Cholesky Decomposition in Spin-Free Dirac-Coulomb Coupled-Cluster Calculations.

We present an implementation for the use of Cholesky decomposition (CD) of two-electron integrals within the spin-free Dirac-Coulomb (SFDC) scheme that enables to perform high-accuracy coupled-cluster (CC) calculations at costs almost comparable to those of their nonrelativistic counterparts. While for nonrelativistic CC calculations, atomic-orbital (AO)-based algorithms, due to their significantly reduced disk-space requirements, are the key to efficient large-scale computations, such algorithms are less advantageous in the SFDC case due to their increased computational cost in that case. Here, molecular-orbital (MO)-based algorithms exploiting the CD of the two-electron integrals allow us to reduce disk-space requirements and lead to computational cost in the CC step that is more or less the same as in the nonrelativistic case.

Laser Control of Resonance Tunneling via an Exceptional Point.

According to the familiar Breit-Wigner formula, tunneling through a potential barrier is strongly enhanced when the energy of the projectile is equal to the resonance energy. Here we show how a weak continuous wave laser can qualitatively change the character of resonance tunneling, and enforce a sudden and total suppression of the transmission by inducing an exceptional point (EP, special non-Hermitian degeneracy). Our findings are relevant not only for laser control of transmission in the resonance tunneling diodes, but also in the context of electron scattering through any type of metastable (e.