Abstract
Gaining a coherent picture and control of the transport properties at the nanoscale can lead to significant technological advancements. Important numerical, analytical and experimental works have demonstrated the possiblities of controlling the trans port properties of boundary driven quantum systems via the modulation of system parameters such as interactions, external fields, disorder and system-bath coupling. Different transport regimes can be achieved as a result. Emergent transport properties such as negative differential conductivity (NDC) and rectification can be exploited to engineer nonlinear devices such as diodes and transistors. The design of systems with such emergent transport properties is what this thesis has set out to explore. When a boundary driven quantum system is subjected to strong driving, the NDC phenomena occurs. We realize that a particular local magnetic field configuration andits mirror-symmetric can respectively suppress and reinforce the NDC phenomena to result in the largest and smallest spin current. This culminates in a giant rectification effect that persists in the thermodynamic limit. For the following, we characterize a boundary driven segmented XXZ spin chain with zero anisotropy on half the chain and non-zero anisotropy on the other half. This system becomes a perfect diode in the thermodynamic limit [1]. We first subject it to integrability-breaking terms and find that the type of transport i.e. ballistic or diffusive, in each half of the chain bears no relevance on the rectification effect. We explore non zero anisotropy on both halves of the chain, and find that the system has rectification only beyond an anisotropy value that increases with finite system sizes but it is no longer a perfect diode in the thermodynamic limit. We further investigate the phase transitions that occur in this model. We observe for finite-sized systems three transport regimes of ballistic, diffusive and insulating behaviour in the reverse bias, and two transport regimes of ballistic and diffusive transport for the forward bias. When subjected to dephasing, the rectification effect is strongly mitigated and we observe the emergence of a Quantum Zeno regime.