Description
Three-dimensional topological insulators have conductive surface states, whereas the bulk remains insulating. These surface states are spin-momentum locked: a nonzero source-drain bias implies a net spin polarization of the surface charge carriers, and backscattering is forbidden, unless a spin-flip interaction takes place. Spin-flip interactions can for instance take place at magnetic impurities or nuclear spins. Therefore, the net spin polarization of a charge current can, over time, be transferred to an impurity spin polarization boz. Vice versa, thermal relaxation of the impurity spin polarization induces a discharge current. This effect can be modeled by an inductive circuit element, where the induced current is proportional to the nuclear spin flip rate [1, 2]. Elevated temperatures allow for faster discharge, however this is limited by thermally excited bulk carriers shunting the surface state.We experimentally search for current-induced nuclear polarization in the 3DTI (Bi1-xSbx)2Te3 (BST) and magnetic impurity polarization in Vy(Bi1-xSbx)2-yTe3 (VBST). Both BST and VBST films are deposited by molecular beam epitaxy, which allows for tuning the positions of Fermi level and Dirac point through varying the elemental ratios [3, 4]. The experiments focus on two aspects. On one hand, we search for signatures of a nonzero equilibrium impurity spin polarization. For instance, a nonzero impurity spin polarization generates an Overhauser field, which alters the phase coherence length measured in magnetotransport [5]. On the other hand, we search for an induced current due to a changing impurity spin polarization. The results focus on a proof-of-principle. Future developments in topological materials can optimize the inductive effect, potentially leading to a topological inductor.
References
[1] A. M. Bozkurt et al., Phys. Rev. B, 97 (2018) 245414.
[2] A. M. Bozkurt et al., arXiv:2403.00714 (2024)
[3] J. Zhang et al, Nature Communications, 2 (2011) 574
[4] L. Mulder et al., Nanomaterials, 13 (2023) 763.
[5] Z. Jiang et al., Phys. Rev. Lett., 125 (2020) 106902
| Period | 4 Sept 2024 |
|---|---|
| Event title | 31st Conference of the EPS Condensed Matter Division, CMD-31 2025 |
| Event type | Conference |
| Conference number | 31 |
| Location | Braga, PortugalShow on map |