Polaron Coherence Condensation in Layered Colossal Resistive Manganites
Novel quantum phenomena, such as high-temperature superconductivity (HTSC) and colossal magnetoresistance (CMR), arise in certain materials where the interactions between electrons are very strong, but the mechanism driving their appearance remains a major puzzle. Now, angle-resolved photoemission findings from an international team led by researchers from Stanford University and the ALS provide the first direct spectroscopic evidence that the transition from insulator to metal in CMR manganese oxides (manganites) results from coherent “polaron condensation.” The new findings also suggest that coherence-driven transitions are a generic controlling factor for novel quantum phenomena in doped transition-metal oxides. Read more…
N. Mannella, W.L. Yang, K. Tanaka, X.J. Zhou, H. Zheng, J.F. Mitchell, J. Zaanen, T.P. Devereaux, N. Nagaosa, Z. Hussain, and Z.-X. Shen, “Nodal quasiparticle and polaron coherence condensation in layered colossal resistive manganites,” Phys. Rev. B 76, 233102 (2007).
Electric-Field Control of Local Ferromagnetism with a Magnetoelectric Multiferroic
Magnetoelectric multiferroics—materials that simultaneously show some form of magnetic and ferroelectric order—have excited condensed-matter researchers worldwide with the promise of coupling between magnetic and electric order parameters. A Berkeley–Stanford–Swiss group has now used the multiferroic bismuth–iron–oxygen compound BiFeO3 (BFO) to explore electrical control of magnetism through exchange coupling with a ferromagnet. Their experiments reveal the possibility of controlling ferromagnetism with an electric field at room temperature, a capability that could result in new and novel devices for magnetic data storage, spintronics, and high-frequency magnetic devices. Read more…
Publication about this research: Y.-H. Chu, L.W. Martin, M.B. Holcomb, M. Gajek, S.-J. Han, Q. He, N. Balke, C.-H. Yang, D. Lee, W. Hu, Q. Zhan, P.-L. Yang, A. Fraile-Rodríguez, A. Scholl, S.X. Wang, and R. Ramesh, “Electric-field control of local ferromagnetism using a magnetoelectric multiferroic,” Nature Mater. 7, 478 (2008).
The Completion of XM-2 Heralds a New Era in Biological Imaging at the ALS
Noted American physicist Richard Feynman once said “make the microscope one hundred times more powerful, and many problems in biology would be made very much easier.” Four years ago, Carolyn Larabell, Mark Le Gros, and the staff of the National Center for X-Ray Tomography (NCXT) at Beamline 2.1 took Feynman’s words to heart and began the construction of XM-2, a new transmission soft x-ray microscope. This was the first such imaging facility in the world to be designed specifically for biological imaging. Fast forward to the present and the original vision has been realized. XM-2 is now fully commissioned and producing an unprecedented number of high-resolution three-dimensional tomograms of cells in their native state. Each imaging experiment only takes three minutes or less. The large field of view on XM-2 equates to relatively large numbers of cells being imaged in each experiment. For bacteria and yeast, this can vary from a handful to upwards of 40 tomograms being produced per experiment. Consequently, XM-2 has been prodigiously productive in the short period since it was commissioned. With existing techniques, such as electron microscopy, obtaining data to reconstruct a tomogram of even a single yeast cell is considered a Herculean achievement. With XM-2 this has become a relatively trivial task.
All of this beautiful work is now showing up in the literature, the most recent of which was the cover article of the Journal of Structural Biology (Parkinson et al., J. Struc. Biol. 162, 380 ). This paper describes the unique characteristics of soft x-ray microscopy as a biological imaging tool. For the first time, the organelles inside a cell can be imaged quantitatively. This is essential for understanding the mechanisms that take place in normal cells and how they may change as a result of disease.
The next phase is the incorporation of other imaging tools into XM-2, the most notable of which is a high-aperture cryogenic light microscope (for which Larabell and Le Gros were recently awarded patent rights). This resultant multimodal imaging capability has created enormous excitement in the field. For the first time, it will be possible to image and identify fluorescently labeled molecules inside a cell then overlay this information onto a full soft x-ray 3D reconstruction. This revolutionary instrument and the developed correlated imaging methods ensure the ALS will remain at the forefront of biological and biomedical science for the foreseeable future and be a vital new tool for addressing the missions of NIH and DOE. For more information on becoming an NCXT user, click here.
French Students Spend Summer at ALS Beamlines
The ALS hosts students from high school to graduate school and from all over the world. One of our most successful collaborations is the ALS/ENSICAEN internship program, organized by ALS scientist Fred Schlachter and ENSICAEN professor Gilles Ban. ENSICAEN, located in Caen, France, offers engineering degrees in electronics, computer science, and material science and chemistry. “So many students were interested in coming to Berkeley that I had to find other hosts,” says Fred.
This summer, six students interned with scientists Wayne Stolte, Alex Aguilar, and Michael Martin. Maxime Taupin worked with Wayne Stolte (of the University of Nevada, Las Vegas) at Beamline 9.3.1 . Maxime used LabView to computerize and automate a magnetic mass spectrometer. As a part of his project, he consulted with engineers Mike Bell and Brian Smith to further understand the programming and electronics required for his project. Xavier Joubert and Claire Morichau Beauchant worked with Mike Martin on Beamline 1.4.3. Xavier is with ENSICAEN, Claire is with a similar program at the Ecole Nationale Supérieure de Physique in Grenoble. Xavier worked on two projects to use piezo-driven mirrors to scan the IR beam across the sample for faster mapping capabilities and determined how to make use of an array detector with actuated mirrors to drive the beam to different pixels within the array. Claire worked on a novel method to collect spectral images more rapidly using image compression techniques.
Mathilde Blanc, Mathieu Augustin, and Vincent Schoepff worked with Alex Aguilar and René Bilodeau at Beamline 10.0.1. Matilde created an IDL program incorporating data analysis routines previously written by René and which makes these tools more user friendly. Mathieu, using a flight electron/ion simulation program called SIMION, performed all simulations needed for a series of modifications to an existing velocity map imaging detector at Beamline 10. Vincent worked on a program that reads and facilitates analysis of undulator and grating calibration data from Beamline 10.0.1 and produces the look-up tables for beamline operation. All three students actively participated during a beamtime led by Alex, measuring photoelectron angular distributions for single and double ionization of He atoms at threshold energies.
The relationship between the scientists and the students is reciprocal. The interns get the hands-on training they need to further their scientific and engineering education and an understanding of the difference between a scientist, who spends more time gathering and analyzing data, and an engineer, who mainly designs and puts the pieces together. In turn, the scientists are rewarded with a fresh point of view to old problems, which can stimulate new solutions.
ALS Users’ Meeting Info Update
General information, meeting deadlines, and online registration for this year’s ALS Users’ Meeting, to be held at Berkeley Lab on October 13–15, 2008, are posted on the Users’ Meeting Web site.
This year, ten workshops will follow the end of the formal Users’ Meeting program, beginning Tuesday morning (October 14) and continuing through the morning of Wednesday, October 15. One will be held jointly with SSRL.
Workshop agendas will be posted as soon as speakers are confirmed. Information on how to register and how to contact workshop organizers is available on the Users’ Meeting Workshops Web page.
Abstract submissions for consideration for oral presentation: Friday, August 15
ALS users and staff are also asked to take a minute and nominate an ALS staff member or user whose extra effort deserves recognition for an ALS scientific or user support award (click here to nominate). The deadline for nominations is Friday, September 19.
ALS Doctoral Fellowship Application Deadline Extended to 7/31/08
These fellowships allow students who have passed their Ph.D. qualifying or comprehensive verbal and written exams (generally third-year students) to acquire hands-on scientific training and develop professional maturity for independent research. Applicants must be full-time, currently enrolled students in a Ph.D. program in the physical or biological sciences, pursuing thesis research based on the use of synchrotron radiation. Click here for more information and to apply.
New Directions in X-Ray Light Sources
ALS Director Roger Falcone is featured speaking on ultrafast x-ray pulses.on Berkeley Lab YouTube in the fourth in this year’s series of summer lectures. To view, click here.
Stanford–Berkeley Summer School on Synchrotron Radiation: August 17–22, 2008
The sixth Stanford–Berkeley summer school will provide basic lectures on the synchrotron radiation process, requisite technologies, and a broad range of scientific applications. The summer school will be housed on the Stanford University campus in Palo Alto. Co-chairs are Professors Anders Nilsson and David Attwood. Visits to both the Stanford Synchrotron Radiation Laboratory (SSRL) and the ALS will be included, with opportunities to interact with the professional staff and graduate students at both facilities. For more information and instructions on how to apply, click here.
For the user runs from June 17 to July 16: Beam reliability*: 87.1%; Completion**: 74.3%. Beam time was lost due to faults in multiple subsystem categories, including waterflow faults, interlock trips, power supply faults, and general AC power variations.
Questions about beam reliability should be sent to David Richardson.
Requests for special operations use of the “scrubbing” shift should be sent to Rick Bloemhard (ALS-CR@lbl.gov, x4738) by 1:00 p.m. Friday.