An international team of scientists has reported the first experimental observation of the quantum critical point (QCP) in the extensively studied “unconventional superconductor” TiSe2, finding that it does not reside as predicted within the superconducting dome of the phase diagram, but rather at a full GPa higher in pressure.
The surprising result, reported in Nature Physics, suggests that the emergence of superconductivity in TiSe2 isn’t associated with the melting of a charge density wave (CDW), as prevailing theory holds; in fact the CDW’s amplitude decreases under increasing pressure, but does not disappear at zero resistance.
The researchers find that the emergence of superconductivity in this material is connected rather with the formation of domain walls between commensurate and incommensurate phase transitions. The discovery of this new phase boundary has implications for our understanding of superconducting behavior.
The experiments, conducted by Young Il Joe, a graduate student working with condensed matter physicist Peter Abbamonte, employed a novel X-ray scattering technique at the Cornell High Energy Synchrotron Source (CHESS) to obtain the first ever measurements of the degree of commensurability of the CDW order parameter.
In this, the researchers took advantage of the harmonics of the diffractive optics—usually filtered out in X-ray experiments—to take two readings simultaneously. The wavelengths of two simultaneous photon beams were carefully calibrated, one to measure the periodicity of the crystal lattice, the other to measure the periodicity of the electrons, and compare the two.
At low energies, the CDW was found to be commensurate, as expected, but above the superconducting dome, incommensurate behavior emerged as the temperature was increased. The superconducting characteristics of TiSe2 are typical of other unconventional superconducting materials that exhibit the universal phase diagram, suggesting a fundamental connection between unconventional superconductivity and the quantum dynamics of domain walls.
This work sheds new light on our understanding to the theorized connection between superconductivity and other ordered states, such as charge density wave (CDW), antiferromagnetism, or stripe order and could contribute to the eventual development of better superconducting materials, and ultimately to the possible invention of room-temperature superconductors.
The X-ray experiments were supported by the U.S. Department of Energy under Grant No. DE-FG02-06ER46285. Young Il Joe, Shi Yuan, and Lance Cooper grew the 1-TiSe2 crystals at the Frederick Seitz Materials Research Laboratory at the University of Illinois at Urbana-Champaign with support from DOE Grant No. DE-FG02-07ER46453. Use of the CHESS was supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF award DMR-0936384.
T.C. Chiang’s contributions were supported by DOE Grant No. DE-FG02-07ER46383. The conclusions presented are those of the scientists and not necessarily those of the funding agencies. Contact: Peter Abbamonte, Department of Physics, University of Illinois at Urbana-Champaign, 217/244-4861. Siv Schwink, communications coordinator, Department of Physics, University of Illinois at Urbana-Champaign, 217/300-2201.
Peter Abbamonte | EurekAlert!
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering