Open Access
Add to BibSonomy
Abstract
The photoinduced inverse spin Hall effect (PISHE) has been studied in three dimensional (3D) topological insulator (TI) Bi2Te3 thin films with different thicknesses (3, 5, 12 and 20 quintuple layer (QL)). The sign of the PISHE current flips only once in the 3- and 20-QL Bi2Te3 films, but it flips three times in the 5-, 7- and 12-QL samples. The three-times sign flip is due to the superposition of the PISHE current of the top and bottom surface states in Bi2Te3 films. By analyzing the x-ray photoelectron spectroscopy (XPS) of the Bi2Te3 films, we find that the top surface of the 3- and 20-QL Bi2Te3 films are severely oxidized, leading to only one sign flip in the PISHE. The PISHE contributed by the top and bottom surface states in Bi2Te3 films have been successfully separated by fitting a theoretical model to the PISHE current. The impact of the bulk states on PISHE current has been determined. The PISHE current is also measured at different light powers, and all the measurement results are in good agreement with the theoretical model. In addition, it is found that the PISHE current in Bi2Te3 films grown on Si substrate is more than two orders larger than that grown on SrTiO3 substrates, which can be attributed to the larger absorption coefficient for Bi2Te3/Si samples. It is revealed that the PISHE current in 3D TI Bi2Te3 is as large as 140 nA/W in the 3-QL Bi2Te3 film grown on Si substrate, which is more than one order larger than that reported in GaAs/AlGaAs heterojunction (about 2 nA/W) and GaN/AlGaN heterojunction (about 1.7 nA/W). The giant PISHE current demonstrates that the TIs with strong SOC may have good application prospects in spintronic devices with high spin-to-charge conversion efficiency.
© 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Manipulations and conversions between spin and charge currents are the core topics of spintronics. The inverse spin Hall effect (ISHE), which converts a spin current into a charge current, provides a powerful tool to detect spin current and spin accumulation electrically [1]. The ISHE describes the phenomenon that an electrical current or electromotive force is created perpendicularly to the flow of the spin-polarized current, which is due to the strong spin-orbit coupling (SOC) [2]. There are two mechanisms proposed theoretically for ISHE, i.e., the extrinsic and intrinsic mechanisms, respectively. The former one is based on asymmetric Mott-skew or side-jump scattering from impurities in a SOC system [3], while the latter one is dependent only on the band structure of the perfect crystal, which arises from Rashba or Dresselhaus SOC [4,5]. The ISHE have been widely studied in metallic films, semiconductors and their heterojunction, such as Pt, Ta, ZnO, Si, GaAs, Pt/Ge, Pt/GaAs, GaN/AlGaN, and GaAs/AlGaAs two-dimensional electron gas [6–14].
Recently, three-dimensional (3D) topological insulators (TIs), such as Bi$_2$Se$_3$, Sb$_2$Te$_3$, and Bi$_2$Te$_3$, have received a great deal of interest recently in spintronics due to the spin-momentum locked Dirac surface states [15–20]. 3D TIs exhibit very strong SOC and nontrivial topological surface states, which makes them appropriate to achieve a large ISHE [4,20]. A large ISHE has been observed by using spin pumping from a Fe/Bi$_2$Te$_3$ heterostructure [18]. Besides, the ISHE has also been observed in Bi$_2$Se$_3$ thin film by excitation of circularly polarized light [19], i.e., by photoinduced inverse spin Hall effect (PISHE). The PISHE provides an effective and convenient way to investigate the ISHE [10,11,21] which can be observed even at room temperature without introducing ferromagnetic elements and external magnetic field. Although the PISHE of the top surface states has been successfully separated in Bi$_2$Se$_3$ thin film [19], the influence of the bulk states and thickness on the PISHE is still unknown.
In this paper, we investigated the PISHE of 3D TI Bi$_2$Te$_3$ thin films with different thicknesses. By model fitting, the PISHE of the top and bottom surface states have been successfully separated. Besides, the influence of the bulk states on the PISHE has also been discussed. As the light spot was moved from the left to the right side of the two contacts, the sign of the PISHE current in the 5-, 7- and 12-QL samples flipped three times, which was due to the superposition of the PISHE of the top and bottom surface states in Bi$_2$Te$_3$ films. However, the sign of the PISHE current in the 3- and 20-QL samples only flipped once. This may be attributed to the severely oxidation of the top surface states in the 3- and 20-QL samples, which was confirmed by the x-ray photoelectron spectroscopy (XPS) analysis. Besides, we also measured the PISHE current under different light powers, which showed good consistence with the theoretical model. In addition, we found that the PISHE current of the Bi$_2$Te$_3$ films grown on Si substrate was more than two orders larger than that grown on SrTiO$_3$ substrates, which might be due to the the larger absorption coefficient for Bi$_2$Te$_3$/Si samples. The giant PISHE in Bi$_2$Te$_3$ films suggest that 3D TIs Bi$_2$Te$_3$ films may have good application prospects in spintronic devices with high spin-to-charge conversion efficiency.
2. Samples and experiments
The experiments were carried out on Bi$_2$Te$_3$ thin films with a thickness of 3, 5, 7, 12 and 20 QL grown on insulating Si (111) substrates by molecular beam epitaxy (MBE). To study the influence of substrates on PISHE, a Bi$_2$Te$_3$ thin film of 7 QL grown on SrTiO$_3$ (STO) substrate was also investigated. A pair of Ti/Au ohmic contacts of about 0.5$\times$0.5 mm$^2$, with a distance of about 1 mm were deposited on the surface of Bi$_2$Te$_3$ film by electron beam evaporation. To prevent the oxidation of the samples in air, the samples were mounted on an optical cryostat chamber with a 1 Pa low pressure, which also allows the variation of temperature from 77 to 300 K.
A diode-pumped solid-state laser with a wavelength of 1064 nm was used as a radiation source. The laser beam passed through an attenuator, a chopper, a polarizer and a quarter-wave plate, and then irradiated normally on the sample, as shown in Fig. 1(a). The diameter of the light spot on the sample was about 0.5 mm, and the light spot had a Gaussian profile. The power of the laser can be changed by rotating the optical attenuator. By rotating the quarter-wave plate, the helicity of the light can be modulated from right circularly polarized to linearly polarized, to left circularly polarized, periodically. The photocurrent was collected by the two contacts with a preamplifier and a lock-in amplifier. The reference frequency of the lock-in amplifier came from the chopper, which was adopted to be 229 Hz. In the experiments, we measured the PISHE current as a function of light spot positions, i.e., we measured the PISHE current when the light spot was moving along the perpendicular bisector of the connection of the two contacts. During the scanning of the laser spot along the perpendicular bisector of the two contacts, to eliminate the influence of the thermoelectric effect, the laser should irradiate the sample symmetrically in which the distance from the center of the laser spot and two contacts should be always equal.
Fig. 1. (a) Experimental set-up used to measure the PISHE current. (b)-(e) Dependence of the photocurrent on the quarter-wave plate when the laser is illuminated at point A, B, C and D of the 5-QL Bi$_2$Te$_3$ film grown on Si substrate, respectively. The power of the light illuminated on the sample is 50 mW. The circles are the experimental data, and the solid lines are the fitting curves by using Eq. (1). The blue and green dotted lines indicate the components of $L_1\sin 4\varphi +J_0$ and $L_2\cos 4\varphi +J_0$, respectively, and the dashed lines represent the component of $J_{\rm {PISHE}}\sin 2\varphi +J_0$. The dash-dotted line is the polarization independent photocurrent $J_0$. (f) Dependence of the PISHE current on the light spot position for the 5-QL Bi$_2$Te$_3$ film grown on Si substrate.
The generation process of PISHE current is as follows. Under the illumination of the circularly polarized light with a Gaussian profile, spin polarized carriers with Gaussian distribution are generated in the space of the unsaturated absorption area. A diffuse spin current $J_s$ which flows along the radial direction will be induced because of the concentration gradient of the photo-generated carriers. Due to the ISHE or the spin-momentum locking effect of the surface states in TIs, the spin polarized carriers will experience a spin transverse force along the axial direction, resulting a a swirly current around the light spot. This photocurrent is called PISHE current [10,19,21].
The PISHE current can be obtained by fitting the light polarization state-dependent photocurrent $J$ to the following equation: [10,19,21]
Here, $J_{\rm {PISHE}}$ indicates the PISHE curent, and $L_1$ and $L_2$ are the photocurrent induced by linearly polarized light, which may be attributed to the optical momentum alignment effect [22,23]. $J_0$ is the helicity-independent photocurrent, due to the thermoelectric effect, photovoltaic effect, and the Dember effect [19,21].3. Result and discussion
3.1 PISHE current of Bi$_2$Te$_3$ films with different thicknesses
Figure 1(b)–1(e) show the dependence of the photocurrent on the quarter-wave plate when the laser is illuminated at point A, B, C and D for the 5-QL Bi$_2$Te$_3$ film grown on Si substrate, respectively. Here $x$ = 0 means the light spot is located at the midpoint of the connection line between the two contacts. The solid lines are the fitting results by using Eq. (1), and the dashed red lines indicate the component of $J_{\rm {PISHE}}\sin 2\varphi$. It can be seen that, as the light spot is moving from the left to the right side of the two contacts, the sign of the PISHE current flips three times. This can also be clearly seen in Fig. 1(f), which shows the dependence of the PISHE on the light spot position. This phenomenon can be attributed to the superposition of the PISHE of the top and bottom surface states, since the top and bottom surface states possess opposite spin helicity. The similar phenomenon had been observed in Bi$_2$Se$_3$ film [19], which was attributed to the superposition of the top surface states and the two-dimensional electron gas (2DEG) beneath the top surface states. However, the Rashba splitting of our Bi$_2$Te$_3$ samples is quite small, which can be evident from the angle-resolved photoemission spectroscopy (ARPES) of the 7-QL Bi$_2$Te$_3$ film grown on Si, as shown in Fig. 2(a). In addition, similar PISHE curve is observed in the 7-QL Bi$_2$Te$_3$ film grown on STO substrates (see Fig. 7(b)), but no Rashba splitting is observed in the ARPES, as shown in Fig. 2(b). Besides, the temperature dependence of the PISHE in Bi$_2$Te$_3$ films suggests that the PISHE may come from the surface states rather than the 2DEG (see below discussion). Therefore, the contribution of the 2DEG can be ruled out.
Fig. 2. ARPES band map of the 7-QL Bi$_2$Te$_3$ film grown on (a) Si and (b) STO substrate, respectively. (c) Schematic diagram of the optical transitions for the top and bottom surface states under illumination of circularly polarized light of 1064 nm.
To further explain the origin of the PISHE current, a schematic of the optical transitions in the top and bottom surface states of Bi$_2$Te$_3$ has been presented, as illustrated in Fig. 2(c). The direct optical transitions of electrons around Fermi level in Bi$_2$Te$_3$ will occur under the illumination of circularly polarized light of 1064 nm. Specifically speaking, the spin electrons in the first conduction band (CB1) and first topological surface state (SS1) with angular momentum $j = +1/2$ will jump to the second topological surface state (SS2) with $j = -1/2$. Due to the top and bottom surface states in Bi$_2$Te$_3$ have opposite SOC coefficient, the spin electrons will flow at an opposite direction due to ISHE, leading to the PISHE current at top and bottom surface has an opposite sign, which are in good agreement with the experimental observation.
Figure 3(a) shows the PISHE as a function of the light spot position for the Si substrate and the Bi$_2$Te$_3$ thin films of 3, 5, 7, 12, and 20 QL grown on Si substrate, which are illuminated by 1064 nm light of 50 mW. One can see that there is also PISHE current in the Si substrate, which may be induced by the SOC due to the residual stress in the Si substrate. However, the intensity of the PISHE in the Si substrate is much smaller than that in the Bi$_2$Te$_3$ samples, and its sign of the PISHE is opposite to that of the Bi$_2$Te$_3$ films. Therefore, it can be inferred that the PISHE of Bi$_2$Te$_3$ samples is mainly contributed by the Bi$_2$Te$_3$ rather than the Si substrate. Subtracting the PISHE of the Si substrate, we obtain the PISHE current that solely comes from Bi$_2$Te$_3$ films, as shown in Fig. 3(b). It can be seen that the curves are more symmetrical between the $+x$ and $-x$ regions compared with that without subtracting the PISHE of the Si substrate. It can be seen that the PISHE current in the 3-QL Bi$_2$Te$_3$ grown on Si substrate is as large as 140 nA/W, which is more than one order larger than that reported in GaAs/AlGaAs heterojunction (about 2 nA/W) [11] and GaN/AlGaN heterojunction (about 1.7 nA/W) [10]. The giant PISHE value observed in the 3D TI Bi$_2$Te$_3$ suggest that 3D TIs Bi$_2$Te$_3$ films may have good application prospects in spintronic devices with high spin-to-charge conversion efficiency.
Fig. 3. (a) PISHE current as a function of light spot position for the Si substrate and the Bi$_2$Te$_3$ films of 3, 5, 7,12, and 20 QL under excitation of 1064 nm light of 50 mW. (b) PISHE current as a function of light spot position for the Bi$_2$Te$_3$ films with the PISHE signal of the Si substrate being subtracted.
3.2 Separation of the PISHE of the top and bottom surface states
To separate the PISHE of the top and bottom surface states, we propose a model based on that reported in Ref. [19]. Specifically speaking, under the radiation of a laser with a Gaussian profile $G(r)=\frac {1}{\sqrt {2\pi }\sigma }\exp (-\frac {r^2}{2\sigma ^2})$, a spin current flowing along the radial direction will be induced, which can be expressed as $j_r=\tau _sD\nabla _r G(r)$. Here, $D$ is the spin diffusion coefficient, $\tau _s$ is the spin relaxation time, $r$ denotes the radial direction, and $\sigma$ indicates the distribution variance related to the full-width at half maximum (FWHM) of the light intensity. Due to the ISHE effect, the spin polarized carriers will experience a spin transverse force $f(r)\propto j_r\times \hat {z}$ [10,24], which can be expressed as $f(r)=-f_0r/\sigma ^3\exp (-\frac {r^2}{2\sigma ^2})$. Here $f_0$ is the spin transverse force constant associated with SOC of the material system. Then, the total PISHE current collected by the two contacts can be expressed as
It is worth mentioning that the integral in Eq. (2) should be performed in the absorption unsaturation region, because there is no PISHE current in absorption saturation area. To determine the radius $r_s$ of the absorption saturated area, we propose the following assumptions. Firstly, in the absorption unsaturated area, the light absorbed by the first conducting layer is proportional to the light intensity, and in the absorption saturated area, the light intensity absorbed by the first conducting layer is a constant. Thus, in the absorption unsaturated area, the light that penetrates through the first conducting layer and reaches at the second conducting layer can be expressed as $k_1 I_0$. Here $I_0$ is the intensity of light that reaches at the first conducting layer, and $k_1$ is the transmission coefficient of the light for the first conducting layer. Secondly, the absorption saturation intensity $Q_s$ is a constant for a certain conducting layer of the Bi$_2$Te$_3$ sample, and the relationship between $Q_s$ and light power $P_0$ can be expressed as
Here $G(r)$ is a Gaussian function which describes the profile of the light spot. $n$ is a fitting parameter. $\sigma$ is the distribution variance related to the FWHM of the light intensity, and $r_s$ indicates the radius of the absorption saturated area. Therefore, by fitting Eqs. (2)–(4) to the experimental data, we can separate the PISHE and obtain the parameter $f_{0i}/R_i$ of the top and bottom surface states, respectively.Figure 4(a)–4(e) shows the fitting results for the 3-, 5-, 7-, 12-, and 20-QL samples by using Eqs. (2)–(4) to the experimental data. The squares are the experimental data, and the solid lines are the fitting curves. The red dashed and blue dotted lines indicate the PISHE current of the top and bottom surface states, respectively. It can be seen that the experimental data can be well fitted by the theoretical model. The fitting parameters are summarized in Table 1. In the fitting, $\sigma$ is adopted to be 0.3 mm, which is measured experimentally. The parameter $f_{0}/(q\cdot R)$ for the top and bottom surface states are also shown in Fig. 4(f). It can be seen that for the 3- and 20-QL samples, the $f_{0}/(q\cdot R)$ is fitted to be zero, which may be attributed to the severe oxidation of the top surface states as confirmed by the XPS measurements (see below discussion). For the 5-, 7-, and 12-QL samples, the fitted $f_{0}/(q\cdot R)$ of the top surface states shows the same value. However, for the bottom surface states, the fitted $f_{0}/(q\cdot R)$ decreases with the increasing thickness of Bi$_2$Te$_3$ films. There are two possible reasons for this phenomenon. The first one is due to the increase of the thickness, the light that can reach at the bottom surface states is reduced, leading to the decrease of the parameter $f_{0}/(q\cdot R)$. The second possible reason is that the bulk states may also generate PISHE current, which may show an opposite sign with that of the bottom surface states.
Fig. 4. Dependence of the PISHE current on the light spot positions for the (a) 3-, (b) 5-, (c) 7-, (d) 12-, and (e) 20-QL Bi$_2$Te$_3$ films on Si substrates. The solid symbols indicate experimental data, and the solid lines represent the fitting results by using Eqs. (2)–(4). The red dashed and blue dotted lines are the PISHE current of the top and bottom surface states obtained by model fitting. (f) Dependence of the $f_{0}/(R\cdot q)$ on the thickness of the films for the top and bottom surface states, which are obtained by model fitting.
Table 1. Fitting parameters of experimentally measured PISHE current.
Now let us estimate the influence of the bulk states. Given that the top surface states of the Bi$_2$Te$_3$ films of different thicknesses show the same value of $f_{0}/(q\cdot R)$, it is reasonable to assume that the bottom surface states also show the same value of $f_{0}/(q\cdot R)$ for different thicknesses, if the influence of the bulk states is eliminated. Considering the top or bottom surface states have a thickness of about 1 QL, the thickness for bulk states in the 3-, 5-, 7-, 12- and 20-QL samples are 1, 3, 5, 10 and 18 QL, respectively. Denoting the $f_{0}/(q\cdot R)$ of the bottom surface states to be $X_2$, and that of the bulk states per QL to be $X_b$, we have
which are obtained by the 3- and 20-QL samples, respectively. From Eqs. (5) and (6), we have $X_2$ = −7.794$\times$10$^{-9} N/(C\cdot \Omega )$ and $X_b$ = 0.194$\times$10$^{-9}\; N/(C\cdot \Omega )$. Then, by the following equations, i.e., $X_2+3X_b$, $X_2+5X_b$, and $X_2+10X_b$, we can calculate the $f_{0}/(q\cdot R)$ of the bottom surface states for the 5-, 7- and 12-QL samples, with the influence of the bulk states taken into account, to be −7.21$\times$10$^{-9}$, −6.82$\times$10$^{-9}$, and −5.85$\times$10$^{-9}\;N/(C\cdot \Omega )$, respectively. These values show good agreement with that obtained by fitting, as shown in Table 1, suggesting that the model are reliable.To find out the reason for the only one sign flip in the PISHE curve in the 3- and 20-QL samples, we perform the XPS measurements for the 3-, 7- and 20-QL samples, and the results are shown in Fig. 5. One can see that, compared with the 7-QL sample, the intensity of the oxide species in the 3- and 20-QL Bi$_2$Te$_3$ films is much larger than that of the corresponding metal peaks, indicating that the top surface of the 3- and 20-QL samples is severely oxidized. As a result, the PISHE peak for the top surface states may not appear, and only that of the bottom surface states presents, leading to only one flip in the sign of the PISHE for the 3- and 20-QL samples.
Fig. 5. XPS analysis of the Bi$_2$Te$_3$ thin films with a thickness of 3, 7 and 20 QL on Si substrates. (a) - (c) The Te 3$d$ peaks of the 3-, 7- and 20-QL samples. (d) - (f) The Bi 4$f$ peaks of the 3-, 7-and 20-QL samples.
3.3 Power and temperature dependence of the PISHE current
Figure 6(a)–6(c) shows the PISHE current as a function of light spot positions under excitation of different light powers. The solid symbols are the experimental data, and the lines are the theoretical fitting results. The PISHE values around the peak $x = \pm 0.4$ mm and $x=\pm 1.3$ mm are summarized in Fig. 6(d), and the solid and dashed lines in Fig. 6(d) are the theoretical calculation results of the model described in section 3.2. In the fitting, the parameter $n$ in Eq. (4) is fitted to be 3. One can see that the PISHE current almost increases linearly with the light power. It can be seen that the experimental data measured under different light powers can be well fitted by the theoretical model, which confirms the reliability of our model.
Fig. 6. PISHE current of the Bi$_2$Te$_3$ film with a thickness of (a) 3, (b) 5, and (c) 7 QL under different excitation powers. (d) Dependence of the PISHE current on light power when the light spot is located at $x$ = $\pm$ 0.4 mm and $x$ = $\pm$1.3 mm. The solid symbols are experimental data, and the lines are the theoretical calculation results.
Fig. 7. (a) PISHE current of the 7-QL Bi$_2$Te$_3$ film on Si substrate as a function of light spot positions measured at different temperatures. (b) PISHE current of the 7-QL Bi$_2$Te$_3$ film grown on Si and SrTiO$_3$ substrates, respectively, as a function of light spot positions.
Figure 7(a) shows the temperature dependence of the PISHE current of the 7-QL Bi$_2$Te$_3$ film grown on Si substrate. It can be seen that, the PISHE current almost does not change with temperature in the range of 300 to 130 K. This phenomenon may suggest that the spin relaxation time of the photo-excited carriers is almost independent of temperature, given that the PISHE current is proportional to the spin relaxation time of the photo-excited carriers. It has been reported that the spin relaxation time of the Dirac surface states is almost independent of temperature, while that of the bulk states significantly decreases with increasing temperature [25]. Therefore, the observation that the PISHE current almost independent of temperature may suggest that the PSIHE current is contributed by the surface states instead of the bulk states or 2DEG.
3.4 Comparison of the PISHE current for Bi$_2$Te$_3$ films grown on different substrates
Figure 7(b) shows the PISHE current as a function of light spot positions for the 7-QL Bi$_2$Te$_3$ film grown on Si and STO substrates, respectively. It can be seen that the PISHE current of the 7-QL Bi$_2$Te$_3$ film grown on STO substrate also show three times sign flip when the light spot is moving from the left to the right side of the two contacts, indicating that the PISHE current consists of the superposition of the signal of the top and bottom surface states. One can also note that the PISHE current in the 7-QL Bi$_2$Te$_3$ film grown on Si substrate is more than two orders larger than that grown on STO substrate. To find out the reason, we measure the photoconducivity current of these two samples, i.e., measuring the photocurrent when the samples are under a direct-current (DC) bias. Under a DC bias of 100 mV and an illumination of 1064 nm light of 50 mW, the photoconductivity currents of the 7-QL Bi$_2$Te$_3$ film grown on Si and STO substrates are 10.5 and 0.004 $\mu$A, respectively. It can be seen that the photoconductivity current of the 7-QL Bi$_2$Te$_3$ film grown on Si is more than three orders larger than that grown on STO substrate. This phenomenon indicates that the absorption coefficient of the 7-QL Bi$_2$Te$_3$ film grown on Si is much larger than that on STO substrate, and thus results in much larger PISHE current in the Bi$_2$Te$_3$ film grown on Si substrates.
4. Conclusion
In conclusion, we have investigated the PISHE current in 3D TI Bi$_2$Te$_3$ thin films with different thicknesses grown on Si and STO substrates. The sign of the PISHE current as a function of light spot positions only show one flip in the 3- and 20-QL samples, which is due to the severe oxidation of the top surface states in these samples, as confirmed by the XPS analysis. The sign of the PISHE current flips three times as the light spot is moving from the left to the right side of the two contacts in the 5-, 7- and 12-QL samples, which is due to the superposition of the PSIHE signal of the top and bottom surface states. The impact of the bulk states on the PISHE current has been obtained. The PISHE current contributed by the top and bottom surface states has been successfully separated by fitting a theoretical model to the experimental data. The light power dependence of the PISHE current have also been investigated, and the results are all well fitted by the theoretical model. The PISHE current almost does not change with temperature in the range of 300 to 130 K, confirming that the PSIHE current originates from the surface states. Finally, it is revealed that the PISHE current of the Bi$_2$Te$_3$ thin films grown on Si substrate is more than two orders larger than that grown on STO substrates, which is due to the larger absorption coefficient for Bi$_2$Te$_3$/Si samples. Our results demonstrate that the PISHE current in the Bi$_2$Te$_3$ film of 3 QL is as large as 140 nA/W, which is more than one order larger than that reported in GaAs/AlGaAs and GaN/AlGaN heterojunctions, suggesting that the 3D TI Bi$_2$Te$_3$ films may provide a good platform for spintronic devices with high spin-to-charge conversion efficiency.
Funding
National Natural Science Foundation of China (62074036, 61674038, 11574302); Foreign Cooperation Project of Fujian Province (2019I0005); Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics (KF202108); National Key Research and Development Program of China (2016YFB0402303).
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. O. Mosendz, V. Vlaminck, J. E. Pearson, F. Y. Fradin, G. E. W. Bauer, S. D. Bader, and A. Hoffmann, “Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers,” Phys. Rev. B 82(21), 214403 (2010). [CrossRef]
2. S. Y. Liu, N. J. M. Horing, and X. L. Lei, “Inverse spin Hall effect by spin injection,” Appl. Phys. Lett. 91(12), 122508 (2007). [CrossRef]
3. Y. K. Kato, R. C. Myers, A. C. Gossard, and D. D. Awschalom, “Observation of the spin hall effect in semiconductors,” Science 306(5703), 1910–1913 (2004). [CrossRef]
4. S. Murakami, N. Nagaosa, and S. C. Zhang, “Dissipationless quantum spin current at room temperature,” Science 301(5638), 1348–1351 (2003). [CrossRef]
5. J. L. Yu, Y. H. Chen, Y. Liu, C. Y. Jiang, H. Ma, L. P. Zhu, and X. D. Qin, “Intrinsic photoinduced anomalous Hall effect in insulating GaAs/AlGaAs quantum wells at room temperature,” Appl. Phys. Lett. 102(20), 202408 (2013). [CrossRef]
6. E. Saitoh, M. Ueda, H. Miyajima, and G. Tatara, “Conversion of spin current into charge current at room temperature: Inverse spin-Hall effect,” Appl. Phys. Lett. 88(18), 182509 (2006). [CrossRef]
7. P. Laczkowski, Y. Fu, H. Yang, J. C. Rojas-Sanchez, P. Noel, V. T. Pham, G. Zahnd, C. Deranlot, S. Collin, C. Bouard, P. Warin, V. Maurel, M. Chshiev, A. Marty, J. P. Attane, A. Fert, H. Jaffres, L. Vila, and J. M. George, “Large enhancement of the spin Hall effect in Au by side-jump scattering on Ta impurities,” Phys. Rev. B 96(14), 140405 (2017). [CrossRef]
8. J. C. Lee, L. W. Huang, D. S. Hung, T. H. Chiang, J. C. A. Huang, J. Z. Liang, and S. F. Lee, “Inverse spin hall effect induced by spin pumping into semiconducting ZnO,” Appl. Phys. Lett. 104(5), 052401 (2014). [CrossRef]
9. K. Ando and E. Saitoh, “Observation of the inverse spin Hall effect in silicon,” Nat. Commun. 3(1), 629 (2012). [CrossRef]
10. X. W. He, B. Shen, Y. H. Chen, Q. Zhang, K. Han, C. M. Yin, N. Tang, F. J. Xu, C. G. Tang, Z. J. Yang, Z. X. Qin, G. Y. Zhang, and Z. G. Wang, “Anomalous photogalvanic effect of circularly polarized light incident on the two-dimensional electron gas in AlxGa1−xN/GaN heterostructures at room temperature,” Phys. Rev. Lett. 101(14), 147402 (2008). [CrossRef]
11. J. Yu, X. L. Zeng, Y. M. Wang, L. J. Xia, S. Y. Cheng, Y. Chen, Y. Liu, Y. F. Lai, and Q. Zheng, “Observation of extrinsic photo-induced inverse spin Hall effect in a GaAs/AlGaAs two-dimensional electron gas,” Nanoscale Res. Lett. 13(1), 320 (2018). [CrossRef]
12. F. Bottegoni, C. Zucchetti, M. Finazzi, G. Isella, and F. Ciccacci, “Pure spin currents in Ge probed by inverse spin-Hall effect,” AIP Adv. 7(5), 055907 (2017). [CrossRef]
13. K. Ando, M. Morikawa, T. Trypiniotis, Y. Fujikawa, C. H. W. Barnes, and E. Saitoh, “Direct conversion of light-polarization information into electric voltage using photoinduced inverse spin-Hall effect in Pt/GaAs hybrid structure: Spin photodetector,” J. Appl. Phys. 107(11), 113902 (2010). [CrossRef]
14. P. Mudi, S. K. Khamari, and T. K. Sharma, “Theoretical prediction and experimental demonstration of inter-valley scattering induced inverse spin Hall effect for hot electrons in GaAs,” J. Appl. Phys. 126(6), 065703 (2019). [CrossRef]
15. P. Deorani, J. Son, K. Banerjee, N. Koirala, M. Brahlek, S. Oh, and H. Yang, “Observation of inverse spin Hall effect in bismuth selenide,” Phys. Rev. B 90(9), 094403 (2014). [CrossRef]
16. M. Jamali, J. S. Lee, J. S. Jeong, F. Mahfouzi, Y. Lv, Z. Zhao, B. K. Nikolic, K. A. Mkhoyan, N. Samarth, and J.-P. Wang, “Giant spin pumping and inverse spin Hall effect in the presence of surface and bulk spin-orbit coupling of topological insulator Bi2Se3,” Nano Lett. 15(10), 7126–7132 (2015). [CrossRef]
17. B. B. Singh, S. K. Jena, M. Samanta, K. Biswas, and S. Bedanta, “High spin to charge conversion efficiency in electron beam-evaporated topological insulator Bi2Se3,” ACS Appl. Mater. Interfaces 12(47), 53409–53415 (2020). [CrossRef]
18. C. N. Wu, Y. H. Lin, Y. T. Fanchiang, H. Y. Hung, H. Y. Lin, P. H. Lin, J. G. Lin, S. F. Lee, M. Hong, and J. Kwo, “Strongly enhanced spin current in topological insulator/ferromagnetic metal heterostructures by spin pumping,” J. Appl. Phys. 117(17), 17D148 (2015). [CrossRef]
19. J. Yu, X. Zeng, L. Zhang, K. He, and Q. K. Xue, “Photoinduced inverse spin Hall effect of surface states in the topological insulator Bi2Se3,” Nano Lett. 17(12), 7878–7885 (2017). [CrossRef]
20. B. B. Singh, S. K. Jena, M. Samanta, K. Biswas, B. Satpati, and S. Bedanta, “Inverse spin Hall effect in electron beam evaporated topological insulator Bi2Se3 thin film,” Phys. Status Solidi RRL 13(3), 1800492 (2019). [CrossRef]
21. F. H. Mei, N. Tang, X. Q. Wang, J. X. Duan, S. Zhang, Y. H. Chen, W. K. Ge, and B. Shen, “Detection of spin-orbit coupling of surface electron layer via reciprocal spin Hall effect in InN films,” Appl. Phys. Lett. 101(13), 132404 (2012). [CrossRef]
22. X. Y. Peng, Q. Zhang, B. Shen, J. R. Shi, C. M. Yin, X. W. He, F. J. Xu, X. Q. Wang, N. Tang, C. Y. Jiang, Y. H. Chen, and K. Chang, “Anomalous linear photogalvanic effect observed in a GaN-based two-dimensional electron gas,” Phys. Rev. B 84(7), 075341 (2011). [CrossRef]
23. J. Yu, X. Zeng, L. Zhang, C. Yin, Y. Chen, Y. Liu, S. Cheng, Y. Lai, K. He, and Q. Xue, “Inverse spin Hall effect induced by linearly polarized light in the topological insulator Bi2Se3,” Opt. Express 26(4), 4832–4841 (2018). [CrossRef]
24. S.-Q. Shen, “Spin transverse force on spin current in an electric field,” Phys. Rev. Lett. 95(18), 187203 (2005). [CrossRef]
25. M. C. Wang, S. Qiao, Z. Jiang, S. N. Luo, and J. Qi, “Unraveling photoinduced spin dynamics in the topological insulator Bi2Se3,” Phys. Rev. Lett. 116(3), 036601 (2016). [CrossRef]
