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Mysterious object caused by spontaneous symmetry breaks revealed.



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Figure 1: Composite defects in superfluid 23Na confined to Pancake-shaped two-dimensional “electromagnetic vessel” A darker color indicates an area with high liquid density. The core of the topological defect corresponds to the white area in the center of the image. Credits: Physiology, Rev. Lett. 122, 095301 (2019)

Hiromitsu Takeuchi, a professor at the Graduate School of Science, Osaka City University and a researcher at the Nambu Yoichiro Institute of Theoretical and Experimental Physics (NITEP), has theoretically identified the nature of the mysterious topological defect that caused by objects that are not Spontaneous symmetry breaking time equilibrium (SSB) evolution Since the SSB perceived in this system is the same as the SSB known to occur in isotropic superconductors and superfluid 4He, it is expected to produce a spontaneous symmetrical break-time equilibrium (SSB). The topological defects with vortex-like properties in the fluid are called quantum eddy currents. However, the topological defects observed in this experiment are structurally less similar to the previously mentioned SSB. and its physical properties are shrouded in mystery. In this research The idea of ​​applying the Joukowski transform, which is used to calculate the lift of an aircraft wing with quantum eddy currents, was introduced for the first time. And the analysis revealed that the most stable state of this mysterious topological flaw was something new. A topological defect known as a quantum elliptical vortex. The results of this research are published online in physical review letterIt is considered one of the most famous journals in physics.

Generally, time and space-dependent functions known as “fields” are used to describe the properties of the physical system in which SSBs arise if field motion can be calculated. The behavior of the system can also be predicted. However, general calculations are difficult because the degree of field independence is infinite.

One effective way to describe the complex motion of a field is to show the degree of freedom of an object suspended in it. This is called a topological defect. The field around the “axis” of a topological defect has a certain structure. Therefore, by describing the center of the core as the motion of a point of mass, Field movements are approximate.

This situation is similar to the future wind direction change that can be predicted to some extent based on the typhoon eye path. In materials that often form SSB, such as superconductors and superfluids, this “wind” corresponds to non-resistive and frictionless currents, respectively, since the structure of the field around the core can be predicted by symmetrical breaks. It is therefore believed that the behavior of topological defects and hence field behavior can be understood if symmetric fractures are understood on a global scale.

Mysterious object caused by spontaneous symmetry breaks revealed.

Fig. 2: Flow (numerical computation) around a simple rotating symmetrical quantum vortex (left) and a quantum elliptical vortex (right). An arrow indicates the direction of flow. The more white, the stronger the flow. The outline of the core is outlined in dotted lines. The background color represents the θ phase of the macro wave function. (complex function) corresponding to the superfluid field. Credit: Osaka City University

This refuting phenomenon was recently discovered by Professor Shin’s experimental group at Seoul National University. [Phys. Rev. Lett. 122, 095301 (2019)]. Because the broken symmetry in this experimental system is similar to that of the well-known conventional superconductors and superfluids. The shape of the core of a topological defect known as a quantum vortex is therefore expected to be round like a typhoon’s eye in two – dimensional cross-sections.

However, the actual cross-sectional structure of the observed phase defects is completely different. Fig. 1 shows an experimental photograph of the structure corresponding to the cross-section of the topological defect caused by the abrupt phase shift in At that time, this topological defect was considered a compound of two known topological defects. It is a composite defect (composite defect) and is interpreted as a transient state that occurs during the phase transition process near the critical point.

in this study To clarify the physical properties of the composite defects observed in the experiment, Hiromitsu Takeuchi introduced the idea of ​​applying the Joukowski transform, which is used to calculate the lift of an aircraft wing against a quantum vortex. The topological observed in the experiments eventually stabilized. It is a new topological defect known as a quantum elliptical vortex. Conventional quantum vortexes have a rotating symmetrical flow in cross-section. Like the eye of the typhoon (Fig. 2, left), however, the newly proposed cross-sectional image of the quantum elliptical current breaks the natural rotation symmetry and creates a current along the ellipse. It was previously thought that the outward appearance of a topological defect was determined by considering how the global SSB of the physical system occurs. But this result clearly reverses that perception.

It is theoretically known that such peculiar structures occur near the critical point of phase transition, and that SSB in the region within the core of the topological fault is heavily involved in its stability.

Although SSB has been studied for a long time But there is still no general understanding of how SSB inside the core occurs. and how does it affect the physical properties of topological defects? Topological defects do not only appear in specialized materials such as superconductors. But also in a wide variety of physical systems, from relatively familiar materials such as crystals and liquid crystals to cutting-edge science and technology such as spintronics, and are considered to play an important role. in the revolving neutron stars and their phase changes in the early universe. It is hoped that new developments in SSB, such as Takeuchi’s discovery, will arise from improvements in experimental techniques and related theoretical advances. and will affect the whole field of physics


A new direction of topological research is now ready for flight.


More information:
Hiromitsu Takeuchi, Quantum Elliptic Vortex in Nematic-Spin Bose-Einstein condensate, physical review letter (2021). doi: 10.1103/PhysRevLett.126.195302

Provided by Osaka City University

reference: Mysterious object caused by Spontaneous Symmetry Revealed (2021, June 10). Retrieved June 10, 2021 from https://phys.org/news/2021-06-mystery-spontaneous-symmetry-revealed.html.

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