Dirac材料光驱动异质结中的谷区热电子学
Valley caloritronics in a photodriven hetero-junction of Dirac materials
摘要：
我们考虑一个横向异质结，其中左和右引线由单层石墨烯制成，中间区域由用非共振圆偏振辐射照射的带间隙的倾斜狄拉克材料（硼氢化物或醌型石墨烯）制成。倾斜参数$v_t$使得带隙间接地并且与没有倾斜的狄拉克材料相比在量值上更小。暴露于辐射使得中心区域的带隙谷依赖性，其显示其签名为谷极化电荷和热流，从而引起谷塞贝克效应。我们研究了这种结的谷极化电导、热导、热电势和优值随化学势$μ$和可调带隙参数$η$的变化。对于非零的$η$，所有的谷极化量在化学势的某个值处达到峰值，然后渐近地消失。间隙参数的增加增强了谷热电势和谷品质因数，而谷电导（电和热）与$η$表现出非单调行为。我们还比较了谷极化量与其相应的电荷对应物（有效的贡献，从两个山谷）。电荷热电势和电荷优值与$η$表现为非单调性，电荷电导（电和热）与$η$表现为下降趋势。此外，倾斜参数降低了载流子通过结的有效传输，从而减少了所有的电荷和谷极化量。由于色散中的间隙可以通过改变光的强度以及Semenoff质量来调节，因此该结关于其热电性质的可调谐性可以通过实验实现。
英文摘要：
We consider a lateral hetero-junction where the left and right leads are made of monolayer graphene and the middle region is made of a gapped tilted Dirac material (borophene or quinoid graphene) illuminated with off-resonant circularly polarized radiation. The tilt parameter $v_t$ makes the band gap indirect and smaller in magnitude as compared to Dirac materials without tilt. Exposure to radiation makes the band gaps of the central region valley-dependent which show their signatures as valley polarized charge and thermal currents, thereby causing a valley Seebeck effect. We study the variation of the valley polarized electrical conductance, thermal conductance, thermopower and figure of merit of this junction with chemical potential $μ$ and a tunable gap parameter $η$. For non-zero $η$, all the valley polarized quantities are peaked at certain values of chemical potential and then vanish asymptotically. Increase in gap parameter enhances the valley thermopower and valley figure of merit, whereas the valley conductances (electrical and thermal) show non monotonic behavior with $η$. We also compare the valley polarized quantities with their corresponding charge counterparts (effective contribution from both the valleys). The charge thermopower and the charge figure of merit behave non monotonically with $η$ and the charge conductances (electrical and thermal) depict a decreasing trend with $η$. Furthermore, the tilt parameter reduces the effective transmission of carriers through the junction, thereby diminishing all the charge and valley polarized quantities. As the gaps in the dispersion can be adjusted by varying the intensity of light as well as the Semenoff mass, the tunability of this junction with regard to its thermoelectric properties may be experimentally realizable.
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