Physicists have identified a key property of insulating and conductive material




Triple point

Scientists are well-known three main states of water – solid, liquid and gaseous. The coexistence of the three phases is possible only under strictly defined temperature and pressure. Such sustainable equilibrium is called the triple point.

It is also known that many materials are solid form can exist in various phases, but to determine the pressure and temperature in the existence of an equilibrium point of the three phases is very difficult.

For the first time, scientists have determined the exact coordinates of the triple point of a substance called vanadium dioxide (VO2), which is able to change the phase of the incredible split second, turning from an electrical insulator (dielectric) in the conductor.

The triple point of solid research is extremely difficult, mainly because of the existence of various forms of solid state. It is difficult to get an exact match of interfaces. Theoretically, hidden inside a solid set of triple points, but they are still virtually unexplored, – said David Cobden, a physics professor at the University of Washington.

Cobden is lead author of a paper published in the scientific journal Nature on 22 August 2013 year.

The ability of vanadium dioxide to change the arrangement of electrons that allows the material to move from one state to another (insulator-conductor), was discovered by researchers of the scientific center of Bell Laboratories in 1959. Twenty years later, it became known that there are two slightly differing from each other by insulating states.

New research has shown that these two insulating phase and single conducting phase in vanadium dioxide in solid form can stably coexist at a temperature of 65 degrees Celsius with an accuracy of one-tenth of a degree in one direction or another.

For the detection of the triple point of a team of scientists led by Cobden had to stretch the vanadium dioxide nanowires, observing them under a microscope. It was important not to break the nanoscale wire, which required a specially designed apparatus, the author of the study.

As it turned out, when the triple point of the conductors have lost the ability to stretch and contract. To study the phase transition has been spent for several years. More time is required for the staging of the experiment on the detection of the triple point.

Earlier it was not possible to investigate the properties around the triple point – said the researcher.

Scientists believe that this work is a significant step in the understanding of the phase transition in vanadium dioxide, which can lead to the development of new types of materials.

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