Many-body interactions in quantum wires

• Main Author: Graham, Abi Claire
• Published: University of Cambridge 2004
• Subjects: 537.622
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599591

The first part of this thesis describes transport measurements of long quantum wires, which are affected by disorder. The resulting additional features in the conductance are characterised, and the results are discussed in the context of the Luttinger liquid model. Realistic strategies for controlling disorder in long wires are suggested, which should eliminate many of the problems associated with experimental studies of Luttinger liquids. Disorder effects are further investigated using a new lithography technique called Erasable Electrostatic Lithography (EEL). A scanning probe tip at a fixed voltage is used to locally charge surface states above a long disordered quantum wire. This allows the potential of the disordered wire to be manipulated, with the creation of microconstrictions and quasi-bound states inside the wire. The importance of electron-electron interactions in short 1D systems was demonstrated in 1996 by the discovery of the 0.7 structure. This is an additional quasi-plateau in the conductance at a value of around 0.7(2<i>e</i>²/<i>h</i>) and is a universal phenomenon in quantum wires. The main result of this thesis is the discovery of non-quantised conductance structures at the crossings of spin-split 1D subbands which have similar characteristics to the 0.7 structure. We call these new structures 0.7 analogues. It is shown that the 0.7 analogue is accompanied by a spontaneous splitting and abrupt restructuring of energy levels in the region of the crossing, which is thought to be an exchange effect. We believe that this gives valuable new insight into the origin of the 0.7 structure.