Thermoelectric effects in quantum Hall systems beyond linear response

We consider a quantum Hall system with an antidot acting as an energy dependent scatterer. In the purely charge case, we find deviations from the Wiedemann-Franz law that take place in the nonlinear regime of transport. We also discuss Peltier effects beyond linear response and describe both effects using magnetic-field asymmetric transport coefficients. For the spin case such as that arising along the helical edge states of a two-dimensional topological insulator, we investigate the generation of spin currents as a result of applied voltage and temperature differences in samples attached to ferromagnetic leads. We find that in the parallel configuration the spin current can be tuned with the leads' polarization even in the linear regime of transport. In contrast, for antiparallel magnetizations the spin currents has a strict nonlinear dependence on the applied fields.Comment: 17 pages, 8 figure

Large thermoelectric power and figure of merit in a ferromagnetic-quantum dot-superconducting device

We investigate the thermoelectric properties of a quantum dot coupled to ferromagnetic and superconducting electrodes. The combination of spin polarized tunneling at the ferromagnetic-quantum dot interface and the application of an external magnetic field that Zeeman splits the dot energy level leads to large values of the thermopower (Seebeck coefficient). Importantly, the thermopower can be tuned with an external gate voltage connected to the dot. We compute the figure of merit that measures the efficiency of thermoelectric conversion and find that it attains high values. We discuss the different contributions from Andreev reflection processes and quasiparticle tunneling into and out of the superconducting contact. Furthermore, we obtain dramatic variations of both the magnetothermopower and the spin Seebeck effect, which suggest that in our device spin currents can be controlled with temperature gradients only.Comment: 9 pages, 6 figure

Cross thermoelectric coupling in normal-superconductor quantum dots

We discuss the nonlinear current of an interacting quantum dot coupled to normal and superconducting reservoirs with applied voltage and temperature differences. Due to the particle-hole symmetry introduced by the superconducting lead, the pure (subgap) thermoelectric response vanishes. However, we show that the Andreev bound states shift as the thermal gradient increases. As a consequence, the $I$--$V$ characteristic can be tuned with a temperature bias if the system is simultaneously voltage biased. This is a cross effect that occurs beyond linear response only. Furthermore, we emphasize the role of quasiparticle tunneling processes in the generation of high thermopower sensitivities.Comment: 6 pages, 5 figure

Transgenesis and Genome Editing in Poultry

The transgenic approach and precise editing of specific loci in the genome have diverse practical uses in animal biotechnology. Recent advances in genome-editing technology, including clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) have helped to generate highly valuable and quality-improved poultry. The production of transgenic and genome-edited birds mainly depends on primordial germ cells (PGCs), which are the progenitor cells of gametes, due to the unique system that is quite different from the mammalian system. This chapter introduces the basic physiology of avian PGCs and the latest PGC-mediated methodologies in transgenesis and genome editing of birds. Based on these techniques, future applications of precisely genome-modulated poultry are discussed to provide opportunities and benefits for humans

Nonlinear spin-thermoelectric transport in two-dimensional topological insulators

We consider spin-polarized transport in a quantum spin Hall antidot system coupled to normal leads. Due to the helical nature of the conducting edge states, the screening potential at the dot region becomes spin dependent without external magnetic fields nor ferromagnetic contacts. Therefore, the electric current due to voltage or temperature differences becomes spin polarized, its degree of polarization being tuned with the dot level position or the base temperature. This spin-filter effect arises in the nonlinear transport regime only and has a purely interaction origin. Likewise, we find a spin polarization of the heat current, which is asymmetric with respect to the bias direction. Interestingly, our results show that a pure spin current can be generated by thermoelectric means: when a temperature gradient is applied, the created thermovoltage (Seebeck effect) induces a spin-polarized current for vanishingly small charge current. An analogous effect can be observed for the heat transport: a pure spin heat flows in response to a voltage shift even if the thermal current is zero.This research was supported by MINECO under Grant No. FIS2011-23526, the Kavli Institute for Theoretical Physics through NSF Grant No. PHY11-25915 and the National Research Foundation of Korea (NRF) grants funded by the Korea government (MSIP) (Grant No. 2011-0030046).Peer Reviewe

Magnetic-field asymmetry of nonlinear thermoelectric and heat transport

Nonlinear transport coefficients do not obey, in general, reciprocity relations. We here discuss the magnetic-field asymmetries that arise in thermoelectric and heat transport of mesoscopic systems. Based on a scattering theory of weakly nonlinear transport, we analyze the leading-order symmetry parameters in terms of the screening potential response to either voltage or temperature shifts. We apply our general results to a quantum Hall antidot system. Interestingly, we find that certain symmetry parameters show a dependence on the measurement configuration. © IOP Publishing and Deutsche Physikalische Gesellschaft.SYH and ML were supported by the National Research Foundation (NRF) grant funded by the Korea government (MSIP) (no. 2011-0030046). DS and RL were supported by MINECO grant no. FIS2011-2352.Peer Reviewe

Proposal for a local heating driven spin current generator

We propose a two-terminal spin-orbit interferometer with a hot molecule inserted in one of its arms to generate pure spin currents. Local heating is achieved by coupling the vibrational modes of the molecule to a third (phononic) reservoir. We show that this spin caloritronic effect is due to the combined influence of spin-dependent wave interference and inelastic scattering. Remarkably, the device converts heat flow into spin-polarized current even without applying any voltage or temperature difference to the electronic terminals. © 2013 AIP Publishing LLC.The authors acknowledge the support from MECD under Grant Nos. FIS2011-23526 and CSD2007-00042 (CPAN), and the National Research Foundation (NRF) grant funded by the Korea government (MSIP) (No. 2011-0030046).Peer Reviewe