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 New type of low-energy nanolaser that shines in all directions
18.12.2018 | Eindhoven University of Technology

nachricht NASA research reveals Saturn is losing its rings at 'worst-case-scenario' rate
18.12.2018 | NASA/Goddard Space Flight Center

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: Data storage using individual molecules

Researchers from the University of Basel have reported a new method that allows the physical state of just a few atoms or molecules within a network to be controlled. It is based on the spontaneous self-organization of molecules into extensive networks with pores about one nanometer in size. In the journal ‘small’, the physicists reported on their investigations, which could be of particular importance for the development of new storage devices.

Around the world, researchers are attempting to shrink data storage devices to achieve as large a storage capacity in as small a space as possible. In almost...

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

NASA research reveals Saturn is losing its rings at 'worst-case-scenario' rate

18.12.2018 | Physics and Astronomy

Researchers observe charge-stripe crystal phase in an insulating cuprate

18.12.2018 | Materials Sciences

Switch-in-a-cell electrifies life

18.12.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>