Moléculas de Andreev mediadas por férmions de Majorana
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Data
2020-03-05
Autores
Sanches, José Eduardo Cardozo
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Estudou-se teoricamente um modelo composto por um fio de Kitaev na fase topológica com dois pontos quânticos (QDs - Quantum Dots), um em cada extremidade do nanofio. Desta forma, dois casos foram factíveis de análise, um deles com os estados ligados de Majorana (MBSs - Majorana Bound States) das bordas do fio acoplados a um único QD e o segundo em que se tem ambos os MBSs acoplados aos dois QDs. Para a primeira situação três condições foram estudadas, nas quais se verificou, na primeira, os perfis de férmions de Majorana não locais, dados pelo acoplamento entre o MBS e o QD mais próximo e, nas outras duas condições, dois perfis relacionados aos acoplamentos dos dois MBSs a um QD, em que se considerou também a superposição entre os MBS. Estes dois perfis são denominados de bowtie e diamond, já conhecidos na literatura, possuindo também experimentos que validam suas manifestações. No segundo caso, em que se tem o acoplamento dos dois MBSs aos dois QDs e que se considerou também amplitudes de superposição entre os férmions de Majorana, investigou-se a manifestação de estados moleculares mediados por tais férmions, pois o transporte eletrônico entre os QDs, no sistema proposto, se dá por meio do nanofio. Constatou-se padrões condizentes a níveis moleculares ligante e antiligante nas assinaturas dos estados ligados de Andreev (ABSs), originários da superposição dos MBSs, assim como nos níveis dos QDs que foram desdobrados após a formação molecular.
A model composed by a Kitaev wire within the topological phase with two quantum dots (QDs), one at each end of the nanowire, was theoretically studied. Two cases were analyzed: (i) Both the Majorana bound states (MBSs) at opposite ends of the nanowire are coupled to a single QD and (ii) both MBSs are coupled to the both QDs. For the first situation, three conditions were studied. In the first one, the profiles of nonlocal MBSs were verified, owing to the finite overlap between these states and the nearest QD; in the other two conditions, two profiles related to the couplings between the two MBSs and a QD, which also considered the overlap between the MBS. These profiles are known from previous experimental works as bowtie and diamond patterns. In the second case, in which both overlapped MBSs the manifestation of molecular states mediated by the MBSs was investigated, since electronic transport between the QDs , is mediated by nanowire. Patterns consistent with molecular levels of bonding and antibonding were found in the signatures of Andreev’s bound states (ABSs), originating from the overlapped MBSs, as well as in the split of the QDs levels due to the molecular formation via the transport through the nanowire.
A model composed by a Kitaev wire within the topological phase with two quantum dots (QDs), one at each end of the nanowire, was theoretically studied. Two cases were analyzed: (i) Both the Majorana bound states (MBSs) at opposite ends of the nanowire are coupled to a single QD and (ii) both MBSs are coupled to the both QDs. For the first situation, three conditions were studied. In the first one, the profiles of nonlocal MBSs were verified, owing to the finite overlap between these states and the nearest QD; in the other two conditions, two profiles related to the couplings between the two MBSs and a QD, which also considered the overlap between the MBS. These profiles are known from previous experimental works as bowtie and diamond patterns. In the second case, in which both overlapped MBSs the manifestation of molecular states mediated by the MBSs was investigated, since electronic transport between the QDs , is mediated by nanowire. Patterns consistent with molecular levels of bonding and antibonding were found in the signatures of Andreev’s bound states (ABSs), originating from the overlapped MBSs, as well as in the split of the QDs levels due to the molecular formation via the transport through the nanowire.
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Palavras-chave
Férmions de Majorana, Fio de Kitaev, Estados moleculares ligante e antiligante, Estados ligados de Andreev, Majorana fermions, Kitaev wire, Bonding and antibonding molecular states, Andreev bound states