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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.


Spin signal transitioning from being largely independent on the bias current (Id) to linearly dependent on Id when Id increases.(A to J) The voltage detected by the FM contact as a function of in-plane magnetic field measured on device C for representative bias currents (Id) of 0.01 μA (A), −0.01 μA (B), 5 μA (C), −5 μA (D), 10 μA (E), −10 μA (F), 20 μA (G), −20 μA (H), 80 μA (I), and −80 μA (J). The upper and lower sets of traces in (E) show two repeated sets of measurements. The directions of the bias current Id, channel spin polarization S as determined by the spin signal, and Py magnetization M are labeled by the corresponding arrows in (A), (B), (I), and (J). (K) The spin signal δV as a function of the bias current Id. All measurements were performed with a four-terminal configuration at T = 1.6 K.
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Figure 3: Spin signal transitioning from being largely independent on the bias current (Id) to linearly dependent on Id when Id increases.(A to J) The voltage detected by the FM contact as a function of in-plane magnetic field measured on device C for representative bias currents (Id) of 0.01 μA (A), −0.01 μA (B), 5 μA (C), −5 μA (D), 10 μA (E), −10 μA (F), 20 μA (G), −20 μA (H), 80 μA (I), and −80 μA (J). The upper and lower sets of traces in (E) show two repeated sets of measurements. The directions of the bias current Id, channel spin polarization S as determined by the spin signal, and Py magnetization M are labeled by the corresponding arrows in (A), (B), (I), and (J). (K) The spin signal δV as a function of the bias current Id. All measurements were performed with a four-terminal configuration at T = 1.6 K.

Mentions: Figure 3 shows spin potentiometric measurements at T = 1.6 K in another device (“C”; a 30-nm-thick BTS221 flake, with a four-terminal configuration shown in Fig. 2, A and B) at a series of DC bias currents Id increasing from relatively small to very large values (±80 μA), where we found the spin signal transitions from being largely Id-independent to linearly dependent on Id. At a small Id = ±0.01 μA, the spin signal δV is about −0.5 μV for both the positive and negative currents (Fig. 3, A and B), and the trend of the signal is qualitatively similar to those presented in Fig. 1, suggesting a channel spin polarization S along the +y direction and independent of Id. In contrast, at a large Id such as ±80 μA (Fig. 3, I and J), a qualitatively different behavior is observed. Upon reversing Id, the step-like change in the measured spin potential now reverses its trend, and spin signal δV reverses its sign (δV ~1.8 μV for Id = 80 μA and δV ~−2 μV for Id = −80 μA). Such a behavior that δV reverses upon reversing Id is more similar to that studied in previous spin potentiometric measurements on TIs, indicating an Id-induced and reversible helical spin polarization (7, 11, 14). As labeled by the arrows in Fig. 3 (I and J), the direction of S is locked to such a large Id in a way that is consistent with the spin helicity of TSS. At intermediate positive currents (Fig. 3, C and E), the voltage signal exhibits a “transitional” behavior, where the trend of the step-like change undergoes reversals (sometimes even during measurements taken at the same Id; see some examples marked by the brown arrows in Fig. 3, C and E). The dependence of the spin signal δV on Id is summarized in Fig. 3K, where two distinct behaviors are observed: (i) at /Id/ < 5 μA, δV is always negative and relatively constant, about −0.5 μV, independent of both the polarity and amplitude of Id; (ii) at /Id/ > 10 μA, δV reverses its sign with reversing Id and is largely linearly dependent on Id.


Observation of current-induced, long-lived persistent spin polarization in a topological insulator: A rechargeable spin battery
Spin signal transitioning from being largely independent on the bias current (Id) to linearly dependent on Id when Id increases.(A to J) The voltage detected by the FM contact as a function of in-plane magnetic field measured on device C for representative bias currents (Id) of 0.01 μA (A), −0.01 μA (B), 5 μA (C), −5 μA (D), 10 μA (E), −10 μA (F), 20 μA (G), −20 μA (H), 80 μA (I), and −80 μA (J). The upper and lower sets of traces in (E) show two repeated sets of measurements. The directions of the bias current Id, channel spin polarization S as determined by the spin signal, and Py magnetization M are labeled by the corresponding arrows in (A), (B), (I), and (J). (K) The spin signal δV as a function of the bias current Id. All measurements were performed with a four-terminal configuration at T = 1.6 K.
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Figure 3: Spin signal transitioning from being largely independent on the bias current (Id) to linearly dependent on Id when Id increases.(A to J) The voltage detected by the FM contact as a function of in-plane magnetic field measured on device C for representative bias currents (Id) of 0.01 μA (A), −0.01 μA (B), 5 μA (C), −5 μA (D), 10 μA (E), −10 μA (F), 20 μA (G), −20 μA (H), 80 μA (I), and −80 μA (J). The upper and lower sets of traces in (E) show two repeated sets of measurements. The directions of the bias current Id, channel spin polarization S as determined by the spin signal, and Py magnetization M are labeled by the corresponding arrows in (A), (B), (I), and (J). (K) The spin signal δV as a function of the bias current Id. All measurements were performed with a four-terminal configuration at T = 1.6 K.
Mentions: Figure 3 shows spin potentiometric measurements at T = 1.6 K in another device (“C”; a 30-nm-thick BTS221 flake, with a four-terminal configuration shown in Fig. 2, A and B) at a series of DC bias currents Id increasing from relatively small to very large values (±80 μA), where we found the spin signal transitions from being largely Id-independent to linearly dependent on Id. At a small Id = ±0.01 μA, the spin signal δV is about −0.5 μV for both the positive and negative currents (Fig. 3, A and B), and the trend of the signal is qualitatively similar to those presented in Fig. 1, suggesting a channel spin polarization S along the +y direction and independent of Id. In contrast, at a large Id such as ±80 μA (Fig. 3, I and J), a qualitatively different behavior is observed. Upon reversing Id, the step-like change in the measured spin potential now reverses its trend, and spin signal δV reverses its sign (δV ~1.8 μV for Id = 80 μA and δV ~−2 μV for Id = −80 μA). Such a behavior that δV reverses upon reversing Id is more similar to that studied in previous spin potentiometric measurements on TIs, indicating an Id-induced and reversible helical spin polarization (7, 11, 14). As labeled by the arrows in Fig. 3 (I and J), the direction of S is locked to such a large Id in a way that is consistent with the spin helicity of TSS. At intermediate positive currents (Fig. 3, C and E), the voltage signal exhibits a “transitional” behavior, where the trend of the step-like change undergoes reversals (sometimes even during measurements taken at the same Id; see some examples marked by the brown arrows in Fig. 3, C and E). The dependence of the spin signal δV on Id is summarized in Fig. 3K, where two distinct behaviors are observed: (i) at /Id/ < 5 μA, δV is always negative and relatively constant, about −0.5 μV, independent of both the polarity and amplitude of Id; (ii) at /Id/ > 10 μA, δV reverses its sign with reversing Id and is largely linearly dependent on Id.

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.