Variable-temperature lightwave-driven scanning tunneling microscope with a compact, turn-key terahertz source.

We report on a lightwave-driven scanning tunneling microscope based on a home-built microscope and a compact, commercial, and cost-effective terahertz-generation unit with a repetition rate of 100 MHz. The measurements are performed in an ultrahigh vacuum at temperatures between 8.5 and 300 K.

Strong transient magnetic fields induced by THz-driven plasmons in graphene disks.

Strong circularly polarized excitation opens up the possibility to generate and control effective magnetic fields in solid state systems, e.g., via the optical inverse Faraday effect or the phonon inverse Faraday effect.

Density-Dependence of Surface Transport in Tellurium-Enriched Nanograined Bulk Bi Te.

Three-dimensional topological insulators (3D TI) exhibit conventional parabolic bulk bands and protected Dirac surface states. A thorough investigation of the different transport channels provided by the bulk and surface carriers using macroscopic samples may provide a path toward accessing superior surface transport properties. Bi Te materials make promising 3D TI models; however, due to their complicated defect chemistry, these materials have a high number of charge carriers in the bulk that dominate the transport, even as nanograined structures.

Interface-Dominated Topological Transport in Nanograined Bulk Bi Te.

3D topological insulators (TI) host surface carriers with extremely high mobility. However, their transport properties are typically dominated by bulk carriers that outnumber the surface carriers by orders of magnitude. A strategy is herein presented to overcome the problem of bulk carrier domination by using 3D TI nanoparticles, which are compacted by hot pressing to macroscopic nanograined bulk samples.

Electrical tunability of terahertz nonlinearity in graphene.

Graphene is conceivably the most nonlinear optoelectronic material we know. Its nonlinear optical coefficients in the terahertz frequency range surpass those of other materials by many orders of magnitude. Here, we show that the terahertz nonlinearity of graphene, both for ultrashort single-cycle and quasi-monochromatic multicycle input terahertz signals, can be efficiently controlled using electrical gating, with gating voltages as low as a few volts.