Rearrangement of Energy Levels Between Energy Super-Bands Characterized by Second Chern Class

We generalize the dynamical analog of the Berry geometric phase setup to the quaternionic model of Avron et al. In our dynamical quaternionic system, the fast half-integer spin subsystem interacts with a slow two-degrees-of-freedom subsystem. The model is invariant under the 1:1:2 weighted SO(2) symmetry and spin inversion. There is one formal control parameter in addition to four dynamical variables of the slow subsystem. We demonstrate that the most elementary qualitative phenomenon associated with the rearrangement of the energy super-bands of our model consists of the rearrangement of one energy level between two energy superbands which takes place when the formal control parameter takes the special isolated value associated with the conical degeneracy of the semi-quantum eigenvalues. This qualitative phenomenon is of the topological origin, and is characterized by the second Chern class of the associated semi-quantum system. The correspondence between the number of redistributed energy levels and the second Chern number is confirmed through a series of examples.

Effect of the strain on spin-valley transport properties in MoS2 superlattice

The effect of the strain on the spin and valley dependent transport properties, including the conductance and polarization, through a monolayer MoS2 superlattice under Rashba spin–orbit coupling is theoretically investigated. It is found that the conductance strongly depends on the spin and valley degrees of freedom, and spin-inversion can be achieved by MoS2 superlattice. Also, the spin and valley dependent conductance in a monolayer MoS2 superlattice can be efficiently adjusted via strain and the number of the superlattice barriers. Moreover, it is demonstrated that both the magnitude and sign of the spin and valley polarization depend on the strain strength, the number of barriers, and electrostatic barrier height. Both full spin and valley polarized current (with 100% or − 100% efficiency) can be realized in a MoS2 superlattice under strain.

Efficient Solid-State Photon Upconversion Enabled by Spin Inversion at Organic Semiconductor Interface

We realized solid-state UC with 100 times higher efficiency than a conventional system by discovering a novel UC mechanism in bilayer organic semiconductor heterojunctions. The UC occurred through spin inversion during the charge separation and recombination at the interface. The key to the success was the triplet formation at the interface, as this could avoid the loss process during triplet diffusion, which is a problematic issue in conventional systems. As a result of this finding, efficient UC from near-infrared to visible light on flexible thin films under LED light excitation was made possible.

Efficient Solid-State Photon Upconversion Enabled by Spin Inversion at Organic Semiconductor Interface

We realized solid-state UC with 100 times higher efficiency than a conventional system by discovering a novel UC mechanism in bilayer organic semiconductor heterojunctions. The UC occurred through spin inversion during the charge separation and recombination at the interface. The key to the success was the triplet formation at the interface, as this could avoid the loss process during triplet diffusion, which is a problematic issue in conventional systems. As a result of this finding, efficient UC from near-infrared to visible light on flexible thin films under LED light excitation was made possible.

Kramers Degeneracy and Spin Inversion in a Lateral Quantum Dot

We show that the axial symmetry of the Bychkov–Rashba interaction can be exploited to produce electron spin-flip in a circular quantum dot, without lifting the time reversal symmetry. In order to elucidate this effect, we consider ballistic electron transmission through a two-dimensional circular billiard coupled to two one-dimensional electrodes. Using the tight-binding approximation, we derive the scattering matrix and the effective Hamiltonian for the considered system. Within this approach, we found the conditions for the optimal realization of this effect in the transport properties of the quantum dot. Numerical analysis of the system, extended to the case of two-dimensional electrodes, confirms our findings. The relatively strong quantization of the quantum dot can make this effect robust against the temperature effects.

Reduced-Dimensionality Quantum Dynamics Study of the 3Fe(CO)4 + H2 → 1FeH2(CO)4 Spin-inversion Reaction

Many chemical reactions of transition metal compounds involve a change in spin state via spin inversion, which is induced by relativistic spin-orbit coupling. In this work, we theoretically study the efficiency of a typical spin-inversion reaction, 3Fe(CO)4 + H2 → 1FeH2(CO)4. Structural and vibrational information on the spin-inversion point, obtained through the spin-coupled Hamiltonian approach, is used to construct three degree-of-freedom potential energy surfaces and to obtain singlet-triplet spin-orbit couplings. Using the developed spin-diabatic potential energy surfaces in reduced dimensions, we perform quantum nonadiabatic transition state wave packet calculations to obtain the cumulative reaction probability. The calculated cumulative reaction probability is found to be significantly larger than that estimated from the one-dimensional surface-hopping probability. This indicates the importance of both multidimensional and nuclear quantum effects in spin inversion for polyatomic chemical reaction systems.