Fresh thermometry technique unveils that compressing a gas could result in cooling

A new method of thermometry has been developed by an international research team from Innsbruck and Geneva. This method allows for the measurement of temperatures in low-dimensional quantum gases. Surprisingly, the team discovered that compressing a gas can actually lead to cooling. These groundbreaking results have recently been published in Science Advances.

In our everyday experience, we are accustomed to the idea that compression results in heating, while expansion leads to cooling. This is evident when we pump up a bicycle tire. However, when it comes to the quantum world, things work differently. Quantum physics follows its own set of rules. For instance, bosons, a type of particle, can condense together and become superfluid. On the other hand, fermions, another type of particle, adhere to the Pauli exclusion principle and actively avoid each other.

When we consider reduced dimensions, the situation becomes more complex. Quantum fluctuations play a more significant role, and bosons can exhibit fermion-like behavior when the interactions between particles are extremely strong.

Given these factors, quantum systems in reduced dimensionality have become a fascinating area of research. They serve as a platform for quantum simulation, with particular attention being given to one-dimensional (1D) quantum wires. These wires have garnered widespread interest due to the ongoing miniaturization of electronic circuitry.

To study these quantum systems, researchers utilize cold atoms confined to tightly controlled light potentials. This experimental platform allows for the realization of quantum wires and the simulation of electron properties under strong confinement.

In a collaborative effort between the Department of Experimental Physics in Innsbruck and the Department of Quantum Matter Physics at the University of Geneva, a groundbreaking discovery was made regarding the cooling of a strongly interacting quantum many-body system when its dimensionality is reduced. This unexpected phenomenon, which has not been previously proposed or anticipated in scientific literature, was made possible through the development of a highly effective thermometry method that combines experimental and theoretical approaches, particularly suited for systems with strong interactions.

Yanliang Guo, one of the lead authors of the study, explains, “We have achieved remarkable precision in temperature measurements, with sensitivity down to one nano-Kelvin in one-dimensional systems.” The team observed that when transitioning from three-dimensional to two-dimensional confinement, the temperature initially increases from 12.5 nK to 17 nK, but then decreases to 9 nK upon further compression to one dimension.

This cooling effect arises due to the interplay between strong lateral confinement in one dimension and the presence of strong interactions that lead to bosons fermionizing. The team confirmed that strong interactions in one dimension are a crucial factor for this cooling phenomenon to occur.

Hanns-Christoph Nägerl, one of the team leaders, remarks, “Although the change from 12.5 to 9 nK may not appear significant, our subsequent advancements have allowed us to achieve temperatures as low as 2 nK with a sensitivity of 1 nK.”

The team anticipates that these findings will generate considerable interest within the scientific community. Low-dimensional, strongly correlated quantum many-body systems exhibit a wide range of intriguing quantum effects, and their exploration could provide valuable insights into various unresolved mysteries in physics, particularly the enigma of high-temperature superconductivity, which holds significant implications if solved.

Ultracold atom systems in low-dimensional configurations have become widely utilized as a means of quantum simulation. Notably, significant advancements have been made in the study of 1D systems, such as prethermalization, dynamical fermionization, anomalous heat flow, and spin-charge separation. The measurement of temperature holds immense significance for quantum systems, as emphasized by Hepeng Yao, the lead theorist of this research.

However, the task of measuring temperature in isolated, strongly correlated 1D and 2D quantum many-body systems has remained unaccomplished until now. Thierry Giamarchi, the team leader from Geneva, intriguingly highlights the counterintuitive observation that temperatures may decrease with increased confinement, showcasing the intricate effects that can manifest in the quantum realm.

This article is republished from PhysORG under a Creative Commons license. Read the original article.