Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle...Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.展开更多
The heating and helicity effects induced by circularly polarized laser excitation are entangled in the helicity-dependent all-optical switching(HD-AOS),which hinders understanding the magnetization dynamics involved.H...The heating and helicity effects induced by circularly polarized laser excitation are entangled in the helicity-dependent all-optical switching(HD-AOS),which hinders understanding the magnetization dynamics involved.Here,applying a dual-pump laser excitation,first with a linearly polarized(LP) laser pulse followed by a circularly polarized(CP) laser pulse,the timescales and contribution from heating and helicity effects in HD-AOS were identified with a Pt/Co/Pt triple-layer.When the LP laser pulses preheat the sample to a nearly fully demagnetized state,the CP laser pulses with a power reduced by 80% switch the sample’s magnetization.By varying the time delay between the two pump pulses,the results show that the helicity effect,which gives rise to the deterministic helicity-induced switching,arises almost instantly within 200 fs close to the pulse width upon laser excitation.The results reveal that the transient magnetization state upon which CP laser pulses impinge is the key factor for achieving HD-AOS,and importantly,the tunability between heating and helicity effects with the unique dualpump laser excitation approach will enable HD-AOS in a wide range of magnetic material systems having wideranging implications for potential ultrafast spintronics applications.展开更多
The helicity-dependent photoconductance of the edge states in three-dimensional topological insulator Bi_(2)Te_(3)films is investigated.It is revealed that the helicity-dependent photoconductivity current on the left ...The helicity-dependent photoconductance of the edge states in three-dimensional topological insulator Bi_(2)Te_(3)films is investigated.It is revealed that the helicity-dependent photoconductivity current on the left edge of the Bi_(2)Te_(3)film shows an opposite sign with that on the right edge.In addition,the helicity-dependent photoconductivity current increases linearly with the applied longitudinal electric field,and it reverses the sign with the reversal of the electric field.As the thickness of the Bi_(2)Te_(3)film increases,the helicity-dependent photoconductivity current also increases.Theoretical analysis suggests that the helicity-dependent photo-conductivity current may come from the intrinsic spin orbit coupling(SOC)or the SOC introduced by the chiral impurities or defects.展开更多
By numerically solving the three-dimensional time-dependent Schrödinger equation,we have investigated multiphoton ionization of hydrogen atom in the two-color circularly polarized(TCCP)laser fields consisting of ...By numerically solving the three-dimensional time-dependent Schrödinger equation,we have investigated multiphoton ionization of hydrogen atom in the two-color circularly polarized(TCCP)laser fields consisting of a strong 400 nm and a much weaker 800 nm pulses.Due to the presence of perturbative 800 nm laser pulse,sideband peaks emerge between the above-threshold ionization rings in the photoelectron momentum distributions.Our numerical results show that the sideband peaks exhibit one-lobe structure in the co-rotating TCCP laser fields,while it displays the three-lobe structure in the counter-rotating TCCP laser fields.Moreover,the photoelectron yield of sidebands in the co-rotating TCCP fields is much higher than those of the counter-rotating TCCP fields.These phenomena could be well explained from the perspective of the photon-absorption channels via the selection rules.Interestingly,an obvious phase shift between the sidebands of different orders from the co-rotating and counter-rotating TCCP fields is observed.This shift indicates the helicity-dependent time delay in the one-photon continuum-continuum transition process.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62074036,61674038,and 11574302)the Foreign Cooperation Project of Fujian Province,China(Grant No.2023I0005)+2 种基金the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(Grant No.KF202108)the National Key Research and Development Program of China(Grant No.2016YFB0402303)the Foundation of Fujian Provincial Department of Industry and Information Technology of China(Grant No.82318075)。
文摘Helicity-dependent photocurrent(HDPC)of the surface states in a high-quality topological insulator(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate grown by chemical vapor deposition(CVD)is investigated.By investigating the angle-dependent HDPC,it is found that the HDPC is mainly contributed by the circular photogalvanic effect(CPGE)current when the incident plane is perpendicular to the connection of the two contacts,whereas the circular photon drag effect(CPDE)dominates the HDPC when the incident plane is parallel to the connection of the two contacts.In addition,the CPGE of the(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplate is regulated by temperature,light power,excitation wavelength,the source–drain and ionic liquid top-gate voltages,and the regulation mechanisms are discussed.It is demonstrated that(Bi_(0.7)Sb_(0.3))_(2)Te_(3)nanoplates may provide a good platform for novel opto-spintronics devices.
基金financially supported by the National Key Research and Development Program of China (No. 2016YFA0300803)the National Natural Science Foundation of China (Nos.61427812 and 11774160)+4 种基金the Natural ScienceFoundation of Jiangsu Province of China (No.BK20192006)support of National Key R&D Program of China (No.2021YFB3601600)the Natural Science Foundation of Jiangsu Province of China (No.BK20200307)support of the UK EPSRC (No.EP/T027916/1)supported by the EPSRC TER AS WITCH project (project ID EP/T027916/1)。
文摘The heating and helicity effects induced by circularly polarized laser excitation are entangled in the helicity-dependent all-optical switching(HD-AOS),which hinders understanding the magnetization dynamics involved.Here,applying a dual-pump laser excitation,first with a linearly polarized(LP) laser pulse followed by a circularly polarized(CP) laser pulse,the timescales and contribution from heating and helicity effects in HD-AOS were identified with a Pt/Co/Pt triple-layer.When the LP laser pulses preheat the sample to a nearly fully demagnetized state,the CP laser pulses with a power reduced by 80% switch the sample’s magnetization.By varying the time delay between the two pump pulses,the results show that the helicity effect,which gives rise to the deterministic helicity-induced switching,arises almost instantly within 200 fs close to the pulse width upon laser excitation.The results reveal that the transient magnetization state upon which CP laser pulses impinge is the key factor for achieving HD-AOS,and importantly,the tunability between heating and helicity effects with the unique dualpump laser excitation approach will enable HD-AOS in a wide range of magnetic material systems having wideranging implications for potential ultrafast spintronics applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62074036 and 61674038)the National Key Research and Development Program of China(Grant No.2016YFB0402303)。
文摘The helicity-dependent photoconductance of the edge states in three-dimensional topological insulator Bi_(2)Te_(3)films is investigated.It is revealed that the helicity-dependent photoconductivity current on the left edge of the Bi_(2)Te_(3)film shows an opposite sign with that on the right edge.In addition,the helicity-dependent photoconductivity current increases linearly with the applied longitudinal electric field,and it reverses the sign with the reversal of the electric field.As the thickness of the Bi_(2)Te_(3)film increases,the helicity-dependent photoconductivity current also increases.Theoretical analysis suggests that the helicity-dependent photo-conductivity current may come from the intrinsic spin orbit coupling(SOC)or the SOC introduced by the chiral impurities or defects.
基金This work was supported by the National Key Research and Development Program of China(Grants No.2019YFA0308300)the National Natural Science Foundation of China(Grant Nos.11874163 and 12021004).
文摘By numerically solving the three-dimensional time-dependent Schrödinger equation,we have investigated multiphoton ionization of hydrogen atom in the two-color circularly polarized(TCCP)laser fields consisting of a strong 400 nm and a much weaker 800 nm pulses.Due to the presence of perturbative 800 nm laser pulse,sideband peaks emerge between the above-threshold ionization rings in the photoelectron momentum distributions.Our numerical results show that the sideband peaks exhibit one-lobe structure in the co-rotating TCCP laser fields,while it displays the three-lobe structure in the counter-rotating TCCP laser fields.Moreover,the photoelectron yield of sidebands in the co-rotating TCCP fields is much higher than those of the counter-rotating TCCP fields.These phenomena could be well explained from the perspective of the photon-absorption channels via the selection rules.Interestingly,an obvious phase shift between the sidebands of different orders from the co-rotating and counter-rotating TCCP fields is observed.This shift indicates the helicity-dependent time delay in the one-photon continuum-continuum transition process.
