An important model to explain high-temperature superconductivity is the so-called ‘quantum spin liquid’. Scientists are therefore interested in understanding the low-energy excitations of this magnetic state.
Now, a theoretical study by a research team from RIKEN and the Massachusetts Institute of Technology, USA, has explained how the properties of spin liquids could be revealed by a simple heat-transfer experiment.
In an insulating magnetic crystal, the electronic spins are localized to the atoms that form the crystal lattice. For most such magnets, or antiferromagnets, the chemical bonds favor an arrangement where, at low temperatures, each spin points in a direction opposite to that of its neighbor. However, on a triangular lattice, such as the ‘Kagome lattice’, a spin cannot simultaneously be opposite to all of its neighbors. The spins in these magnets never order, even at very low temperatures—giving rise to the name quantum spin liquid.
“Spin liquids have an exotic electronic state because [their] electrons can effectively dissociate into distinguishable spin- and charge-carrying particles,” explains team-member Naoto Nagaosa from the RIKEN Advanced Science Institute, Wako. “The spin-carrying particle is called a spinon and determines the low-energy properties of the magnet.”
To date, however, few experiments have found spinons. Nagaosa and his collaborators explain how a method similar to the so-called ‘Hall measurement’—an indispensible technique for studying the properties of semiconductors—could be used to detect spinons.
In the classic version of the Hall measurement, a magnetic field is applied perpendicular to a charge-carrying current, causing positive charges to curve one way and negative charges the other. The deflection of the charges provides information about their properties, including their sign.
In the ‘thermal Hall effect’ considered by Nagaosa and his colleagues, temperature serves as the driving force to create a current—not of charges, but of magnetic excitations—that flow in a magnetic field. For a spin liquid, these excitations are the spinons. As in the classic Hall effect, a magnetic field will deflect these excitations, which will change the direction of the heat flow—an effect that experimentalists should be able to measure.
Nagaosa and his colleagues showed that while there is no thermal Hall effect in most conventional antiferromagnets, the presence of spinons in a spin liquid would result in a clear effect. This experimental probe could therefore become an important way to identify and study excitations of quantum magnets.
The corresponding author for this highlight is based at the Cross-Correlated Materials Research Group, RIKEN Advanced Science Institute
1. Katsura, H., Nagaosa, N. & Lee, P.A. Theory of the thermal Hall effect in quantum magnets. Physical Review Letters 104, 066403 (2010).
gro-pr | Research asia research news
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
New survey hints at exotic origin for the Cold Spot
26.04.2017 | Royal Astronomical Society
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Materials Sciences
26.04.2017 | Agricultural and Forestry Science
26.04.2017 | Physics and Astronomy