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Fragility of surface states in non-Wigner Dyson topological insulators
Alexander Altland, Piet W. Brouwer, Johannes Dieplinger +3
Topological insulators and superconductors support extended surface states protected against the otherwise localizing effects of static disorder. Specifically, in the Wigner-Dyson…
Homotopic classification of band structures: Stable, fragile, delicate, and stable representation-protected topology
Piet W. Brouwer, Vatsal Dwivedi
The topological classification of gapped band structures depends on the particular definition of topological equivalence. For translation-invariant systems, stable equivalence is d…
Non-Abelian holonomy of Majorana zero modes coupled to a chaotic quantum dot
Max Geier, Svend Krøjer, Felix von Oppen +3
If a quantum dot is coupled to a topological superconductor via tunneling contacts, each contact hosts a Majorana zero mode in the limit of zero transmission. Close to a resonance…
Fermi-arc metals
Maxim Breitkreiz, Piet W. Brouwer
We predict a novel metallic state of matter that emerges in a Weyl-semimetal superstructure with spatially varying Weyl-node positions. In the new state, the Weyl nodes are stretch…
Hinge States of Second-Order Topological Insulators as a Mach-Zehnder Interferometer
Adam Yanis Chaou, Piet W. Brouwer, Nicholas Sedlmayr
Three-dimensional higher-order topological insulators can have topologically protected chiral modes propagating on their hinges. Hinges with two co-propagating chiral modes can ser…
Finite-frequency spin conductance of a ferro-/ferrimagnetic-insulator|normal-metal interface
David A. Reiss, Piet W. Brouwer
The interface between a ferro-/ferrimagnetic insulator and a normal metal can support spin currents polarized collinear with and perpendicular to the magnetization direction. The f…
Phonon-limited Transport and Fermi Arc Lifetime in Weyl Semimetals
Francesco Buccheri, Alessandro De Martino, Rodrigo G. Pereira +2
Weyl semimetals harbor topological Fermi-arc surface states which determine the nontrivial charge current response to external fields. We here study the quasiparticle decay rate of…
Transition of laser-induced terahertz spin currents from torque- to conduction-electron-mediated transport
Pilar Jiménez-Cavero, Oliver Gueckstock, Lukáš Nádvorník +16
Spin transport is crucial for future spintronic devices operating at bandwidths up to the terahertz (THz) range. In F|N thin-film stacks made of a ferro/ferrimagnetic layer F and a…
Higher-order topological semimetals and nodal superconductors with an order-two crystalline symmetry
Sophia Simon, Max Geier, Piet W. Brouwer
Using a systematic relation between topological gapless phases in three dimensions and topological gapped phases in two dimensions, we identify four types of higher-order topologic…
Equilibrium current in a Weyl-semimetal - superconductor heterostructure
Kevin A. Madsen, Piet W. Brouwer, Maxim Breitkreiz
A heterostructure consisting of a magnetic Weyl semimetal and a conventional superconductor exhibits an equilibrium current parallel to the superconductor interface and perpendicul…
Theory of spin-Hall magnetoresistance in the AC (terahertz) regime
David A. Reiss, Tobias Kampfrath, Piet W. Brouwer
In bilayers consisting of a normal metal (N) with spin-orbit coupling and a ferromagnet (F), the combination of the spin-Hall effect, the spin-transfer torque, and the inverse spin…
Laser-induced terahertz spin transport in magnetic nanostructures arises from the same force as ultrafast demagnetization
R. Rouzegar, L. Brandt, L. Nadvornik +9
Laser-induced terahertz spin transport (TST) and ultrafast demagnetization (UDM) are central but so far disconnected phenomena in femtomagnetism and terahertz spintronics. Here, we…
Interference effects induced by a precessing easy-plane magnet coupled to a helical edge state
Kevin A. Madsen, Piet W. Brouwer, Patrik Recher +1
The interaction of a magnetic insulator with the helical electronic edge of a two-dimensional topological insulator has been shown to lead to many interesting phenomena. One of the…
Topological superconductivity in tripartite superconductor-ferromagnet-semiconductor nanowires
Josias Langbehn, Sergio Acero Gonzalez, Piet W. Brouwer +1
Motivated by recent experiments searching for Majorana zero modes in tripartite semiconductor nanowires with epitaxial superconductor and ferromagnetic-insulator layers, we explore…
Theory of the low-temperature longitudinal spin Seebeck effect
Rico Schmidt, Piet W. Brouwer
Using a simplified microscopic model of coupled spin and lattice excitations in a ferromagnetic insulator we evaluate the magnetic-field dependence of the spin Seebeck effect at lo…
Higher-order topological band structures
Luka Trifunovic, Piet W. Brouwer
The interplay of topology and symmetry in a material's band structure may result in various patterns of topological states of different dimensionality on the boundary of a crystal.…
Coherent Electron Optics with Ballistically Coupled Quantum Point Contacts
Jaan Freudenfeld, Max Geier, Vladimir Umansky +2
The realization of integrated quantum circuits requires precise on-chip control of charge carriers. Aiming at the coherent coupling of distant nanostructures at zero magnetic field…
Electrostatic potential shape of gate defined quantum point contacts
Max Geier, Jaan Freudenfeld, Jorge T. Silva +5
Quantum point contacts (QPC) are fundamental building blocks of nanoelectronic circuits. For their emission dynamics as well as for interaction effects such as the 0.7-anomaly the…
Disorder correction to the minimal conductance of a nodal-point semimetal
Zheng Shi, Björn Sbierski, Piet W. Brouwer
We consider the disorder-induced correction to the minimal conductance of an anisotropic two-dimensional Dirac node or a three-dimensional Weyl node. An analytical expression is de…
Long distance coherence of Majorana wires
Zheng Shi, Piet W. Brouwer, Karsten Flensberg +2
Theoretically, a pair of Majorana bound states in a topological superconductor forms a single fermionic level even at large separations, implying that the parity information is sto…
Symmetry-based indicators for topological Bogoliubov-de Gennes Hamiltonians
Max Geier, Piet W. Brouwer, Luka Trifunovic
We develop a systematic approach for constructing symmetry-based indicators of a topological classification for superconducting systems. The topological invariants constructed in t…
Large contribution of Fermi arcs to the conductivity of topological metals
Maxim Breitkreiz, Piet W. Brouwer
Surface-state contributions to the dc conductivity of most homogeneous metals exposed to uniform electric fields are usually as small as the system size is large compared to the la…
Proximity-induced gap in nanowires with a thin superconducting shell
Thomas Kiendl, Felix von Oppen, Piet W. Brouwer
Coupling a normal metal wire to a superconductor induces an excitation gap in the normal metal. In the absence of disorder, the induced excitation gap is strongly suppressed by fin…
Valley isospin of interface states in a graphene junction in the quantum Hall regime
Luka Trifunovic, Piet W. Brouwer
In the presence of crossed electric and magnetic fields, a graphene ribbon has chiral states running along sample edges and along boundaries between -doped and -doped regions…