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Physics and Astronomy Cover: Close-Up Photo of Single Crystals of Geometrically Frustrated Antiferromagnets, Such As Strontium Holmium Oxide

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Physics and Astronomy Cover: Close-Up Photo of Single Crystals of Geometrically Frustrated Antiferromagnets, Such As Strontium Holmium Oxide Johns Hopkins University 2011 Physics and Astronomy Cover: Close-up photo of single crystals of geometrically frustrated antiferromagnets, such as strontium holmium oxide. The crystals pictured here were grown in the crystal-growth facility of the Department of Physics and Astronomy’s Institute for Quantum Matter by research scientist Seyed Koohpayeh. Conflicting magnetic interactions in these materials pro- duce a rich variety of emergent phenomena, including the exotic spin-liquid state of matter. This page: The crystals at approximately 2.5 times their actual size. See related article on page 6. TABLE OF CONTENTS Letter from the Chair 1 Chasing the Origins of the Universe 2 Discovery on a Grand Scale 4 A New Spin on Quantum Matter 6 Research Briefs 8 People 11 Physics and Astronomy is an annual publication of the Johns Hopkins University Zanvyl Krieger School of Arts and Sciences Department of Physics and Astronomy. Send correspondence to: Kate Pipkin, 3400 N. Charles Street, Wyman 500W, Baltimore, MD 21218 or [email protected]. Editor Kate Pipkin Managing Editor Ian Mathias Design Johns Hopkins Creative Services Photographer Will Kirk, Homewood Photography (unless otherwise noted) Letter from the Chair Dear alumni, colleagues, and friends, ctober 4 was a banner day for Johns Hopkins and especially for our Depart- ment of Physics and Astronomy. That was the day Adam Riess, who holds a OKrieger-Eisenhower Professorship in our department, was named a Nobel Prize winner for his leadership in the High-z Team’s 1998 co-discovery that the expansion rate of the universe is accelerating, a phenomenon widely attributed to an unexplained “dark energy” filling the universe. This level of achievement on the part of one of our faculty members is an affirmation of the intense quest for knowledge that is under way in our department every day. I believe that every physics and astronomy graduate has played some part in advancing the scholarship of this field. Each of you has a connection—be it past or present—to our department, and I know you share our pride in Adam’s great accomplishment. Even as we take time to celebrate this achievement (and celebrate we did!), the Department of Physics and Astronomy continues to move forward—sowing the seeds for the next round of discoveries in our disciplines. The department has recently embarked on a variety of new ventures, from a partnership with the National Laboratory of Solid State Microstructures at Nanjing University, to forefront work at the Large Hadron Collider at CERN, to building a state-of-the-art telescope in the Atacama Desert in Chile, and to numerous projects on the Homewood campus here in Baltimore. No matter where they work, our diverse faculty and students share a commitment to deepening our understanding of the most basic, irreducible foundations of nature. I am fortunate to keep the company of so many scholars dedicated to forging new frontiers for our discipline. In a similar vein, you hold in your hands another new venture for the department: an annual publication. Though it contains just a sampling of the work we have conducted over the past year, it will inform you of some of the department’s endeavors, and I hope it inspires you to remain in contact. Enjoy this inaugural issue. Best, Daniel Reich, Chair The Henry A. Rowland Department of Physics and Astronomy JOHNS HOPKINS UNIVERSITY PHYSICS AND ASTRONOMY 2011 1 PHA report_fin.indd 1 1/10/12 3:12 PM Chasing the Origins of the Universe… With a $5 million grant from the investigator for the 2001 Wilkinson Micro- Right down to the first trillionth National Science Foundation, Bennett is wave Anisotropy Probe space mission, which “One of the most leading a team developing a ground-based improved cosmic parameters by a factor of of a trillionth of a second telescope to study the origin of the universe. 30,000, fixing the age of the universe to rewarding things is strophysicist Charles “Chuck” The instrument will probe the cosmic within 1 percent accuracy.) ABennett has spent more than 25 years microwave background radiation—faint The instrument will work somewhat studying faint afterglow radiation from the traces of the universe’s very beginning, 13.7 like a satellite television dish. A reflector and seeing undergraduate earliest moments of the universe. billion years ago. circuitry within the instrument will intercept Bennett, the Alumni Centennial Called the Cosmology Large-Angular microwaves coming from space and direct and graduate students Professor of Physics and Astronomy who BY KAREN BLUM Scale Surveyor (CLASS), the telescope will the signal onto an array of tiny devices came to Johns Hopkins in 2005 from the search large regions of the sky for a specific (superconducting transition edge sensors or National Aeronautics and Space Administra- polarization pattern generated by gravita- bolometers), where that energy will be really dig into the tion (NASA), says there are many unan- tional waves formed during the first absorbed. The device heats up slightly due to swered questions about the universe. His is, moments of the universe. Bennett hopes it this absorbed energy, allowing the team to project. It’s a great “What happened at the very beginning?” will help provide a definitive test of the record the energy coming from different “You might think that this is not theory of inflation, which suggests that tiny directions of the sky. For this to be possible, answerable by humans,” he says, “and it may quantum mechanical energy fluctuations the team has to cool the detectors within the combination of not be, but we’re going to try.” suddenly grew at an enormous rate to an instrument to a tenth of a degree above astronomical size to start the universe. absolute zero. A position-cycled grid of wires enthusiasm and “This inflation theory, in my mind, is located in front of the instrument will rapidly like a theory that adds on to the beginning modulate the polarization state input to the of the Big Bang theory,” he says. “Inflation detectors so the instrument’s effects can be transfer of expertise.” theory actually is the theory of how things separated from sky polarization. got started.” While most cosmologists agree CLASS will be built at Johns Hopkins —M TOBIAS ARRIAGE, that the universe started very hot and dense and transported to the Atacama Desert of Assistant ProFESSOR and has been expanding and cooling ever northern Chile—one of the highest, driest since, the Big Bang theory many use to places on earth. Bennett has been working explain the universe’s origin has become with the Chilean government for permission misconstrued, Bennett says. According to to situate the instrument 17,000 feet above Princeton he worked on the Atacama him, the Big Bang theory clarifies how the sea level in an evolving astronomical park Cosmology Telescope (ACT), located on the universe has evolved, but it doesn’t tell us scattered with other telescopes and observa- same Chilean plateau where CLASS will how it began. tories. Last year, he visited the area to select a reside. Marriage studies clusters of galaxies Looking at the cosmic microwave specific location for the telescope, in view of that were found by their effect on the cosmic background is looking straight into the past, the town of San Pedro de Atacama, some microwave background, and uses this due to the finite speed of light, Bennett 9,000 feet below. Because the desert’s information to deduce additional properties explains. “We are directly looking at what the extreme temperatures and little oxygen make of the universe. universe looked like 13.7 billion years ago. It for an inhospitable work environment, he Marriage has been working closely isn’t an idea, or a concept, we are looking at plans to have an antenna transmit the data with Johns Hopkins physics and astronomy the light from 13.7 billion years ago, and from the telescope to town so team members students designing state-of-the-art technol- that’s what’s so cool about it…it’s incredibly can access the information on computers at a ogy for CLASS, including the optical exciting to try to use this data to figure out more moderate altitude, limiting the amount instrumentation and a shield to protect the what happened in the first trillionth of a of time spent on-site each day. detectors from the Earth’s magnetic field. trillionth of a second of the universe.” (It’s Now a year into the five-year grant, the “One of the most rewarding things is worth noting that Bennett was the principal team is well on its way to constructing the seeing undergraduate and graduate students telescope. A lab (pictured left) across from really dig into the project,” Marriage says. Bennett’s office houses part of the instru- “It’s a great combination of enthusiasm and Facing page: Several members of the CLASS team. ment’s core circuitry, as well as cryogenic transfer of expertise. From left: Assistant Professor Tobias Marriage, cooling equipment. An adjacent room holds “This is a real watershed moment,” Graduate Research Assistant Joseph Eimer, their polarization filter, consisting of hun- he adds. “This project hopefully will be the Professor Charles Bennett, and Undergraduate dreds of thin gold wires, stretched taut. gateway to many, many more cosmological Research Assistant Tiffany Wei. Between Eimer A key member of the team is Assistant experiments over the next decades.” If and Bennett rests a helium refrigerator system Professor Tobias Marriage, who came to CLASS detects the anticipated signal, it and dewar, which are used in conjunction to cool Johns Hopkins last year from Princeton would be the first-ever detection of the CLASS detectors to 100 millikelvin—just one-tenth University.
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