Cracking the Code of the Electron Universe: Researchers Find a Way Around Ohm’s Law

Scientists at Tohoku University and the Japan Atomic Energy Agency have created basic experiments and theories to control the shape of the ‘electron universe’ within a magnetic material under regular conditions. This ‘electron universe’ refers to the arrangement of electronic quantum states, which resembles the structure of the actual universe in mathematical terms.

The studied geometric attribute, known as the quantum metric, was identified through an electric signal separate from typical electrical conduction. Moreover, this discovery uncovers the essential quantum science behind electrons. Furthermore, it sets the stage for creating groundbreaking spintronic devices that leverage the unique conduction arising from the quantum metric.

Exploring the Interplay

Electric conduction, pivotal for numerous devices, traditionally adheres to Ohm’s law, where current varies proportionately to the applied voltage. However, scientists sought to surpass this law to advance into novel device realms. This is where quantum mechanics enters the scene. A distinctive quantum geometry called the quantum metric can induce non-Ohmic conduction. This metric, inherent to the material, implies it’s a foundational feature of its quantum structure.

Quantum Metric and Electron Universe

The term’ quantum metric’ is influenced by the idea of ‘metric’ in general relativity, which describes how the universe’s shape changes due to strong gravitational forces, like those near black holes. Likewise, understanding and using the quantum metric is crucial for creating non-Ohmic conduction in materials. This metric describes the shape of the ‘electron universe,’ similar to the physical universe. The task is to control the quantum-metric structure in a device and see how it affects electrical conduction at average room temperature.

The researchers worked with a thin-film configuration including a heavy metal, Pt, and a special magnet, Mn3Sn, to modify the quantum-metric structure at ambient temperature. When Mn3Sn is next to Pt, it shows significant changes in its magnetic properties when a magnetic field is applied. They observed and controlled a type of non-Ohmic conduction called the second-order Hall effect, where voltage reacts at a right angle and quadratically to the electric current. Theoretical modeling confirmed that the quantum metric solely explains these findings.

Breaking the Barrier: Room Temperature Control of Quantum Metrics

Jiahao Han, the study’s lead author, explained that the second-order Hall effect originates from the quantum-metric structure interacting with the particular magnetic texture at the Mn3Sn/Pt interface. Therefore, he mentioned that they could adjust the quantum metric by altering the material’s magnetic structure using spintronic methods. He further noted that they could confirm such adjustments through magnetic control of the second-order Hall effect.

Yasufumi Araki, the primary contributor to the theoretical analysis, further explained that theoretical predictions suggest the quantum metric as a fundamental concept linking material properties observed in experiments to the geometric structures investigated in mathematical physics. He noted that confirming its evidence in experiments has posed challenges. Araki hoped their experimental method for accessing the quantum metric would further propel theoretical studies in this field.

Principal investigator Shunsuke Fukami also contributed, stating that the quantum metric was previously thought to be intrinsic and beyond control, akin to the universe itself. However, he emphasized the need to alter this perception. Fukami highlighted that their discoveries, especially regarding the adaptable control achievable at room temperature, could open up fresh avenues for future development of functional devices like rectifiers and detectors.

Read the original article on: SciTechDaily

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