Optical and electric control of spin and valley-polarized transport in magnetic WSe2 superlattice
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摘要: 基于磁性WSe2超晶格系统，探讨了非共振圆偏振光与栅极电压及其对隧穿、谷极化及自旋极化的影响；发现了单层WSe2的弹道输运操纵以及基于磁性WSe2的NM/FM/NM结的周期性阵列量子输运的调控．结果表明：通过增加势垒的数量，圆偏振光临界值可消除透射能隙；圆偏振光和栅极电压可视为一个透射阀,也可用于控制自旋和谷极化的敏感旋钮；发现了在WSe2超晶格中的克莱因隧穿是自旋-谷相关的；自旋-谷极化可以利用栅极电压和圆偏振光来调整和转换．Abstract: In this paper, we considered the magnetic WSe2 superlattice system, explored the effects of non-resonant circularly polarized light and gate voltage on tunneling, valley polarization and spin polarization, the manipulation of ballistic transport in single-layer WSe2 and control of the quantum transport in the periodic array of NM/FM/NM junctions based on magnetic WSe2. The results show that the critical value of circularly polarized light can eliminate the transmission energy gap by increasing the number of potential barriers; The circularly polarized light and gate voltage can be regarded as a transmission valve and a sensitive knob for controlling the spin and valley polarization; Klein tunneling in WSe2 super lattice is spin-valley dependent; spin-valley polarization can be adjusted and converted by grid voltage and circularly polarized light.
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Key words:
- magnetic WSe2 /
- superlattice /
- circularly polarized light /
- gate voltage /
- spin transport /
- valley polarized transport
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图 1
$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}={\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}^{\boldsymbol{c}} $ 、$ \boldsymbol{U}=6 $ eV、$ \boldsymbol{h}=0 $ 时的WSe2能带结构注：对于自旋向上的电子，在$ K\mathrm{、}{K}' $谷的$ {\varDelta}_{\omega }^{c} $分别是−0.955 eV和 0.745 eV；对自旋向下的电子，在$ K\mathrm{、}{K}' $谷的$ {\varDelta}_{\omega }^{c} $分别是−0.745 eV 和0.955 eV．
图 2
$ \boldsymbol{N}=1 $ 、$ \boldsymbol{D}=10 $ nm、$ \boldsymbol{L}=20 $ nm、$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}={\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}^{\boldsymbol{c}}=0.745 $ eV、$ \boldsymbol{U}=6 $ eV、$ \boldsymbol{h}=0 $ 时透射率的等高线示意
图 3
$ \boldsymbol{U}=6\mathbf{e}\mathbf{V}\mathbf{、}\boldsymbol{h}=0 $ 、$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}={\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}^{\boldsymbol{c}} $ 时作为费米能量的$ {\boldsymbol{K}}^{\boldsymbol{\text{'}}} $ 谷和入射角函数的透射率等高线图注：左列和右列分别代表$ N=2 $和$ N=6 $ ； a、b、e和f中$ {\varDelta}_{\omega }^{c}=0.745 $eV；c、d、g和h中$ {\varDelta}_{\omega }^{c}=0.955 $ eV．
图 4
$ \boldsymbol{U}=3 $ eV、$ \boldsymbol{h}=0.5 $ eV、$ \boldsymbol{D}=10 $ nm、$ \boldsymbol{L}=5 $ nm、$ \boldsymbol{E}=0.95 $ eV、$ \boldsymbol{N}=2 $ 时作为$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }} $ 函数的不同自旋谷的透射谱
图 5
$ \boldsymbol{U}=3 $ eV、$ \boldsymbol{h}=0.5 $ eV、$ \boldsymbol{D}=10 $ nm、$ \boldsymbol{L}=5 $ nm、$ \boldsymbol{E}=0.95 $ eV、$ \boldsymbol{N}=6 $ 时作为$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }} $ 函数的不同自旋谷的透射谱
图 6
$ \boldsymbol{U}=3 $ eV、$ \boldsymbol{h}=0.5 $ eV、$ \boldsymbol{D}=20 $ nm、$ \boldsymbol{L}=10 $ nm、$ \boldsymbol{E}=0.95 $ eV、$ \boldsymbol{N}=6 $ 时作为$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }} $ 函数的不同自旋谷的透射率
图 7
$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}=0 $ ,$ \boldsymbol{h}=0.5 $ eV，$ \boldsymbol{D}=20 $ nm，$ \boldsymbol{L}=10 $ nm，$ \boldsymbol{E}=0.95 $ eV，$ \boldsymbol{N}=2 $ 时，作为$ \boldsymbol{U} $ 函数的不同自旋谷的透射谱注： a～d分别显示了当$ N=2 $和$ 6 $时，在没有非共振光（$ {\varDelta}_{\omega }=0 $）的情况下，所有具有自旋和谷特点的透射几率与$ U $的关系．
图 8
$ {\boldsymbol{\varDelta}}_{\boldsymbol{\omega }}=0 $ 、$ \boldsymbol{h}=0.5 $ eV、$ \boldsymbol{D}=20 $ nm、$ \boldsymbol{L}=10 $ nm、$ \boldsymbol{E}=0.95 $ eV、$ \boldsymbol{N}=6 $ 时作为$ \boldsymbol{U} $ 函数的不同自旋谷的透射谱注：a～d分别显示了当$ N=2 $和$ 6 $时，在没有非共振光（$ {\varDelta}_{\omega }=0 $）的情况下，所有具有自旋和谷特点的透射几率与$ U $的关系．
图 9
$ \boldsymbol{h}=0.5 $ eV、$ \boldsymbol{D}=10 $ nm、$ \boldsymbol{L}=20 $ nm、$ \boldsymbol{E}=0.95 $ eV、$ \boldsymbol{N}=2 $ (左边)、$ \boldsymbol{N}=6 $ (右边)时自旋极化的等高线图
图 10
$ \boldsymbol{h}=0.5 $ eV、$ \boldsymbol{D}=10 $ nm、$ \boldsymbol{L}=20 $ nm、$ \boldsymbol{E}=0.95 $ eV、$ \boldsymbol{N}=2 $ (左边)、$ \boldsymbol{N}=6 $ (右边)时谷极化的等高线图 -
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