The ability to change a material’s properties through phase transitions is increasingly important for the next generation of data storage and computation. Our everyday experience of phase transitions is that they are slow; the ice in our drinks takes a long time to melt, keeping our drinks nice and cold in summer, while a kettle can take a long time to boil water for our cup of coffee. This slowness makes it hard to see how such events could be used in the high-speed computers. However, if phase transitions are driven by laser pulses, rather than temperature changes, they can occur very fast, even on the time scale of a few hundred femtoseconds (1x10^-15s), which is much faster than computers operate.

However, this speed comes at a cost of decreased energy efficiency. Now, an international team of researchers, led by Simon Wall, has found a new way to increase the efficiency of light-induced phase transitions, whilst maintaining the fast-switching nature. If two laser pulses, separate with a delayed of only 150 fs are used, instead of a single pulse, the amount of energy needed to drive the transition could be reduced by 6%. Increasing the delay between the two pulses still resulted in an energy saving, but by a reduced amount.

By exploiting the power of the Japanese X-ray laser, SACLA, the researchers could show that the first laser pulse injects localized structural disorder into the material. These distortions are transient, but if the second laser pulse arrives before they have dissipated, they can act as seeds for the phase transition and reduce the energy barrier.

While more work is needed to understand the processes that occur in order to further improve the efficiency, the method could in principle be applied to a broad range of materials, potentially making future high-speed data storage devices more efficient in the future.

Read the article here: https://www.nature.com/articles/s41567-024-02474-4