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At extremely cold temperatures, things become fascinating. Much like how water turns into ice, some matter undergoes phase transitions that give them interesting properties. Just above absolute zero, for example, aluminum transforms into a superconductor, while helium isotopes change from gas to superfluid. A foundational principle, known as the Kibble-Zurek mechanism (KZM), explains how these materials behave as they cool at different rates.
The KZM has been largely validated for closed systems, or systems confined to the effects of the environment. However, it remains unclear whether the mechanism applies in more realistic scenarios where the environment is at play.
New research by UPD physicists proves that KZM is applicable to a general class of open systems. Moreover, they uncovered subtleties in how phase transitions are studied in laboratories, illuminating possibilities for more precise experiments in condensed matter physics.
“Our work provides a new perspective on how we detect and identify phase transitions in realistic set-ups, in which their interaction with the environment gives us little control over how they will evolve in time,” said Dr. Jayson Cosme and Roy Jara Jr. of the UPD College of Science National Institute of Physics (UPD-CS NIP).
In glassblowing, hot glass is placed in annealers to slow down the cooling process and prevent cracks, while some are briefly dipped in water to create a crackled look. This is similar to materials that follow the KZM: those cooled slowly become homogeneous, while those cooled quickly result in more cracks, or “topological defects.”
In their research, Dr. Cosme and Jara investigated an open system where the cooling rate, or quench speed, is influenced by the environment. “We found that for these systems, the KZM remains valid when the tuning parameter that controls the phase of the system is modified sufficiently slowly,” the researchers said.
However, they observed that KZM breaks down at faster quench speeds. This insight led to a key discovery that a standard laboratory method for detecting phase transitions might not be reliable for open systems undergoing rapid cooling. In the standard method, a threshold is used to infer whether a material has transitioned to a new phase. Dr. Cosme and Jara, however, found that an apparent lag exists between reaching the threshold and the actual phase transition, leading to inconsistencies with the time at which the transition is detected.
“This result is significant as it sheds light on the possible limitations of threshold-based criterion in identifying phase transition when applied to open systems with strong dissipation,” they explained.
As an alternative to threshold-based experiments, they propose using other techniques, such as examining parameters that reach a steady state as the system undergoes phase transition.
While their study applies to a broad class of open systems, they acknowledge that it focuses solely on large systems where quantum effects can be ignored. Since quantum effects may become more relevant for smaller systems, they plan to extend their study to investigate these types as well.
Liquid helium in superfluid phase. (Photo credit: Alfred Leitner)
“We also plan to extend our work to driven systems, where the systems can transition from a stationary to a dynamical phase like the newly discovered phase of matter called time crystals,” they concluded.
By Harvey Sapigao
Ross is known as the Pambansang Blogger ng Pilipinas - An Information and Communication Technology (ICT) Professional by profession and a Social Media Evangelist by heart.
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