Magnetic nanotubes: A new material platform to realize robust spin-Seebeck effect and perfect thermal spin-filtering effect

TL;DR

This study designs boron-nitrogen nanotubes with carbon doping to realize robust spin-Seebeck and thermal spin-filtering effects, demonstrating strain engineering as a means to control these phenomena in spin caloritronics.

Contribution

It introduces a new material platform of boron-nitrogen nanotubes with specific doping and strain strategies to achieve and control spin-Seebeck and thermal spin-filtering effects.

Findings

BNNTs with n=1 show good SSE with symmetric spin currents

Higher carbon doping leads to SSE or SFE depending on symmetry

Strain engineering enhances and switches between effects

Abstract

To construct reliable material platforms and to uncover new rules to realize spin-Seebeck effect (SSE) and thermal spin-filtering effect (SFE) are core topics in spin caloritronics. Here we design several single-layer boron-nitrogen nanotubes (BNNTs) with n boron (nitrogen) atoms substituted by carbons in every unit cell. We find that for n = 1, the magnetic BNNTs generate a good SSE with nearly symmetric spin-up and spin-down currents; while as the carbon dopant concentration increases (c.f. n $\geq$ 2), a high rotational symmetry of the carbons contributes to generate the SSE with more symmetric thermal spin-up and spin-down currents, otherwise towards the thermal SFE. Moreover, some metallic BNNTs can generate the SSE or the SFE with finite threshold temperatures, due to the compensation effect around the Fermi level. More importantly, we find that the compression strain engineering is an effective route to improve these effects and to realize the transition between them. These theoretical results about the SSE in nanotubes enrich the spin caloritronics, and put forwards new material candidates to realize the SSE and other inspiring thermospin phenomena