Giant Spontaneous Hall Effect Without a Magnet

Surprising phenomenon in the solid state physics was “The Hall effect, which requires normally magnetic fields, can also be generated completely in a different way by without the magnet to give an extreme strength” – Published by Sami Dzsabera et al., in the Proceedings of the National Academy of Sciences, on 19^th February 2021.

Weyl–Kondo semimetal have been discovered recently, the three-dimensional (3D) Dirac cones that describes with massless relativistic quasiparticles, which was stabilized by breaking via either time-reversal symmetry (TRS) or inversion symmetry (IS).

Sami Dzsabera et al., have reported the discovery of a giant spontaneous Hall effect in 3D materials, which have not only identifies an ideal technique. However, it will demonstrates a strong correlations that can drive extreme topological responses, which we can expect to trigger for future work. Further, they reported that the giant spontaneous Hall effect of semimetal seems to be the non-centrosymmetric and non-symmorphic heavy fermion, which can be identified as a candidate Weyl–Kondo semimetal. However, it preserves time-reversal symmetry. This can be attributed to the finding of Weyl nodes, due to the Kondo interaction–singularities of the Berry curvature–which emerges on the immediate vicinity of the Fermi level. Also, they have observed that the stress phenomenon is been distinct from the previously detected anomalous Hall effect in materials of broke time-reversal symmetry. However, it has been manifested an extreme topological response, which requires a beyond-perturbation-theory description. The main motivational points in this present work is to scrutinize this interpretation via, more direct probes of topology. Even tiny electric and zero magnetic fields will have a large magnitude of the effect as well as its robust bulk nature, which may aid the exploitation in topological quantum devices [1].

Significance

Traditional classification of states of matter on their symmetry, has been exemplified by the distinction of a solid and a liquid. On the other hand, the topological quantum phases, are very hard to identify and characterize, especially in the electronic systems with strong correlations. Hence, the results will enable the identification of the electronic topological states that are correlated with quantum materials, which may trigger the effort towards the exploitation of robust quantum electronics [1].

Normally, when the electric current is deflected by a magnetic field, the conducting materials will lead, which is termed as ‘Hall effect’. This Hall effect is generally used to measure magnetic fields. Discovery of a new exotic metal was made with cerium, bismuth and palladium (Ce₃Bi₄Pd₃) that has been examined with a giant Hall effect produced by the material, in the absence of the magnetic field [2].

Figure 1. Material behaves like the presence of magnetic monopoles without any magnet. Credit: TU Wien

The main reason for this unexpected result is due to the unusual behavior and properties of the electrons. They behave like magnetic monopoles were already present in the material. Further, the measurements showed that the material exhibits Hall effect without any external magnetic field. Hence, it is not an usual normal Hall effect, on which its strength can be produced with an enormous of electromagnetic coils, however with a huge one [2].

However the main question raised was “If a Hall effect occurs without an external magnetic field, perhaps we are dealing with an extremely strong local magnetic fields that occur on a microscopic scale inside the material, but can no longer be felt outside?” —Silke Bühler Paschen.

Further investigations was carried out and found that the elementary particles are well suited for investigating magnetic phenomena and the resultant material was examined.

“If there is no any magnetic field, then there will be no any Lorentz force which can act on the electrons in the material – but nevertheless a Hall effect was measured which is really a remarkable” —Silke Bühler Paschen.

For simpler materials, the prediction of this effect was made theoretically, however, no one can able to prove it. The major breakthrough was obtained, in the present investigation with a new class of materials was the chemical composition of Ce₃Bi₄Pd₃ is characterized via a strong interaction between the electrons which is known as the “Kondo effect” —Silke Bühler Paschen.

This Kondo effect mainly causes the fictitious magnetic monopoles to have exactly the right energy to influence the conduction electrons in the material extremely strong. Hence, this would be the major reason, why the effect is more than a thousand times larger than predicted theoretically values?

For the next-generation quantum technologies, these new giant spontaneous Hall effect will holds some potential. For instance, a non-reciprocal elements will produce direction-dependent scattering entirely without an external magnetic field, which they could be realized with this effect.

“The extremely non-linear behavior of the material is also of great interest" - Silke Buhler Paschen.

Our SNB team have mainly emphasize this new research article to enrich our viewer’s knowledge about the Hall effect measurements with a giant berry curvature contribution (in a time-reversal invariant material), on the non-centrosymmetric heavy fermion semimetal Ce₃Bi₄Pd₃. The Hall effect is enhanced via the orders of magnitude over the expected values for weakly interacting systems, where the Hall angle is applied to an electric field. This can be attributed due to the effect of tilted and highly Weyl nodes that can emerge very close to the Fermi surface from the Kondo effect. The main criteria is that the complex of many-particles phenomena in solid states, this may give rise to unexpected application possibilities that can make the research field exciting. Hence, there is a need of a systematic analysis on the interplay between topology and strong correlations thereby enabling the heavy fermion compounds or with the other classes of materials. Further, they discovered the effect on a 3D material, when there is an absence in the magnetic fields under the tiny driving electric fields, that holds better performance for the topological quantum devices development. Thus, their research findings will provide a better window into the landscape of “extreme topological matter”, where there can be a strong correlations that can lead to an extreme topological responses, which would be an evitable one in the near future.

References

S. Dzsabera et al., Proceedings of the National Academy of Sciences, (2021), DOI: 10.1073/pnas.2013386118.
https://scitechdaily.com/surprise-in-solid-state-physics-magnetic-effect-without-a-magnet/.

Dr. Y. Sasikumar

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