Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Two-dimensional melting of hard spheres experimentally unravelled after 60 years

24.04.2017

First definitive experimental evidence of two-dimensional melting of hard spheres

After extensive research, scientists from the Department of Chemistry at the University of Oxford have found experimental evidence that sheds new light on the melting of two-dimensional substances. Findings from the study could be used to support technological improvements to thin film materials such as graphene.


This is the interface between the liquid (top) and hexatic (bottom) states.

Credit: Oxford University

Researchers from the group of Professor Roel Dullens at Oxford's Department of Chemistry have experimentally elucidated how melting of a two-dimensional solid of hard spheres occurs. With this work they resolve one of the most fundamentally important but still outstanding issues in condensed matter science. In addition, these results provide the cornerstone for the further understanding and development of two-dimensional materials.

Melting, the phase transition in which a substance turns from a solid to a liquid, is widely understood in basic terms. But despite being encountered regularly in everyday life, (whether in the workplace, home or natural world), scientists have long been trying to understand the melting process on a fundamental level.

The melting of a solid into a liquid is one of the most commonly experienced scientific phenomena. However, understanding this transformation is especially mysterious for solids in two-dimensions. Here, the celebrated Kosterlitz-Thouless-Halperin-Nelson-Young (KTHNY) theory proposes that an intermediate, partially disordered state, called the 'hexatic', exists between the solid and liquid.

Substantial effort has been made towards the understanding of these 'topological' transitions, for which Kosterlitz and Thouless were awarded the 2016 Nobel Prize in Physics [1,2]. Yet for the simplest interacting system of many particles, two-dimensional hard spheres, there has been an astonishing lack of consensus despite the first simulations being performed over 60 years ago.

Dr Alice Thorneywork and co-workers used optical microscopy to study monolayers of colloidal model hard spheres (see box 2) tilted by a small angle to introduce a gradient in the particle concentration [FIG 1]. For hard spheres, the behaviour is governed only by this concentration, which allowed them to identify and characterize the liquid, hexatic, and solid states and the nature of the transitions between them in a single experiment. The results show that the melting occurs via a continuous solid-hexatic transition followed by a first order hexatic-liquid transition [FIG 2].

###

[1] http://www.prospectmagazine.co.uk/blogs/philip-ball/who-has-won-the-physics-nobel-and-why

[2] https://www.forbes.com/sites/chadorzel/2016/10/08/how-this-years-nobel-laureates-in-physics-changed-the-game/#42916adf168f

Image info:

BOX 1: Two-dimensional hard spheres (similar make-up to a snooker ball triangle)

Hard spheres are simply solid balls that cannot overlap. When these spheres are confined to monolayer, just like the balls on a snooker table, this corresponds to a system of two-dimensional hard spheres. A collection of hard spheres is the simplest possible system that exhibits melting from a solid into a liquid.

BOX 2: Colloidal particles:

Colloidal particles have a typical size between a nanometre (a millionth of millimetre) and a micrometre (a thousandth of a millimetre). Spherical colloidal particles suspended in a liquid such as water are the best experimental realisation of micrometre-sized hard spheres (the scale bar in the image below corresponds to 1 micro-metre).

Fig 1:A microscopy image of the two-dimensional colloidal hard sphere system titled by a small angle ?.

Fig 2:The interface between the liquid (top) and hexatic (bottom) states.

The full study citation is as follows:

Two-Dimensional Melting of Colloidal Hard Spheres
Alice L. Thorneywork, Joshua L. Abbott, Dirk G.?A.?L. Aarts, and Roel P.?A. Dullens
Phys. Rev. Lett. 118, 158001 - Published 10 April 2017

For further information please contact Lanisha Butterfield in the University of Oxford press office at Lanisha.butterfield@admin.ox.ac.uk or on+44 (0)1865 280531

The Mathematical, Physical and Life Sciences Division (MPLS) is one of four academic divisions at the University of Oxford, representing the non-medical sciences. Oxford is one of the world's leading universities for science, and MPLS is at the forefront of scientific research across a wide range of disciplines. Research in the mathematical, physical and life sciences at Oxford was rated the best in the UK in the 2014 Research Excellence Framework (REF) assessment. MPLS received £133m in research income in 2014/15.

Media Contact

Lanisha Butterfield
lanisha.butterfield@admin.ox.ac.uk
01-865-280-531

 @UniofOxford

http://www.ox.ac.uk/ 

Lanisha Butterfield | EurekAlert!
Further information:
https://eurekalert.org/pub_releases/2017-04/uoo-tmo042117.php

More articles from Life Sciences:

nachricht At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History

nachricht New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>