Matter shows abrupt escape from flatness: Lead made to undergo a rapid transition from 'pancake' to hemisphere

ScienceDaily (Sep. 28, 2011) — At first glance, it seems as if billions of lead atoms have mysteriously disappeared. When exposed to heat, a layer of lead coated onto a nickel surface becomes almost invisible from one moment to the next. In reality, the slightest disturbance causes these atoms to suddenly switch from a broad “flat pancake” shape to a compact hemisphere.

This remarkable phenomenon was first revealed by researchers at the University of Twente’s MESA+ Institute for Nanotechnology, who have since published their results in Physical Review Letters.

A lead coating on a nickel surface has unusual electronic properties which cause it to form flat "pancakes," consisting of billions of atoms arranged in a crystalline structure. These "pancakes" of solid lead are quantum mechanically stabilized and just a couple of dozen atoms thick. When exposed to gradual heating, nothing much changes at first. At about 520 Kelvin (247 degrees Celsius), however, the lead coating suddenly seems to disappear completely. Within the space of a few milliseconds, the lead "slivers" transform into hemispheres with a radius (or "height") of a few micrometers. Interestingly, this all takes place at a temperature below the melting point of lead. The hemispheres, too, consist of solid lead. So no mass has been lost, the material has simply taken on a different spatial configuration.

Low energy electron microscope

The technique used by the researchers to observe this process is known as Low Energy Electron Microscopy (LEEM). There are only a few such microscopes in existence, but two have recently been installed in the Netherlands. They are designed to bombard surfaces with low energy electrons. This makes them especially well suited to making accurate observations of surface phenomena and events in thin films.

Beyond the scope of our current knowledge

The abrupt transformation from flat to spherical can be explained in terms of the most energetically favourable shape. From this viewpoint, hemispheres make much more effective use of surfaces, whereas pancakes are not very stable. There has recently been a massive expansion in our understanding of atomic processes right down to the level of single atoms, facilitated by experimental techniques such as Scanning Tunnelling Microscopy (STM), together with newly developed theories. Even so, we cannot account for the sheer speed at which this transition takes place.

Group process

However, this recently discovered super-fast transition from two to three dimensions is based on a delicate interplay between several atoms, a kind of group process. In their published article, these researchers from Twente express the view that a more detailed explanation of the very rapid transition from flat to spherical will only be possible when we have a better fundamental theoretical understanding of meso-level phenomena. LEEM can be used to make direct observations of new phenomena at the meso-scale, thereby generating data crucial to our knowledge of this field. The importance of these results is that they will give us a more profound understanding of the stability of nanostructures.

This study was carried out by Prof. Harold Zandvliet's Physics of Interfaces and Nanomaterials group. Funding was provided by the FOM Institute. The group is part of the University of Twente's MESA+ Institute for Nanotechnology. The LEEM equipment used in this study was purchased with funds provided by the Dutch Technology Foundation (STW).

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Twente.

Journal Reference:

Tjeerd Bollmann, Raoul van Gastel, Harold Zandvliet, Bene Poelsema. Anomalous Decay of Electronically Stabilized Lead Mesas on Ni(111). Physical Review Letters, 2011; 107 (13) DOI: 10.1103/PhysRevLett.107.136103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Matter shows abrupt escape from flatness: Lead made to undergo a rapid transition from 'pancake' to hemisphere

ScienceDaily (Sep. 28, 2011) — At first glance, it seems as if billions of lead atoms have mysteriously disappeared. When exposed to heat, a layer of lead coated onto a nickel surface becomes almost invisible from one moment to the next. In reality, the slightest disturbance causes these atoms to suddenly switch from a broad “flat pancake” shape to a compact hemisphere.

This remarkable phenomenon was first revealed by researchers at the University of Twente’s MESA+ Institute for Nanotechnology, who have since published their results in Physical Review Letters.

A lead coating on a nickel surface has unusual electronic properties which cause it to form flat "pancakes," consisting of billions of atoms arranged in a crystalline structure. These "pancakes" of solid lead are quantum mechanically stabilized and just a couple of dozen atoms thick. When exposed to gradual heating, nothing much changes at first. At about 520 Kelvin (247 degrees Celsius), however, the lead coating suddenly seems to disappear completely. Within the space of a few milliseconds, the lead "slivers" transform into hemispheres with a radius (or "height") of a few micrometers. Interestingly, this all takes place at a temperature below the melting point of lead. The hemispheres, too, consist of solid lead. So no mass has been lost, the material has simply taken on a different spatial configuration.

Low energy electron microscope

The technique used by the researchers to observe this process is known as Low Energy Electron Microscopy (LEEM). There are only a few such microscopes in existence, but two have recently been installed in the Netherlands. They are designed to bombard surfaces with low energy electrons. This makes them especially well suited to making accurate observations of surface phenomena and events in thin films.

Beyond the scope of our current knowledge

The abrupt transformation from flat to spherical can be explained in terms of the most energetically favourable shape. From this viewpoint, hemispheres make much more effective use of surfaces, whereas pancakes are not very stable. There has recently been a massive expansion in our understanding of atomic processes right down to the level of single atoms, facilitated by experimental techniques such as Scanning Tunnelling Microscopy (STM), together with newly developed theories. Even so, we cannot account for the sheer speed at which this transition takes place.

Group process

However, this recently discovered super-fast transition from two to three dimensions is based on a delicate interplay between several atoms, a kind of group process. In their published article, these researchers from Twente express the view that a more detailed explanation of the very rapid transition from flat to spherical will only be possible when we have a better fundamental theoretical understanding of meso-level phenomena. LEEM can be used to make direct observations of new phenomena at the meso-scale, thereby generating data crucial to our knowledge of this field. The importance of these results is that they will give us a more profound understanding of the stability of nanostructures.

This study was carried out by Prof. Harold Zandvliet's Physics of Interfaces and Nanomaterials group. Funding was provided by the FOM Institute. The group is part of the University of Twente's MESA+ Institute for Nanotechnology. The LEEM equipment used in this study was purchased with funds provided by the Dutch Technology Foundation (STW).

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Twente.

Journal Reference:

Tjeerd Bollmann, Raoul van Gastel, Harold Zandvliet, Bene Poelsema. Anomalous Decay of Electronically Stabilized Lead Mesas on Ni(111). Physical Review Letters, 2011; 107 (13) DOI: 10.1103/PhysRevLett.107.136103

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Escaping gravity's clutches: Information could escape from black holes after all, study suggests

ScienceDaily (Aug. 11, 2011) — New research by scientists at the University of York gives a fresh perspective on the physics of black holes. Black holes are objects in space that are so massive and compact they were described by Einstein as "bending" space. Conventional thinking asserts that black holes swallow everything that gets too close and that nothing can escape, but the study by Prof. Samuel Braunstein and Dr. Manas Patra suggests that information could escape from black holes after all.

The implications could be revolutionary, suggesting that gravity may not be a fundamental force of nature.

Prof. Braunstein says: "Our results didn't need the details of a black hole's curved space geometry. That lends support to recent proposals that space, time and even gravity itself may be emergent properties within a deeper theory. Our work subtly changes those proposals, by identifying quantum information theory as the likely candidate for the source of an emergent theory of gravity."

But quantum mechanics is the theory of light and atoms, and many physicists are skeptical that it could be used to explain the slow evaporation of black holes without incorporating the effects of gravity.

The research, which appears in the latest issue of Physical Review Letters, uses the basic tenets of quantum mechanics to give a new description of information leaking from a black hole.

Prof. Braunstein says: "Our results actually extend the predictions made by well-established techniques that rely on a detailed knowledge of space time and black hole geometry."

Dr. Patra adds: "We cannot claim to have proven that escape from a black hole is truly possible, but that is the most straight-forward interpretation of our results. Indeed, our results suggest that quantum information theory will play a key role in a future theory combining quantum mechanics and gravity."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of York.

Journal Reference:

Samuel Braunstein, Manas Patra. Black Hole Evaporation Rates without Spacetime. Physical Review Letters, 2011; 107 (7) DOI: 10.1103/PhysRevLett.107.071302

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here