Quasiparticle Behavior in Bose Quantum Liquids

Quasiparticle Behavior in Bose Quantum Liquids March 25, 2005

LOS ANGELES, CA - Quasiparticles carry energy in condensed matter. In the world of quasiparticle physics, understanding when and how these energy carriers fail opens doors to another level of understanding, and can lead the way to many new and important theories. Scientists at the U. S. Department of Energy’s Brookhaven National Laboratory have discovered the failure point for the quasiparticle construct, the standard model of condensed matter physics. This could have far-reaching implications, for example, in the study of high-temperature superconductors, materials currently under intense scrutiny as a possible replacement for the conventional superconducting materials now used in many facets of everyday life.

Physicist Igor Zaliznyak (click to view hi-res photo).

At the March 2005 meeting of the American Physical Society, Brookhaven physicist Igor Zaliznyak will explain how he and his colleagues identified the “spectrum endpoint” in a Bose quantum spin liquid, the point at which the quasiparticles are no longer well-defined energy carriers. Zaliznyak will discuss his paper at 1:39 p.m. Friday, March 25, 2005, in Room 515B of the Los Angeles Convention Center.

“Although the quantum-liquid state has been studied for roughly a century, it continues to fascinate physicists,” Zaliznyak said. “We have demonstrated that at higher energies, the Bose quasiparticle description fails because of quasiparticle decay.”

The study of quasiparticles, which govern the properties of quantum liquids, was pioneered by Russian Nobel Prize winning-physicist L.D. Landau. There are two types of quasiparticles, Bose and Fermi, and physicists around the globe are exploring the properties of each type. The Brookhaven experiments, conducted using the triple-axis neutron spectrometer at the National Institutes of Standards and Technology, confirmed that in a particular Bose quantum spin liquid, quasiparticle decay leads to spectrum termination, as was predicted by Landau.

“Landau proposed that at some energy, the quasiparticle description breaks down, and in a generic form this has been known,” Zaliznyak said. “But the extent of the phenomenon and how it reveals itself in real materials hasn’t been clear. We have shown that at twice the minimum excitation energy, known as the spin gap, Bose quasiparticles cease to be defined at all and disappear.”

The Brookhaven experiments studied a quantum liquid found in systems composed of quantum spins in magnetic crystals, specifically an organo-metallic material known as PHCC. The scientists’ neutron scattering measurements demonstrate the occurrence of spectrum termination in the two-dimensional quantum spin liquid found in PHCC.

“When you attempt to create an excitation that is more than twice the gap rate, it’s possible that your excitation decays, “ Zaliznyak said. “In Bose quantum liquids, when decay processes like this become allowed, you can’t have quasiparticles.”

The research was funded by the Office of Basic Energy Sciences within the U.S. Department of Energy's Office of Science, the National Science Foundation, and the Robert A. Welch Foundation.

Note to local editors: Igor Zaliznyak lives in Port Jefferson, New York.

Contact: Kay Cordtz, (631) 344-2710 or Mona S. Rowe, (631) 344-5056 SOURCE: Brookhaven National Laboratory

Forrest. Trembley Vietnam MIA

Missing In Action Serviceman Identified, The Department of Defense POW/Missing Personnel Office (DPMO) announced today that the remains of a U.S. Navy pilot, missing in action from the Vietnam War, have been identified and will be returned to his family for burial with full military honors.

Navy Lieutenant Commander J. Forrest G. Trembley of Spokane, Wash., will be buried in Arlington National Cemetery on April 1.

On August 21, 1967, Trembley and his fellow crewman took off in their A-6A Intruder from the U.S.S. Constellation on a strike mission against the Duc Noi rail yards near Hanoi, North Vietnam. On leaving the target area, their aircraft and another one in the flight were attacked by enemy MiGs. When last seen, the two aircraft were disappearing into the clouds near the Vietnamese-Chinese border. The last radio message from Trembley indicated the MiGs were in hot pursuit, but no further communications were heard.

Later that day, the Chinese government reported that two U.S. A-6s had been shot down over the People’s Republic of China (PRC). The broadcast noted that one of the four crewmen had been captured but the other three died in the shoot down. The Chinese released the surviving crewman in March 1973.

With the assistance of the Chinese government, a joint U.S.-PRC team interviewed witnesses to the shoot down and crash in 1993 and 1999. U.S. specialists from the Joint POW/MIA Accounting Command (JPAC) interviewed a Chinese citizen near the crash site. He turned over Trembley’s identification tag and fragmentary human remains alleged to be those of American pilots. The team recovered some pilot’s gear from a burial site, but found no additional human remains.

Scientists of the JPAC and the Armed Forces DNA Identification Laboratory used mitochondrial DNA as one of the forensic tools to identify the remains as those of Trembley.

Of the 88,000 Americans missing in action from all conflicts, 1,836 are from the Vietnam War, with 1,399 of those within the country of Vietnam. Another 747 Americans have been accounted for since the end of the Vietnam War.

For additional information on the Defense Department’s mission to account for missing Americans, visit the DPMO web site at www.dtic.mil/dpmo, or call 703-699-1169.

U.S. Department of DefenseOffice of the Assistant Secretary of Defense (Public Affairs)News Release On the Web: defenselink.mil/releases/ Media contact: +1 (703) 697-5131 Public contact: dod.mil/faq/comment or +1 (703) 428-0711 No. 289-05 IMMEDIATE RELEASE March 25, 2005