A team led by the Department of Energy's Oak Ridge National Laboratory has used sophisticated neutron scattering techniques to detect an elusive quantum state known as the Higgs amplitude mode in a two-dimensional material.
The Higgs amplitude mode is a condensed matter cousin of the Higgs boson, the storied quantum particle theorized in the 1960s and proven experimentally in 2012. It is one of a number of quirky, collective modes of matter found in materials at the quantum level. By studying these modes, condensed matter researchers have recently uncovered new quantum states known as quasiparticles, including the Higgs mode.
The ORNL-led research team selected a crystal composed of copper bromide -- because the copper ion is ideal for studying exotic quantum effects -- to observe the elusive Higgs amplitude mode in two dimensions. The sample was examined using cold neutron triple-axis spectrometer beams for neutron scattering at the High Flux Isotope Reactor.
Credit: Genevieve Martin, Oak Ridge National Laboratory/Dept. of Energy
These studies provide unique opportunities to explore quantum physics and apply its exotic effects in advanced technologies such as spin-based electronics, or spintronics, and quantum computing.
"To excite a material's quantum quasiparticles in a way that allows us to observe the Higgs amplitude mode is quite challenging," said Tao Hong, an instrument scientist with ORNL's Quantum Condensed Matter Division.
Although the Higgs amplitude mode has been observed in various systems, "the Higgs mode would often become unstable and decay, shortening the opportunity to characterize it before losing sight of it," Hong said.
The ORNL-led team offered an alternative method. The researchers selected a crystal composed of copper bromide, because the copper ion is ideal for studying exotic quantum effects, Hong explained. They began the delicate task of "freezing" the material's agitating quantum-level particles by lowering its temperature to 1.4 Kelvin, which is about minus 457.15 degrees Fahrenheit.
The researchers fine-tuned the experiment until the particles reached the phase located near the desired quantum critical point--the sweet spot where collective quantum effects spread across wide distances in the material, which creates the best conditions to observe a Higgs amplitude mode without decay.
With neutron scattering performed at ORNL's High Flux Isotope Reactor, the research team observed the Higgs mode with an infinite lifetime: no decay.
"There's an ongoing debate in physics about the stability of these very delicate Higgs modes," said Alan Tennant, chief scientist of ORNL's Neutron Sciences Directorate. "This experiment is really hard to do, especially in a two-dimensional system. And, yet, here's a clear observation, and it's stabilized."
The research team's observation provides new insights into the fundamental theories underlying exotic materials including superconductors, charge-density wave systems, ultracold bosonic systems and antiferromagnets.
"These breakthroughs are having widespread impact on our understanding of materials' behavior at the atomic scale," Hong added.
The study, titled, "Direct observation of the Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point," was published in Nature Physics. It was co-authored by ORNL's Tao Hong, Sachith E. Dissanayake, Harish Agrawal and David A. (Alan) Tennant, and scientists from Shizuoka University, the National Institute of Standards and Technology, University of Maryland, University of Jordan, Clark University, Helmholtz-Zentrum Berlin for Materials and Energy and Lehrstuhl für Theoretische Physik I.
The team used cold neutron triple-axis spectrometer beams for studying exotic magnetic effects and analyzed low-energy excitations in the copper bromide compound. The unpolarized neutron scattering measurements were performed at ORNL's HFIR and at Helmholtz-Zentrum Berlin for Materials and Energy. For contrasting data from polarized neutron-scattering measurements, they also employed a high-intensity multi-axis crystal spectrometer at NIST's Center for Neutron Research.
The work performed at ORNL's HFIR, a DOE Office of Science User Facility, and was funded by the DOE Office of Science.
UT-Battelle manages ORNL for DOE's Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.
Sara Shoemaker | EurekAlert!
Gamma-ray flashes from plasma filaments
18.04.2018 | Max-Planck-Institut für Kernphysik
How does a molecule vibrate when you “touch” it?
17.04.2018 | Universität Regensburg
Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.
The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...
Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.
Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...
In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...
In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.
Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...
The Atlantic overturning – one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards – is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century, according to a study published in the highly renowned journal Nature by an international team of scientists. Human-made climate change is a prime suspect for these worrying observations.
“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the...
13.04.2018 | Event News
12.04.2018 | Event News
09.04.2018 | Event News
19.04.2018 | Power and Electrical Engineering
19.04.2018 | Life Sciences
18.04.2018 | Materials Sciences