ESPINTRÓNICA, ENERGÍA Y TOPOLOGÍA EN EL TRANSPORTE CUÁNTICO
Rosa López, David Sánchez
The emphasis of the proposed research is on novel concepts, prospects and fundamental breakthroughs in the field of quantum transport at the nanoscale. It is focused on three cutting-edge research sub-fields: Topology, Spintronics and Quantum Thermoelectricity. The advent of topological materials has caused a revolution in Condensed Matter Physics. These are rather peculiar systems that conduct at the edges (or surface) but are insulators in the bulk. This effect has its roots in the spin-orbit interaction, which twists the electronic states by closing the gap and induces a topological phase transition. Quite generally, topological materials are connected to spin-based electronics or Spintronics, where the spin degree of freedom yields new material functionalities. Topological superconductors exhibit even more exotic phenomena such as Majorana quasi-particles, which can be envisaged as a subtle combination of half electron and half hole and enable to perform quantum computation tasks by exchanging or braiding Majorana pairs. This proposal deals with probing Majorana physics in non-local transport and optical measurements and explores how Majorana pairs are altered when the system parameters acquire a time (for braiding) or spatial dependence (disorder) or even when a supercurrent is driven through them. Topological states may also manifest themselves in magnetic impurity systems in proximity with superconductivity and under the action of helical fields. We will
address the similarities among nearly zero energy Shiba states, their topological phases and those related to Majorana physics in nanowires. In addition to manipulating spin and charge degrees of freedom in nanoelectronic devices, our project considers Quantum Thermoelectricity to analyze the energy dynamics in systems coupled to both voltage and temperature biases. The practical goal is to convert waste heat into useful electricity using nanostructures that exhibit high conversion factors boosted by its quantum properties.
Equally exciting is the emerging idea that thermoelectrics provides a unifying concept across disciplines that help understand fundamental aspects of charge, spin and energy dynamics in nanostructures. Our research plan proposes to investigate efficiency of quantum thermoelectrical machines in the nonlinear transport regime and to assess the role of inelasticity and dephasing in nanoscale heat dissipation. We will formulate stationary and time dependent heat theoretical models valid for generic nanodevices (e.g., in non-adiabatic or thermoelectric RC quantum circuits), including topological systems. The role of the spin degree of freedom in thermoelectrical transport, or spin caloritronics will be discussed for hybrid impurity systems, a subject that helps reinforce the cohesion between the sub-fields of this project. Finally, we will address fundamental issues on quantum thermodynamics related to the entropy production or the amount of extracted information in topological systems, which will be of great important for our research roadmap.
Maria Isabel Alomar
Miguel A. Sierra