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Femtosecond concerted rotation of molecules on a 2D material interface
Kiana Baumgärtner, Misa Nozaki, Marvin Reuner +20
Interfaces between molecules and 2D materials exhibit energy-driven functionalities, wherein charge transfer directs molecular motion. Unlike equilibrium systems, where molecular a…
Phonon Self-Energy Corrections: To Screen, or Not to Screen
Jan Berges, Nina Girotto, Tim Wehling +2
First-principles calculations of phonons are often based on the adiabatic approximation and on Brillouin-zone samplings that might not always be sufficient to capture the subtletie…
A full gap above the Fermi level: the charge density wave of monolayer VS2
Camiel van Efferen, Jan Berges, Joshua Hall +15
In the standard model of charge density wave (CDW) transitions, the displacement along a single phonon mode lowers the total electronic energy by creating a gap at the Fermi level,…
Frequency-dependent substrate screening of excitons in atomically thin transition metal dichalcogenide semiconductors
A. Steinhoff, T. O. Wehling, M. Rösner
Atomically thin layers of transition metal dichalcogenides (TMDCs) exhibit exceptionally strong Coulomb interaction between charge carriers due to the two-dimensional carrier confi…
The dielectric impact of layer distances on exciton and trion binding energies in van der Waals heterostructures
M. Florian, M. Hartmann, A. Steinhoff +6
The electronic and optical properties of monolayer transition-metal dichalcogenides (TMDs) and van der Waals heterostructures are strongly subject to their dielectric environment.…
Excitons versus electron-hole plasma in monolayer transition metal dichalcogenide semiconductors
Alexander Steinhoff, Matthias Florian, Malte Rösner +3
When electron-hole pairs are excited in a semiconductor, it is a priori not clear if they form a fermionic plasma of unbound particles or a bosonic exciton gas. Usually, the excito…
Non-invasive control of excitons in two-dimensional materials
Christina Steinke, Daniel Mourad, Malte Rösner +5
We investigate how external screening shapes excitons in two-dimensional (2d) semiconductors embedded in laterally structured dielectric environments. An atomic scale view of these…
Midgap states and band gap modification in defective graphene/h-BN heterostructures
B. Sachs, T. O. Wehling, M. I. Katsnelson +1
The role of defects in van der Waals heterostructures made of graphene and hexagonal boron nitride (h-BN) is studied by a combination of ab initio and model calculations. Despite t…
Non-magnetic ground state of Ni adatoms on Te-terminated bismuth chalcogenide topological insulators
M. Vondracek, J. Honolka, L. Cornils +20
We report on the quenching of single Ni adatom moments on Te-terminated Bi2Te2Se and Bi2Te3 topological insulator surfaces. The effect becomes manifested as a missing X-ray magneti…
Nonequilibrium Carrier Dynamics in Transition Metal Dichalcogenide Semiconductors
Alexander Steinhoff, Matthias Florian, Malte Rösner +4
When exploring new materials for their potential in (opto)electronic device applications, it is important to understand the role of various carrier interaction and scattering proce…
Correlated electron behavior of metalorganic molecules: insights from density functional theory combined with many-body effects using exact diagonalization
Sumanta Bhandary, Malte Schüler, Patrik Thunström +5
A proper theoretical description of electronic structure of the 3d orbitals in the metal centers of functional metalorganics is a challenging problem. In this letter, we apply dens…
Wannier Function Approach to Realistic Coulomb Interactions in Layered Materials and Heterostructures
M. Rösner, E. Şaşıoğlu, C. Friedrich +2
We introduce an approach to derive realistic Coulomb interaction terms in free standing layered materials and vertical heterostructures from ab-initio modelling of the correspondin…
Separation of ultrafast spin currents and spin-flip scattering in Co/Cu(001) driven by femtosecond laser excitation via the complex MOKE
J. Wieczorek, A. Eschenlohr, B. Weidtmann +5
Ultrafast magnetization dynamics in metallic heterostructures consists of a combination of local demagnetization in the ferromagnetic constituent and spin-dependent transport contr…
Dirac materials
T. O. Wehling, A. M. Black-Schaffer, A. V. Balatsky
A wide range of materials, like d-wave superconductors, graphene, and topological insulators, share a fundamental similarity: their low-energy fermionic excitations behave as massl…
Phase Diagram of Electron Doped Dichalcogenides
M. Rösner, S. Haas, T. O. Wehling
Using first principle calculations, we examine the sequence of phases in electron doped dichalcogenides, such as recently realized in field-gated MoS. Upon increasing the elect…
Controllable magnetic doping of the surface state of a topological insulator
T. Schlenk, M. Bianchi, M. Koleini +11
A combined experimental and theoretical study of doping individual Fe atoms into Bi2Se3 is presented. It is shown through a scanning tunneling microscopy study that single Fe atoms…
Two-Site Kondo Effect in Atomic Chains
N. Néel, R. Berndt, J. Kröger +3
Linear CoCu_nCo clusters on Cu(111) are fabricated by means of atomic manipulation. They represent a two-site Kondo system with tunable interaction. Scanning tunneling spectroscopy…
Ultrafast transport of laser-excited spin polarized carriers in Au/Fe/MgO(001)
Alexey Melnikov, Ilya Razdolski, Tim O. Wehling +6
A time domain approach to probe hot carrier-induced spin dynamics is demonstrated. The experiments are performed in epitaxial Au/Fe/MgO(001), where spin-polarized hot carriers are…
Controlling the Kondo Effect in CoCu_n Clusters Atom by Atom
N. Neel, J. Kroeger, R. Berndt +3
Clusters containing a single magnetic impurity were investigated by scanning tunneling microscopy, spectroscopy, and ab initio electronic structure calculations. The Kondo temperat…