ORCID Profile
0000-0003-0117-8225
Current Organisations
University of Science and Technology of China
,
University of New South Wales
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Optical Physics | Photonics, Optoelectronics and Optical Communications | Condensed Matter Characterisation Technique Development |
Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Technology
Publisher: Optica Publishing Group
Date: 20-04-2022
DOI: 10.1364/OE.456150
Abstract: The photoinduced inverse spin Hall effect (PISHE) has been studied in three dimensional (3D) topological insulator (TI) Bi 2 Te 3 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 Bi 2 Te 3 films, but it flips three times in the 5-, 7- and 12-QL s les. The three-times sign flip is due to the superposition of the PISHE current of the top and bottom surface states in Bi 2 Te 3 films. By analyzing the x-ray photoelectron spectroscopy (XPS) of the Bi 2 Te 3 films, we find that the top surface of the 3- and 20-QL Bi 2 Te 3 films are severely oxidized, leading to only one sign flip in the PISHE. The PISHE contributed by the top and bottom surface states in Bi 2 Te 3 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 Bi 2 Te 3 films grown on Si substrate is more than two orders larger than that grown on SrTiO 3 substrates, which can be attributed to the larger absorption coefficient for Bi 2 Te 3 /Si s les. It is revealed that the PISHE current in 3D TI Bi 2 Te 3 is as large as 140 nA/W in the 3-QL Bi 2 Te 3 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.
Publisher: OSA
Date: 2015
Publisher: AIP Publishing
Date: 06-04-2020
DOI: 10.1063/1.5145359
Abstract: Topological insulators (TIs) are considered as ideal spintronic materials due to the spin-momentum-locked Dirac surface states. The photoinduced anomalous Hall effect (PAHE) is a powerful tool to investigate the spin Hall effect of topological insulators even at room temperature. In this Letter, the PAHE has been observed in three dimensional topological insulator Bi2Te3 thin films grown on Si substrates at room temperature. As the thickness of the Bi2Te3 films increases from 3 to 20 quintuple layer (QL), the PAHE first increases and then decreases, and it reaches a maximum at 7 QL. The sign reversal of the PAHE of the 3 QL s le after oxidation reveals that the PAHE of the Bi2Te3 thin films is dominated by the top surface states, which is further confirmed by the circular photogalvanic effect under front and back illuminations. The photoinduced anomalous Hall conductivity excited by 1064 nm light is as large as 5.28 nA V−1 W−1 cm2 in the 7 QL s le, much larger than that observed in InGaAs/AlGaAs quantum wells (0.445 nA V−1 W−1 cm2) and GaN/AlGaN heterostructures (0.143 nA V−1 W−1 cm2). By comparing the PAHE current excited by 1064 nm with that excited by 1342 nm, we reveal that the tremendous PAHE excited by 1064 nm light is due to the modulation effect of spin injection from Si substrates. The giant PAHE value observed in TI Bi2Te3 may offer spintronic applications of TIs such as high-efficient light-polarization-state detectors.
Publisher: American Chemical Society (ACS)
Date: 28-06-2019
DOI: 10.1021/ACS.NANOLETT.9B01281
Abstract: Continued scaling of semiconductor devices has driven information technology into vastly erse applications. The performance of ultrascaled transistors is strongly influenced by local electric field and strain. As the size of these devices approaches fundamental limits, it is imperative to develop characterization techniques with nanometer resolution and three-dimensional (3D) mapping capabilities for device optimization. Here, we report on the use of single erbium (Er) ions as atomic probes for the electric field and strain in a silicon ultrascaled transistor. Stark shifts on the Er
Publisher: American Physical Society (APS)
Date: 07-04-2021
Publisher: American Physical Society (APS)
Date: 17-08-2011
Publisher: American Chemical Society (ACS)
Date: 29-04-2013
DOI: 10.1021/NL400153P
Abstract: Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.
Publisher: AIP Publishing
Date: 11-2010
DOI: 10.1063/1.3511768
Abstract: The spin splitting in GaN-based heterostructures has been investigated by means of circular photogalvanic effect experiments under uniaxial strain. The ratios of Rashba and Dresselhaus spin-orbit coupling coefficients (R/D ratios) have been measured in AlxGa1−xN/GaN heterostructures with various Al compositions. It is found that the R/D ratio increases from 4.1 to 19.8 with the Al composition of the AlxGa1−xN barrier varied from 15% to 36%. The Dresselhaus coefficient of bulk GaN is experimentally obtained to be 0.4 eV Å3. The results indicate that the spin splitting in GaN-based heterostructures can be modulated effectively by the polarization-induced electric fields.
Publisher: American Physical Society (APS)
Date: 27-06-2022
Publisher: AIP Publishing
Date: 12-03-2021
DOI: 10.1063/5.0045473
Abstract: Ultra-thin Bi2Se3 nanoplates with high crystal quality are obtained by chemical vapor deposition (CVD). A giant circular photogalvanic effect (CPGE) has been observed in the ultra-thin Bi2Se3 nanoplates, which is about one order larger than that previously observed in the thick Bi2Se3 nanoplates grown by CVD and that in the thin Bi2Se3 film grown by molecular beam epitaxy. By applying an ionic liquid gate, the CPGE can be effectively tuned. As the gate voltage increases, the magnitude of the CPGE current decreases, suggesting that the CPGE current under zero gate voltage is dominated by surface states rather than the two-dimensional electron gas (2DEG). It is revealed that as the surface roughness of the Bi2Se3 nanoplates increases, the CPGE decreases and finally reverses the sign, indicating the dominant contribution of the CPGE switches from the top surface states to the 2DEG or the bottom surface states.
Publisher: American Physical Society (APS)
Date: 27-07-2021
Publisher: Springer Science and Business Media LLC
Date: 05-2013
DOI: 10.1038/NATURE12081
Abstract: The detection of electron spins associated with single defects in solids is a critical operation for a range of quantum information and measurement applications under development. So far, it has been accomplished for only two defect centres in crystalline solids: phosphorus dopants in silicon, for which electrical read-out based on a single-electron transistor is used, and nitrogen-vacancy centres in diamond, for which optical read-out is used. A spin read-out fidelity of about 90 per cent has been demonstrated with both electrical read-out and optical read-out however, the thermal limitations of the former and the poor photon collection efficiency of the latter make it difficult to achieve the higher fidelities required for quantum information applications. Here we demonstrate a hybrid approach in which optical excitation is used to change the charge state (conditional on its spin state) of an erbium defect centre in a silicon-based single-electron transistor, and this change is then detected electrically. The high spectral resolution of the optical frequency-addressing step overcomes the thermal broadening limitation of the previous electrical read-out scheme, and the charge-sensing step avoids the difficulties of efficient photon collection. This approach could lead to new architectures for quantum information processing devices and could drastically increase the range of defect centres that can be exploited. Furthermore, the efficient electrical detection of the optical excitation of single sites in silicon represents a significant step towards developing interconnects between optical-based quantum computing and silicon technologies.
Publisher: American Chemical Society (ACS)
Date: 17-11-2017
DOI: 10.1021/ACS.NANOLETT.7B04172
Abstract: The three-dimensional (3D) topological insulator (TI) Bi
Publisher: The Optical Society
Date: 15-02-2018
DOI: 10.1364/OE.26.004832
Publisher: American Physical Society (APS)
Date: 12-01-2023
Publisher: IOP Publishing
Date: 19-07-2019
Publisher: AIP Publishing
Date: 20-07-2009
DOI: 10.1063/1.3186042
Abstract: We report an effective and nondestructive method based on circular photogalvanic effect (CPGE) to detect the lattice polarity of InN. Because of the lattice inversion between In- and N-polar InN, the energy band spin splitting is opposite for InN films with different polarities. Consequently under light irradiation with the same helicity, CPGE photocurrents in In- and N-polar layers will have opposite directions, thus the polarity can be detected. This method is demonstrated by our CPGE measurements in both n- and p-type InN films.
Publisher: American Physical Society (APS)
Date: 03-10-2008
Publisher: AIP Publishing
Date: 07-02-2022
DOI: 10.1063/5.0080033
Abstract: Strain is a useful method to manipulate properties of three-dimensional (3D) topological insulators (TIs). In this study, we demonstrate the possibility to tune the circular photogalvanic effect (CPGE) of surface states of 3D TI Sb2Te3 films by applying external strain. The CPGE of 3D TI Sb2Te3 grown on SrTiO3 (STO) with different thicknesses has been systematically investigated. It is found that as the thickness of Sb2Te3 films increases from 7-quintuple layer (QL) to 27-QL, the CPGE current first increases and then decreases. Additionally, the CPGE currents demonstrate remarkable temperature dependence, which even reverse sign when the temperature is increased from 77 to 300 K. This phenomenon is due to the vertical thermoelectric effect and inverse spin Hall effect. Finally, the CPGE measurements of Sb2Te3 films under different mechanical strains are performed, and it is found that the CPGE current linearly decreases with the increase in the external strain. The variation in the CPGE current can be tuned up to 11% and 44% in the 18- and 12-QL Sb2Te3 grown on STO substrates under a tensile strain of 0.0225 and 0.0066, respectively. In particular, it can even reach 100% in the 30-QL Sb2Te3 film grown on an InP substrate under a tensile strain of 0.0033, which is due to the combined effect of mechanical deformation and spin injection from substrates. Our work provides a method to effectively manipulate the CPGE in 3D TIs by the combined effect of mechanical strain and spin injection from substrates, which paves the way for novel opto-spintronic devices.
Publisher: American Physical Society (APS)
Date: 05-12-2019
Publisher: Oxford University Press (OUP)
Date: 09-05-2023
DOI: 10.1093/NSR/NWAD134
Abstract: Efficient detection of single optical centres in solids is essential for quantum information processing, sensing, and single-photon generation applications. In this work, we use radio-frequency (RF) reflectometry to electrically detect the photoionisation induced by a single Er3 + ion in Si. The high bandwidth and sensitivity of the RF reflectometry provide sub-100-ns time resolution for the photoionisation detection. With this technique, the optically excited state lifetime of a single Er3 + ion in a Si nano-transistor is measured for the first time to be 0.49 ± 0.04μs. Our results demonstrate an efficient approach for detecting a charge state change induced by Er excitation and relaxation. This approach could be used for fast readout of other single optical centres in solids and is attractive for large-scale integrated optical quantum systems thanks to the multi-channel RF reflectometry demonstrated with frequency multiplexing techniques.
Publisher: Springer Science and Business Media LLC
Date: 04-02-2009
Publisher: American Chemical Society (ACS)
Date: 26-03-2020
Publisher: IEEE
Date: 12-2012
Publisher: American Chemical Society (ACS)
Date: 03-01-2022
DOI: 10.1021/ACS.NANOLETT.1C04072
Abstract: The detection of charge trap ionization induced by resonant excitation enables spectroscopy on single Er
Publisher: American Physical Society (APS)
Date: 08-12-2015
Publisher: American Physical Society (APS)
Date: 23-10-2020
Publisher: AIP Publishing
Date: 21-03-2011
DOI: 10.1063/1.3569948
Abstract: The photocurrent has been measured in Al0.25Ga0.75N/GaN heterostructures at room temperature, and the photoinduced anomalous Hall effect (AHE) was observed. The AHE current changes linearly with the varied longitudinal electric fields. Due to the strong Rashba spin–orbit coupling of the two-dimensional electron gas in Al0.25Ga0.75N/GaN heterostructures, the intrinsic anomalous Hall mechanism is supposed to contribute to the photoinduced AHE. The photoinduced AHE measurement proposed in this study could be used to other spin related measurements at room temperature.
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3666571
Publisher: IOP Publishing
Date: 09-03-2022
Abstract: In idual optical emitters coupled via coherent interactions are attractive qubits for quantum communications applications. Here, we present the first study of single pairs of interacting rare earth ions and determine the interactions between ions in the pair with high resolution. We identify two ex les of Er 3+ pair sites in Er implanted Si and characterise the interactions using optical Zeeman spectroscopy. We identify one pair as two Er 3+ ions in sites of at least C 2 symmetry coupled via a large, 200 GHz, Ising-like spin interaction in both optical ground and excited states. The high measurement resolution allows non-Ising contributions to the interaction of <?CDATA $ 1 % to be observed, attributed to site distortion. By bringing two optical transitions into resonance with a magnetic field, we observe a 0.8 GHz optical interaction of unusual magnetic-dipole/electric-dipole character with strong polarization selection rules. We discuss the use of this type of strongly coupled, field-tunable rare earth pair system for quantum processing.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2021
DOI: 10.1038/S41467-021-21781-5
Abstract: High fidelity single-shot readout of qubits is a crucial component for fault-tolerant quantum computing and scalable quantum networks. In recent years, the nitrogen-vacancy (NV) center in diamond has risen as a leading platform for the above applications. The current single-shot readout of the NV electron spin relies on resonance fluorescence method at cryogenic temperature. However, the spin-flip process interrupts the optical cycling transition, therefore, limits the readout fidelity. Here, we introduce a spin-to-charge conversion method assisted by near-infrared (NIR) light to suppress the spin-flip error. This method leverages high spin-selectivity of cryogenic resonance excitation and flexibility of photoionization. We achieve an overall fidelity 95% for the single-shot readout of an NV center electron spin in the presence of high strain and fast spin-flip process. With further improvements, this technique has the potential to achieve spin readout fidelity exceeding the fault-tolerant threshold, and may also find applications on integrated optoelectronic devices.
Publisher: AIP Publishing
Date: 26-07-2010
DOI: 10.1063/1.3467835
Abstract: We report a strong circular photogalvanic effect (CPGE) in ZnO epitaxial films under interband excitation. It is observed that CPGE current is as large as 100 nA/W in ZnO, which is about one order in magnitude higher than that in InN film while the CPGE currents in GaN films are not detectable. The possible reasons for the above observations are the strong spin orbit coupling in ZnO or the inversed valence band structure of ZnO.
Publisher: American Chemical Society (ACS)
Date: 28-01-2022
Publisher: American Physical Society (APS)
Date: 08-09-2022
Publisher: Elsevier BV
Date: 09-2022
Publisher: AIP Publishing
Date: 13-08-2007
DOI: 10.1063/1.2768918
Abstract: The circular photogalvanic effect (CPGE) of the two-dimensional electron gas (2DEG) in Al0.25Ga0.75N∕GaN heterostructures induced by infrared radiation has been investigated under uniaxial strain. The observed photocurrent consists of the superposition of the CPGE and the linear photogalvanic effect currents, both of which are up to 10−2nA. The litude of the CPGE current increases linearly with additional strain and is enhanced by 18.6% with a strain of 2.2×10−3. Based on the experimental results, the contribution of bulk-inversion asymmetry (BIA) and structure-inversion asymmetry (SIA) spin splitting of the 2DEG to the CPGE current in the heterostructures is separated, and the ratio of SIA and BIA terms is estimated to be about 13.2, indicating that the SIA is the dominant mechanism to induce the k-linear spin splitting of the subbands in the triangular quantum well at AlxGa1−xN∕GaN heterointerfaces.
Start Date: 2015
End Date: 12-2018
Amount: $373,536.00
Funder: Australian Research Council
View Funded Activity