Physicists design material that conducts one way and insulates the other.
Stiffness and springiness could make heat stop and go.
European physicists have sketched out a blueprint for a valve that lets heat pass only one way. The proposed material conducts heat flowing in one direction, but also behaves as an insulator, stopping it going the other way1.
In theory, a heat valve could keep parts of microelectronic circuitry cool or channel heat to chip-sized chemical reactors, which are currently being developed for high-efficiency chemical synthesis or ultra-sensitive analysis.
Heat corresponds to the movement of atoms. When atoms are joined together in molecules, they vibrate back and forth. The larger the vibrations, the hotter the material.
Heat is conducted along a chain of particles because vibrations travel from one particle to the next. If one end is attached to a hot material and the other to something cooler, the hot end jiggles more. This jiggling goes down the chain to the cool end.
A chain of particles of identical weights linked by ideal, so-called harmonic springs vibrates at the same frequency irrespective of the amplitude of the vibrations. In real chains, like DNA, the links are not ideal, but anharmonic: their vibration frequency depends on amplitude.
One-way heat transfer would make use of anharmonicity. A chain divided into three sections, say Terraneos team, can insulate heat if the middle section acts like a strongly anharmonic spring while the outer two are softer and more harmonic.
If one of the end sections is stiffer than the other, more heat can flow in one direction than the other. The anharmonic middle of the chain can jiggle in sympathy with the stiff end when it is cold and the soft end when it is hot - but not vice versa. So the chain transmits heat from a hot, soft end to a cool stiff end. If the stiff end gets hot and the soft cold, the middle section blocks vibrations, so the chain as a whole acts as an insulator.
PHILIP BALL | © Nature News Service
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication
16.07.2018 | Chinese Academy of Sciences Headquarters
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 | Power and Electrical Engineering
17.07.2018 | Life Sciences
16.07.2018 | Physics and Astronomy