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“Spin Insulatronics"

Date:

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Time:

Thursday, 27 Feb. 2020

Video-Recording for any system with MP4-support

- Video.mp4 (ca.307 Mb)

15:15 – 16:10

Arne Brataas

(Norwegian University of Science and Technology (NTNU))

Abstract:

In magnetic insulators, there are no charge currents, but spin currents can propagate

over long distances. It is the propagation of disturbances in the localized magnetic

moments that can carry spin currents. When magnetic insulators are in contact with

metals, spin-currents can pass from the insulators to the metals via spin-transfer and

spin-pumping enabled by the exchange interaction at the interfaces.

These mechanisms enable electrical control over spin excitations in magnetic insulators.

We will discuss routes for electrical control of quantum coherent magnon phenomena

in magnetic insulators, in ferromagnets and antiferromagnets.

First, we describe the formation of steady-state magnon condensates controlled by a

spin accumulation in adjacent normal metals. Spin-transfer by this spin accumulation

affects the magnetization of the ferromagnet and the staggered field of the antiferromagnet.

The resulting condensation may occur even at room temperature when the spin transfer

to the metal is faster than the relaxation processes in the magnet.

Second, we will discuss how antiferromagnets may exhibit long-range spin superfluidity

in insulators, which studies indicate are good spin conductors. The spin superfluidity can

be detected in non-local geometries and can reach several micrometers.

Third, we will discuss how magnons can mediate superconductivity in adjacent normal

metals. The induced electron pairing is p-wave when the magnetic insulator is ferromagnetic

and d-wave when the magnetic insulator is antiferromagnetic.