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Observation of current-induced, long-lived persistent spin polarization in a topological insulator: A rechargeable spin battery

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ABSTRACT

We report a current-induced, persistent, long-lived, and rewritable electron spin polarization in a 3D topological insulator.

No MeSH data available.


Persistent spin signal and its time dependence.(A) Open-circuit voltage detected by the FM contact as a function of the in-plane magnetic B field measured on device F with the source-drain electrical connection open, showing a spin signal δV ~1.3 μV. (B) Open-circuit voltage versus B measured after t = 45 hours. (C) Spin signal δV versus elapsed time t, where δV gradually decreases to ~0.5 μV in the first 3 hours and stays around ~0.6 μV in the next 42 hours. The measurements in (A) to (C) were performed at T = 1.6 K. Inset shows the schematic of the open-circuit measurement in device F. (D) Open-circuit voltage versus B measured at T = 45 K. (E) Open-circuit voltage versus B measured at T = 45 K after t = 10 hours. (F) δV versus t measured at T = 45 K. The directions of Py magnetization M (black arrow) and the inferred channel (top surface) spin polarization S (dashed green arrow) are labeled in (A), (B), and (D).
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Figure 5: Persistent spin signal and its time dependence.(A) Open-circuit voltage detected by the FM contact as a function of the in-plane magnetic B field measured on device F with the source-drain electrical connection open, showing a spin signal δV ~1.3 μV. (B) Open-circuit voltage versus B measured after t = 45 hours. (C) Spin signal δV versus elapsed time t, where δV gradually decreases to ~0.5 μV in the first 3 hours and stays around ~0.6 μV in the next 42 hours. The measurements in (A) to (C) were performed at T = 1.6 K. Inset shows the schematic of the open-circuit measurement in device F. (D) Open-circuit voltage versus B measured at T = 45 K. (E) Open-circuit voltage versus B measured at T = 45 K after t = 10 hours. (F) δV versus t measured at T = 45 K. The directions of Py magnetization M (black arrow) and the inferred channel (top surface) spin polarization S (dashed green arrow) are labeled in (A), (B), and (D).

Mentions: The largely Id-independent spin signal at small Id suggests that it can be observed even with no Id applied. Figure 5A shows the open-circuit voltage measured at T = 1.6 K in device F [a 15-nm-thick flake, with a four-terminal configuration, but only the inner two contacts connected to the voltmeter (inset of Fig. 5C) and the two outer current leads disconnected after measuring an Id-independent spin voltage signal similar to Fig. 1]. The open-circuit voltage exhibits a hysteretic step-like change between the opposite directions of M with δV ~1.3 μV, indicating the presence of a channel spin polarization S even in the absence of any detection current Id. Remarkably, we found that the spin signal is still observable after waiting for t = 45 hours but with a reduced δV (~0.6 μV), as shown in Fig. 5B. The dependence of the spin signal δV on the elapsed time (t) is shown in Fig. 5C, where δV decreases from 1.3 to ~0.5 μV in the first 2 to 3 hours and then stabilizes at ~0.6 μV in the remaining time, suggesting that the channel spin polarization persists for more than 45 hours. We also measured the open-circuit spin signal at an elevated T = 45 K, as shown in Fig. 5 (D to F). At t = 0 hour, a spin signal δV ~0.11 μV can still be observed (Fig. 5D). However, it is no longer detectable after 10 hours (Fig. 5E), indicating that the channel spin polarization has disappeared. The time dependence of the δV shown in Fig. 5F also indicates that δV decays more rapidly with time at T = 45 K compared to that at T = 1.6 K (Fig. 5C).


Observation of current-induced, long-lived persistent spin polarization in a topological insulator: A rechargeable spin battery
Persistent spin signal and its time dependence.(A) Open-circuit voltage detected by the FM contact as a function of the in-plane magnetic B field measured on device F with the source-drain electrical connection open, showing a spin signal δV ~1.3 μV. (B) Open-circuit voltage versus B measured after t = 45 hours. (C) Spin signal δV versus elapsed time t, where δV gradually decreases to ~0.5 μV in the first 3 hours and stays around ~0.6 μV in the next 42 hours. The measurements in (A) to (C) were performed at T = 1.6 K. Inset shows the schematic of the open-circuit measurement in device F. (D) Open-circuit voltage versus B measured at T = 45 K. (E) Open-circuit voltage versus B measured at T = 45 K after t = 10 hours. (F) δV versus t measured at T = 45 K. The directions of Py magnetization M (black arrow) and the inferred channel (top surface) spin polarization S (dashed green arrow) are labeled in (A), (B), and (D).
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Figure 5: Persistent spin signal and its time dependence.(A) Open-circuit voltage detected by the FM contact as a function of the in-plane magnetic B field measured on device F with the source-drain electrical connection open, showing a spin signal δV ~1.3 μV. (B) Open-circuit voltage versus B measured after t = 45 hours. (C) Spin signal δV versus elapsed time t, where δV gradually decreases to ~0.5 μV in the first 3 hours and stays around ~0.6 μV in the next 42 hours. The measurements in (A) to (C) were performed at T = 1.6 K. Inset shows the schematic of the open-circuit measurement in device F. (D) Open-circuit voltage versus B measured at T = 45 K. (E) Open-circuit voltage versus B measured at T = 45 K after t = 10 hours. (F) δV versus t measured at T = 45 K. The directions of Py magnetization M (black arrow) and the inferred channel (top surface) spin polarization S (dashed green arrow) are labeled in (A), (B), and (D).
Mentions: The largely Id-independent spin signal at small Id suggests that it can be observed even with no Id applied. Figure 5A shows the open-circuit voltage measured at T = 1.6 K in device F [a 15-nm-thick flake, with a four-terminal configuration, but only the inner two contacts connected to the voltmeter (inset of Fig. 5C) and the two outer current leads disconnected after measuring an Id-independent spin voltage signal similar to Fig. 1]. The open-circuit voltage exhibits a hysteretic step-like change between the opposite directions of M with δV ~1.3 μV, indicating the presence of a channel spin polarization S even in the absence of any detection current Id. Remarkably, we found that the spin signal is still observable after waiting for t = 45 hours but with a reduced δV (~0.6 μV), as shown in Fig. 5B. The dependence of the spin signal δV on the elapsed time (t) is shown in Fig. 5C, where δV decreases from 1.3 to ~0.5 μV in the first 2 to 3 hours and then stabilizes at ~0.6 μV in the remaining time, suggesting that the channel spin polarization persists for more than 45 hours. We also measured the open-circuit spin signal at an elevated T = 45 K, as shown in Fig. 5 (D to F). At t = 0 hour, a spin signal δV ~0.11 μV can still be observed (Fig. 5D). However, it is no longer detectable after 10 hours (Fig. 5E), indicating that the channel spin polarization has disappeared. The time dependence of the δV shown in Fig. 5F also indicates that δV decays more rapidly with time at T = 45 K compared to that at T = 1.6 K (Fig. 5C).

View Article: PubMed Central - PubMed

ABSTRACT

We report a current-induced, persistent, long-lived, and rewritable electron spin polarization in a 3D topological insulator.

No MeSH data available.