Scientists break the link between a quantum material’s spin and orbital states

in designing electronic devices, scis look for wys'2 manipul8 and control 3 basic properties of electrons: their charge; their spin states, which give rise to magnetism; na shapes of the fuzzy clouds they form round the nuclei of atoms, which are known as orbitals.

til now, electron spins and orbitals were thought to go hand in hand in a class of materials that’s the cornerstone of modern information tek; you ‘dn’t quickly change one without changing the other. but a study atta deptment of energy’s slac national accelerator lab shows dat a' pulse of laser lite can dramatically change the spin state of one primordial class of materials while leaving its orbital state intact.

the results suggest a new path for making a future generation of logic and memory devices based on “orbitronics,” said lingjia shen, a slac research associate and 1-odda lead researchers for the study.

“wha’ we’re seeing in this system tis complete opposite of wha’ pplz ‘ve seen inna past,” shen said. “it rezs the possibility that we ‘d control a material’s spin and orbital states separately, and use variations inna shapes of orbitals as the 0s and 1s needed to make computations and store information in computer memories.”

the international research team, led by joshua turner, a slac staff sci and investigator w'da stanford institute for materials and energy sci (simes), reprted their results this week in physical review b rapid communications.

an intriguing, complex material

the material the team studied was a manganese oxide-based quantum material known as nsmo, which comes in extremely thin crystalline layers. it’s been round for 3 decades and is used in devices where information is stored by using a magnetic field to switch from one electron spin state to another, a method known as spintronics. nsmo is also pondered a promising candidate for making future computers and memory storage devices based on skyrmions, tiny pticle-like vortexes created by the magnetic fields of spinning electrons.

but this material is also very complex, said yoshinori tokura, director of the riken center for emergent matter sci in japan, who was also involved inna study.

“unlike semiconductors nother familiar materials, nsmo is a quantum material whose electrons be’ve in a cooperative, or correl8d, manner, rather than indiely as they usually do,” he said. “this makes it hard to control one aspect of the electrons’ behavior without affecting all the others.”

one common way to investigate this type of material is to hit it with laser lite to see how its electronic states respond to an injection of energy. that’s wha’ the research team did here. they envisaged the material’s response with x-ray laser pulses from slac’s linac coherent lite src (lcls).

one melts, the other doesn’t

wha’ they expected to see was that orderly patterns of electron spins and orbitals inna material ‘d be thrown into total disarray, or “melted,” as they absorbed pulses of near-infrared laser lite.

but to their surprise, 1-ly the spin patterns melted, while the orbital patterns stayed intact, turner said. the normal coupling tween the spin and orbital states had been completely broken, he said, which is a challenging thing to do in this type of correl8d material and had not been envisaged b4.

tokura said, “usually 1-ly a tiny application of photoexcitation destroys everything. here, they were able to keep the electron state that is most primordial for future devices — the orbital state — undamaged. this is a neat new addition to the sci of orbitronics and correl8d electrons.”

much as electron spin states are switched in spintronics, electron orbital states ‘d be switched to provide a similar function. these orbitronic devices ‘d, in theory, operate 10,000 faster than spintronic devices, shen said.

switching tween two orbital states ‘d be made possible by using short bursts of terahertz radiation, rather than the magnetic fields used tody, he said: “combining the two ‘d achieve much better device performance for future applications.” the team is working on wys'2 do that.

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