Thermospin Effects Research Articles

Optically Assisted Thermoelectric and Thermospin Effect in a Quantum Dot Structure

The thermoelectric effect in a quantum dot structure is theoretically studied with the application of circularly polarized light. We find that at low temperature, the polarized light induces the antiresonant transport of spin-up electron through this structure, leading to the significant contribution of the spin-up electron to the thermoelectric effect. Alternatively, at high temperature, the opposite results come into being, i.e., the transport of the spin-down electron plays a dominant role in driving the thermoelectric effect. Thus, apparent thermospin effect occurs in this structure, which is strongly dependent on temperature. In addition, it shows that the thermoelectric effect is efficiently enhanced and the thermospin effect is further manipulated by the presence of electron interaction.

A proposal for time-dependent pure-spin-current generators

We propose a pure-spin-current generator based on a single level quantum dot (QD) device subjected to time-dependent magnetic fields. Under low temperature and high magnetic fields, the spin-dependent Seebeck coefficient in the transition regime is rapidly enhanced by several orders of magnitude larger than that in the steady regime. This fact is attributed to a delay effect of the electron transmission probability with respect to the split of the QD energy level. When a temperature gradient is applied across the device, the pure spin current emerges. The findings here suggest a feasible way of enhancing thermospin effects and generating the pure spin current by time-dependent external fields.

Thermospin effects in parallel coupled double quantum dots in the presence of the Rashba spin-orbit interaction and Zeeman splitting

The thermoelectric and the thermospin transport properties, including electrical conductivity, Seebeck coefficient, thermal conductivity, and thermoelectric figure of merit, of a parallel coupled double-quantum-dot Aharonov—Bohm interferometer are investigated by means of the Green function technique. The periodic Anderson model is used to describe the quantum dot system, the Rashba spin—orbit interaction and the Zeeman splitting under a magnetic field are considered. The theoretical results show the constructive contribution of the Rashba effect and the influence of the magnetic field on the thermospin effects. We also show theoretically that material with a high figure of merit can be obtained by tuning the Zeeman splitting energy only.

Thermospin phenomena in a quantum dot attached to ferromagnetic leads: Role of asymmetry and alignment

We study the thermospin effects in a system consisting of a quantum dot coupled to ferromagnetic leads. It is shown that sign reversal and oscillation of spin Seebeck coefficient are indicated as a function of device parameters. When the magnetizations of the leads are formed in parallel alignment, the spin Seebeck coefficient and the spin-FOM have their maximum values for the symmetric dot-lead coupling case. However, in the antiparallel case, the optimal device parameters depend mainly on the strength of the magnetic field.

Thermospin effects of a quasi-one-dimensional system in the presence of spin-orbit interaction

The authors investigate the effect of Rashba spin-orbit interaction (SOI) and external magnetic field on the thermospin properties of a quasi-one-dimensional ballistic electron system. Spin analogs to the thermoelectric Seebeck coefficient and figure of merit (FOM) are defined and studied. Sign reversal and oscillation of spin Seebeck coefficient are indicated as a function of junction parameters. With the increase of SOI strength, the spin Seebeck coefficient oscillates more rapidly and the intervals between adjacent peaks are narrowed. Because large thermal conductance is induced by the more conducting paths, spin-FOM in the presence system is smaller than that of a quantum dot device.

Erratum: Thermospin effects in a quantum dot connected to ferromagnetic leads [Phys. Rev. B.79, 081302 (2009)

Erratum: Thermospin effects in a quantum dot connected to ferromagnetic leads [Phys. Rev. B.<b>79</b>, 081302 (2009)

Coupled waves of linear velocity, angular velocity, and temperature in a liquid with internal rotation

Equations of motion for a locally nonequilibrium liquid with internal rotation are derived, and the thermospin effect is considered. It is demonstrated that high-frequency transverse coupled waves of linear velocity, angular velocity of internal rotation, and temperature may propagate a liquid with internal rotation. A dispersion relation and a frequency dependence of the damping ratio are deduced. Comparison between theoretical and experimental values of the transverse sound velocity dispersion shows their satisfactory agreement. Low-frequency transverse waves do not penetrate into the liquid: they decay over a distance on the order of the wavelength. It is shown that frequencies and their corresponding wavenumbers exist in a liquid with internal rotation at which either waves do not decay or a phase shift in the skin layer is absent. It is found that the excitation spectrum may contain a cutoff frequency or an energy gap due to interaction between the linear and angular velocity fields. The dispersion and damping ratio for the coupled waves near synchronism points, where uncoupled waves resonantly interact with each other, are determined.

Thermospin effects in a quantum dot connected to ferromagnetic leads

We study a system composed of a quantum dot in contact with ferromagnetic leads held at different temperatures. Spin analogs to the thermopower and thermoelectric figure of merit are defined and studied as a function of junction parameters. It is shown that in contrast to bulk ferromagnets, the spin-thermopower coefficient in a junction can be as large as the Seebeck coefficient, resulting in a large spin figure of merit. In addition, it is demonstrated that the junction can be tuned to supply only spin current but no charge current. We also discuss experimental systems where our predictions can be verified.