In this talk I will present an overview of our work on gate induced superconductivity in transition metal dichalcogenides. After a short introduction about the technique of ionic liquid gating, I will discuss our observation of a gate-induced superconducting state in MoS2 that persists even when the thickness of the material is reduced to an individual monolayer. I will summarize the key...
We present a detailed scanning tunneling microscopy (STM) study of the thickness and temperature dependences of the CDW order parameter in 1T-VSe$_2$. We show that mapping the real-space charge order over a broad and well-characterized thickness range, unique to STM, provides essential insight. We introduce a robust derivation of the local order parameter and transition temperature based on...
We show that large spin-orbit interactions (SOI) in graphene can be achieved with TMD substrates. SOI is firstly revealed by weak anti-localization effect, and its analysis shows the spin relaxation time is ~0.2ps for all devices, thus strongly suggesting that the induced SOI originates from a modification of the graphene band structure. This is further confirmed by the observation of beating...
The intense research in layered materials showed the rich physics and promising prospective of 2D materials and monolayer.
Still one question remains open: what is the nature of the electronic motion between the layers of 2D materials? The reason for the limited number of investigations comes from an evident practical limit: high quality single crystals, have naturally a reduced thickness in...
The metastable 1T' polymorph of monolayer Mo and W dichalcogenides has recently been predicted to realize the quantum spin Hall insulator phase. Furthermore, the coexistence of this polymorph with the stable semiconducting 2H phase has been observed. In the 2H phase, point defects have widely been studied, while the effect of defects in the 1T' phase has not been investigated to date. Here, we...
Topological materials are a novel class of solids with outstanding properties protected by the interplay of topology and symmetry. Some of the phenomena that can be hosted in these materials, from dissipationless electron transport to spin filtering, could be very promising for many technological applications.
Nevertheless, the rarity of materials exhibiting a stable, topologically non-trivial...
With a few exceptions, all metallic Transition Metal Dichalcogenides (TMDs), whether in the 2h or 1t polytype, experience instabilities toward a distortion of the underlying lattice (often referred to as a charge density wave). With the advent of 2D materials, it has been shown that these instabilities persist down to the monolayer limit. The resulting effect on the electronic properties can...
Among graphene related materials, graphene nanoribbons (GNRs) – narrow stripes of graphene – have emerged as promising building blocks for nanoelectronic devices. The lateral confinement in GNRs opens a bandgap that sensitively depends on the ribbon width, allowing in principle for the design of GNR-based structures with tunable properties. However, structuring with atomic precision is...
Experimentalists at Empa recently succeeded in the on-surface synthesis of a variety of open-shell one-dimensional acenes. Their electronic spectra were obtained by means of scanning tunneling spectroscopy for molecules physisorbed on noble metal substrates. Comparison to theoretical predictions requires a proper treatment of the image charge effect in the renormalization of molecular energy...
Edge and π-electron topologies critically influence electronic properties of sp2 carbon frameworks. For example, presence of zigzag edge leads to emergence of localised non-bonding spin-polarised states, while armchair edge correspondingly supports a closed-shell electronic structure. Furthermore, special topologies of π-electron network leads to molecular systems with non-Kekulé structure...
Manganese self-assembles into atomic chains on the Si(001) reconstructed surface. Recently, our combined scanning tunneling microscopy, atomic force microscopy (AFM) and density functional theory (DFT) study revealed a simple necklace-like structure of the Mn chains. The DFT calculated adsorption energies support a single Mn atom adsorption H’ site, however no gain in energy promoting the...
Oxygen vacancies at the LAO/STO interface leave two vacant electrons, one of which stays localized at the Ti3+ ion and another joins the mobile 2DES. The localized electrons in double and higher-order configurations of the VOs may account for the interface ferromagnetism [1]. The mobile ones, coupled to phonon modes by strong e-ph interaction, form large multiphonon polarons fundamentally...
Two-dimensional electron gases (2DEGs) in SrTiO$_3$ arise in many configurations, of which the LaAlO$_3$/SrTiO$_3$ interface is a prominent example with remarkable properties such as gate-tunable superconductivity. I will present angle resolved photoemission spectroscopy measurements of the 2DEG induced at the (001) surface of SrTiO$_3$, providing insight into the subband structure that...
