 the number of academic partners supporting graduate student research in high pressure materials science by CDAC.

Graduate students will be supported in groups led by: Robert Downs (University of Arizona), Steven Jacobsen (Northwestern University), Raymond Jeanloz (University of California-Berkeley), Abby Kavner (University of California-Los Angeles), Jie Li (University of Illinois), Wendy Mao (Stanford University), Wendy Panero (Ohio State University) and James Schilling (Washington University-St. Louis).

With the addition of our new academic partners, the total number of graduate students receiving support through CDAC for work toward the PhD degree will increase to 25 students per year.

Follow this link for more information on the work of CDAC academic partners.

 


Citroni, M., R. Bini, P. Foggi, and V. Schettino, Role of electronic states in the high-pressure amorphization of benzene, Proc. Nat. Acad. Sci., 105, 7658-7663 (2008).

Struzhkin, V. V., A. F. Goncharov, R. Caracas, H. K. Mao, and R. J. Hemley, Synchrotron infrared spectroscopy of the pressure-induced insulator-metal transitions in glassy As2S3 and As2Se3, Phys. Rev. B. 77, 165113 (2008).
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Welcome

CDAC is an interdisciplinary center headquartered at the Geophysical Laboratory of the Carnegie Institution of Washington. Our goals are to advance and perfect an extensive set of high P-T techniques and unique facilities, to perform key studies on a broad range of important materials in newly-accessible P-T regimes, and to integrate and coordinate static, dynamic and theoretical results for Stewardship Science applications.