Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

“Bethe Strings” experimentally demonstrated as many-body quantum states for the first time

12.02.2018

The synthesis of quasi one-dimensional magnets and their investigation by means of optical spectroscopy in extremely high magnetic fields led to success

“Bethe strings” are excitations of strongly bound electron spins in one-dimensional quantum spin systems. These quantum spin states are named after the physicist Hans Bethe, who first described them theoretically in 1931. “Bethe Strings” have now been proved for the first time experimentally by the Augsburg physicists Prof. Dr. Alois Loidl and Dr. Zhe Wang, who are reporting on it in the internationally renowned journal "Nature" (issue of 8 February 2018) together with their cooperation partners from Berlin, Dresden, Mumbai, Nijmegen and San Diego.


In SrCo₂V₂O₈ the cobalt ions (CO²⁺) form in the interior of a chain of edges-linked oxygen octahedra a quasi-one-dimensional electron spin chain with spin S = ½.

© Universität Augsburg/IfP/EP V


The state of a ferromagnetic chain of spins of the cobalt ions in SrCo₂V₂O₈ (a) compared to a spin chain with coupled two- or three-string excitations (b or c).

© Universität Augsburg/IfP/EP V

In 1933 Hans Bethe fled to the USA from the Nazis and he contributed to the development of the atomic bomb as head of the theory department in Los Alamos. He was considered one of the leading nuclear physicists at the time.

He received the Nobel Prize for Physics in 1967 for the theory of energy production in stars. However, in his early scientific career, Bethe focused on solid-state physics, especially the electron theory of metals.

In 1931 he published a manuscript entitled “Eigenwerte und Eigenfunktionen der linearen Atomkette” in the “Zeitschrift für Physik” on quantum spin states in one dimension. He succeeded in finding an exact solution to the one-dimensional quantum mechanical many-body system based on a theory by Werner Heisenberg and with the so-called Bethe ansatz, a method that was later further developed theoretically and today is an important mathematical tool of statistical physics.

In this kind of system there is a one-dimensional chain of atoms at fixed positions that carry an electron spin S = ½. Many-body “string” states correspond to excitations of coupled quantum-mechanical spins, that is, magnetic self-rotation moments of the electrons that are tightly bound together and can move almost freely in the one-dimensional chain.

The lack of suitable one-dimensional materials and appropriate experimental methods has made experimental verification of this kind of many-particle “string” states and proving their excitations so far impossible. Extreme progress in material synthesis on one hand and the development of optical spectroscopy in the terahertz frequency range in very high magnetic fields on the other hand have now made this experimental detection possible for the first time.

In a first step, SrCo₂V₂O₈ crystals were synthesised and characterised at the Helmholtz-Zentrum in Berlin and at the High Magnetic Field Laboratory in the Helmholtz-Zentrum Dresden-Rossendorf. These crystals, in which the cobalt ions form a one-dimensional spin chain with spin = ½, were then used by Loidl and Wang in the High Field Magnet Laboratory of Radboud University in Nijmegen in a wide magnetic field range from 4 to 28 Tesla (for comparison: the Earth’s magnetic field in Central Europe has tested a strength of about 0.00005 Tesla). The discovered “string” excitations were finally calculated by scientists from the University of California at San Diego with the Bethe ansatz and described exactly.

“The evidence we have provided of the existence and stability of these exotic spin structures and excitations is a tremendous step forward, initially in terms of further research into spin dynamics in the field of quantum magnetism”, explains Loidl. However, this also applies to many other areas for which the application and further development of the Bethe ansatz are of outstanding importance – ranging from cold quantum gases and string theory in elementary particle physics to problems in quantum information systems.

Publication:

Zhe Wang, Jianda Wu, Wang Yang, Anup Kumar Bera, Dmytro Kamenskyi, A.T.M. Nazmul Islam, Shenglong Xu, Joseph Matthew Law, Bella Lake, Congjun Wu, Alois Loidl: Experimental Observation of Bethe Strings, Nature 554, 219–223 (08 February 2018); DOI: 10.1038/nature25466; http://www.nature.com/articles/nature25466

Contact person at the University of Augsburg:

Prof. Dr. Alois Loidl
Chair for Experimental Physics V/Electronic Correlations and Magnetism
Telephone +49(0)821/598-3600
Alois.loidl@physik.uni-augsburg.de

Dr. Zhe Wang
Currently Helmholtz-Zentrum Dresden-Rossendorf
Telephone +49(0)351/260-2691
zhe.wang@hzdr.de

Weitere Informationen:

http://www.nature.com/articles/nature25466

Klaus P. Prem | idw - Informationsdienst Wissenschaft

More articles from Physics and Astronomy:

nachricht Astronomers see 'warm' glow of Uranus's rings
21.06.2019 | University of California - Berkeley

nachricht A new force for optical tweezers awakens
19.06.2019 | University of Gothenburg

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fraunhofer IDMT demonstrates its method for acoustic quality inspection at »Sensor+Test 2019« in Nürnberg

From June 25th to 27th 2019, the Fraunhofer Institute for Digital Media Technology IDMT in Ilmenau (Germany) will be presenting a new solution for acoustic quality inspection allowing contact-free, non-destructive testing of manufactured parts and components. The method which has reached Technology Readiness Level 6 already, is currently being successfully tested in practical use together with a number of industrial partners.

Reducing machine downtime, manufacturing defects, and excessive scrap

Im Focus: Successfully Tested in Praxis: Bidirectional Sensor Technology Optimizes Laser Material Deposition

The quality of additively manufactured components depends not only on the manufacturing process, but also on the inline process control. The process control ensures a reliable coating process because it detects deviations from the target geometry immediately. At LASER World of PHOTONICS 2019, the Fraunhofer Institute for Laser Technology ILT will be demonstrating how well bi-directional sensor technology can already be used for Laser Material Deposition (LMD) in combination with commercial optics at booth A2.431.

Fraunhofer ILT has been developing optical sensor technology specifically for production measurement technology for around 10 years. In particular, its »bd-1«...

Im Focus: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on UV LED Technologies & Applications – ICULTA 2020 | Call for Abstracts

24.06.2019 | Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

 
Latest News

Cooling with the sun

25.06.2019 | Power and Electrical Engineering

Robocabs: The mobility of the future?

25.06.2019 | Studies and Analyses

Skipping Meat on Occasion May Protect Against Type 2 Diabetes

25.06.2019 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>