Model Prediction of Self-Rotating Excitons in Two-Dimensional Transition-Metal Dichalcogenides

Using the quasiclassical concept of Berry curvature we demonstrate that a Dirac exciton—a pair of Dirac quasiparticles bound by Coulomb interactions—inevitably possesses an intrinsic angular momentum making the exciton effectively self-rotating. The model is applied to excitons in two-dimensional transition metal dichalcogenides, in which the charge carriers are known to be described by a Dirac-like Hamiltonian. We show that the topological self-rotation strongly modifies the exciton...

Read more

Spin pumping and shot noise in ferrimagnets: bridging ferro- and antiferromagnets

A combination of novel technological and fundamental physics prospects has sparked a huge interest in pure spin transport in magnets, starting with ferromagnets and spreading to antiferro- and ferrimagnets. We present a theoretical study of spin transport across a ferrimagnet–nonmagnetic conductor interface, when a magnetic eigenmode is driven into a coherent state. The obtained spin current expression includes intra- as well as cross-sublattice terms, both of which are essential for a...

Read more

Ground-State Cooling of a Mechanical Oscillator by Interference in Andreev Reflection

Reaching the quantum ground state of a nanomechanical oscillator consisting of millions of atoms would allow to study the weirdness of quantum mechanics in a new regime. Suspended carbon nanotubes can oscillate at different frequencies similar to a guitar string. In this paper, we propose a novel way to cool such a system towards the absolute zero of temperature, when these modes are in their quantum ground state with the minimal possible energy. Just like in an ordinary refrigerator electric...

Read more

Super-Poissonian Shot Noise of Squeezed-Magnon Mediated Spin Transport

Microscopic particles called electrons carry the charge currents which underlie the modern electronic devices. A novel technological paradigm based on magnets relies upon spin currents carried by fundamentally different particles - magnons, carrying a quantum of spin. In this paper, we show that interactions lead to a new exotic particle called squeezed-magnon, consisting of a quantum conglomerate of several magnons and, thus, carrying an angular momentum different from the fundamental quantum....

Read more

Electron and electron-hole quasiparticle states in a driven quantum contact

We study the many-body electronic state created by a time-dependent drive of a mesoscopic contact. The many-body state is expressed manifestly in terms of single-electron and electron-hole quasiparticle excitations with the amplitudes and probabilities of creation which depend on the details of the applied voltage. We experimentally probe the time dependence of the constituent electronic states by using an analog of the optical Hong-Ou-Mandel correlation experiment where electrons emitted from...

Read more

Ultrafast pseudospin dynamics in graphene

We address a long standing problem of pseudospin control in graphene from both experimental and theoretical point of view. The outcome of this work is twofold.
First, we provide a conclusive evidence of the anisotropic photocarrier occupation (i. e. pseudospin polarization) in graphene caused by interaction between pseudospin and linearly polarized light, see left figure. This peculiar phenomenon has long been discussed in numerous theoretical papers but its direct observation in a truly single...

Read more

Ground state cooling of a carbon nano-mechanical resonator by spin-polarized current

We study the non-equilibrium regime of a mechanical resonator at low temperature realized with a suspended carbon nanotube quantum dot contacted to two ferromagnets. Due to spin- orbit interaction and/or an external magnetic gradient, the spin on the dot couples directly to the flexural eigenmodes. Owing to this interaction, the nanomechanical motion induces spin-flips of the electrons passing through the nanotube. When a finite voltage is applied, a spin-polarized current causes either heating...

Read more

"Smile"-gap in the density of states of a cavity between superconductors

The density of Andreev levels in a normal metal (N) in contact with two superconductors (S) is known to exhibit an induced minigap related to the inverse dwell time. We predict a small secondary gap just below the superconducting gap edge - a feature that has been overlooked so far in numerous microscopic studies of the density of states in SNS structures. In a generic structure with N being a chaotic cavity, the secondary gap is the widest at zero phase bias. It closes at some finite phase...

Read more