深圳大学学报（理工版）
深圳大學學報（理工版）
심수대학학보（리공판）
JOURNAL OF SHENZHEN UNIVERSITY (SCIENCE & ENGINEERING)
2014年
2期
111-118
,共8页
王斌%李健伟%卫亚东%王健
王斌%李健偉%衛亞東%王健
왕빈%리건위%위아동%왕건
凝聚态物理%石墨烯带%正常-超导结%Andreev反射%非平衡格林函数%密度泛函理论
凝聚態物理%石墨烯帶%正常-超導結%Andreev反射%非平衡格林函數%密度汎函理論
응취태물리%석묵희대%정상-초도결%Andreev반사%비평형격림함수%밀도범함이론
condensed matter physics%graphene nanoribbon%normal-superconducting junction%Andreev reflection%non-equilibrium Green’s function ( NEGF)%density functional theory ( DFT)
基于非平衡格林函数( non-equilibrium Green’s function, NEGF )和密度泛函理论( density functional theory, DFT),从第一性原理出发研究Armchair型和Zigzag型的石墨烯带正常-超导结的电子输运性质,计算了缺陷对这两种正常-超导结输运性质的影响。计算表明,对无缺陷正常-超导石墨烯带,在超导能隙内, Andreev反射系数TA恰好等于正常石墨烯带的电子透射系数TN 。当石墨烯带存在缺陷时, Andreev反射系数TA不再是一个常数,而在超导能隙边缘出现两个尖锐的峰,其峰值大于正常系统的电子透射系数。在超导能隙之外, Andreev反射系数TA逐渐减小为0,准粒子的正常隧穿几率T1逐渐增大,且趋于无超导下的正常系统的电子透射系数TN 。不同缺陷构型对石墨烯带中载流子的输运过程影响不同。如果缺陷的存在对正常石墨烯带电子散射过程影响越大,则其对正常-超导体系中的Andreev反射和准粒子散射影响也越大。
基于非平衡格林函數( non-equilibrium Green’s function, NEGF )和密度汎函理論( density functional theory, DFT),從第一性原理齣髮研究Armchair型和Zigzag型的石墨烯帶正常-超導結的電子輸運性質,計算瞭缺陷對這兩種正常-超導結輸運性質的影響。計算錶明,對無缺陷正常-超導石墨烯帶,在超導能隙內, Andreev反射繫數TA恰好等于正常石墨烯帶的電子透射繫數TN 。噹石墨烯帶存在缺陷時, Andreev反射繫數TA不再是一箇常數,而在超導能隙邊緣齣現兩箇尖銳的峰,其峰值大于正常繫統的電子透射繫數。在超導能隙之外, Andreev反射繫數TA逐漸減小為0,準粒子的正常隧穿幾率T1逐漸增大,且趨于無超導下的正常繫統的電子透射繫數TN 。不同缺陷構型對石墨烯帶中載流子的輸運過程影響不同。如果缺陷的存在對正常石墨烯帶電子散射過程影響越大,則其對正常-超導體繫中的Andreev反射和準粒子散射影響也越大。
기우비평형격림함수( non-equilibrium Green’s function, NEGF )화밀도범함이론( density functional theory, DFT),종제일성원리출발연구Armchair형화Zigzag형적석묵희대정상-초도결적전자수운성질,계산료결함대저량충정상-초도결수운성질적영향。계산표명,대무결함정상-초도석묵희대,재초도능극내, Andreev반사계수TA흡호등우정상석묵희대적전자투사계수TN 。당석묵희대존재결함시, Andreev반사계수TA불재시일개상수,이재초도능극변연출현량개첨예적봉,기봉치대우정상계통적전자투사계수。재초도능극지외, Andreev반사계수TA축점감소위0,준입자적정상수천궤솔T1축점증대,차추우무초도하적정상계통적전자투사계수TN 。불동결함구형대석묵희대중재류자적수운과정영향불동。여과결함적존재대정상석묵희대전자산사과정영향월대,칙기대정상-초도체계중적Andreev반사화준입자산사영향야월대。
The first principles calculation has been carried out to investigate the quantum transport properties of normal-superconducting graphene nanoribbons ( GNRs) within the combination of non-equilibrium Green’s function ( NEGF) and density functional theory ( DFT) . The Andreev reflection coefficient TA and quasi-particle transmission probability T1 of normal-superconducting system of a series of defective configurations were investigated in detail. As a comparison, the electric transmission coefficient TN of normal system was also calculated. In the pristine graphene nanoribbons, The Andreev reflection coefficient TA is a constant and exactly equals to electric transmission coefficient TN of the normal system in the superconducting energy gap, which indicates that the Andreev conductance is twice of the normal electric conductance. In the defective configurations of graphene nanoribbons, TA shows two sharp peaks at E =± Δ, and the peak values are larger than the electric conductance of normal system. Outside the superconducting energy gap, Andreev conductance decays to zero, and quasi-particle transmission probability increases to the normal electric transmission coefficient gradually. Different defective configurations give different influence to the Andreev reflection of the normal-superconducting graphene nanoribbons.
