With the development of attosecond science, tunneling time can now be measured experimentally with the attoclock technique. However, there are many different theoretical definitions of tunneling time and no consensus ...With the development of attosecond science, tunneling time can now be measured experimentally with the attoclock technique. However, there are many different theoretical definitions of tunneling time and no consensus has been achieved.Here, we bridge the relationship between different definitions of tunneling time based on a quantum travel time in onedimensional rectangular barrier tunneling problem. We find that the real quantum travel time t_(Re) is equal to the Bohmian time t_(Bohmian), which is related to the resonance lifetime of a bound state. The total quantum travel time τt can perfectly retrieve the transversal time t_x and the Büttiker–Landauer time τ_(BL) in two opposite limits, regardless of the particle energy.展开更多
Applying the transfer matrix and Green’s function methods,we study the valley-resolved transport properties of zigzag graphene nanoribbon(ZGN_(R))junctions.The width of the left and right ZGN_(R)s are N_(L)and N_(R),...Applying the transfer matrix and Green’s function methods,we study the valley-resolved transport properties of zigzag graphene nanoribbon(ZGN_(R))junctions.The width of the left and right ZGN_(R)s are N_(L)and N_(R),and N_(L)≥N_(R).The step/dip positions of the conductance G,the intravalley transmission coefficients(TKKand TK’K’),and the valley polarization efficiency PK’K correspond to the subband edges of the right/left ZGN_(R)that are controlled by N_(R)/N_(L).The intervalley transmission coefficients(TKK and TK’K)exhibit peaks at most of the subband edge of the left and right ZGN_(R)s.In the bulk gap of the right ZGN_(R),TKK’=TK’K=0,and PKK’=±1,the valley polarization is well preserved.As N_(R)increases,the energy region for PK’K=±1 decreases.When N_(L)is fixed and N_(R)decreases,G,TKK,TK’K’and PKK’exhibit more and more dips,and the peaks of TKK’(TK’K)become more and more high,especially when(N_(L)-N_(R))/2 is odd.These characters are quite useful for manipulating the valley dependent transport properties of carriers in ZGN_(R)junctions by modulating N_(L)or N_(R),and our results are helpful to the design of valleytronics based on ZGN_(R)junctions.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0401100)the National Natural Science Foundation of China(Grant Nos.11425414,11504215,and 11874246)
文摘With the development of attosecond science, tunneling time can now be measured experimentally with the attoclock technique. However, there are many different theoretical definitions of tunneling time and no consensus has been achieved.Here, we bridge the relationship between different definitions of tunneling time based on a quantum travel time in onedimensional rectangular barrier tunneling problem. We find that the real quantum travel time t_(Re) is equal to the Bohmian time t_(Bohmian), which is related to the resonance lifetime of a bound state. The total quantum travel time τt can perfectly retrieve the transversal time t_x and the Büttiker–Landauer time τ_(BL) in two opposite limits, regardless of the particle energy.
文摘Applying the transfer matrix and Green’s function methods,we study the valley-resolved transport properties of zigzag graphene nanoribbon(ZGN_(R))junctions.The width of the left and right ZGN_(R)s are N_(L)and N_(R),and N_(L)≥N_(R).The step/dip positions of the conductance G,the intravalley transmission coefficients(TKKand TK’K’),and the valley polarization efficiency PK’K correspond to the subband edges of the right/left ZGN_(R)that are controlled by N_(R)/N_(L).The intervalley transmission coefficients(TKK and TK’K)exhibit peaks at most of the subband edge of the left and right ZGN_(R)s.In the bulk gap of the right ZGN_(R),TKK’=TK’K=0,and PKK’=±1,the valley polarization is well preserved.As N_(R)increases,the energy region for PK’K=±1 decreases.When N_(L)is fixed and N_(R)decreases,G,TKK,TK’K’and PKK’exhibit more and more dips,and the peaks of TKK’(TK’K)become more and more high,especially when(N_(L)-N_(R))/2 is odd.These characters are quite useful for manipulating the valley dependent transport properties of carriers in ZGN_(R)junctions by modulating N_(L)or N_(R),and our results are helpful to the design of valleytronics based on ZGN_(R)junctions.
