Researchers Reveal 'Hidden' Phases of Matter

Saturday, June 15, 2019 - 15:43

Researchers have recently found out that a metal oxide has a "hidden" phase, one that gives the material new, ferroelectric properties, the ability to separate positive and negative charges, when it is activated by extremely fast pulses of light.

The findings of the research, led by MIT researchers Keith A. Nelson, Xian Li, and Edoardo Baldini, in collaboration with Andrew M. Rappe and Penn graduate students Tian Qiu and Jiahao Zhang, were published in Science.

In addition to changing electric potential, this approach could be used to change other aspects of existing materials—turning an insulator into a metal or flipping its magnetic polarity, for example.

The group studied strontium titanate, a paraelectric material used in optical instruments, capacitors, and resistors. Strontium titanate has a symmetric and nonpolar crystal structure that can be "pushed" into a phase with a polar, tetragonal structure with a pair of oppositely charged ions along its long axis.

They found that when strontium titanate is excited with light, the ions are pulled in different directions, with positively charged ions moving in one direction and negatively charged ions in the other.

Then, instead of the ions immediately falling back into place, the way a pendulum would after it's been pushed, vibrational movements induced in the other atoms prevent the ions from swinging back immediately.

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کد خبر: 656650 0 0

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