Dynamical Separation of Bulk and Edge Transport in HgTe-Based 2D Topological Insulators

Abstract

Topological effects in edge states are clearly visible on short lengths only, thus largely impeding their studies. On larger distances, one may be able to dynamically enhance topological signatures by exploiting the high mobility of edge states with respect to bulk carriers. Our work on microwave spectroscopy highlights the responses of the edges which host very mobile carriers, while bulk carriers are drastically slowed down in the gap. Though the edges are denser than expected, we establish that charge relaxation occurs on short timescales, and suggests that edge states can be addressed selectively on timescales over which bulk carriers are frozen. arXiv:1903.12391v3 [cond-mat.mes-hall]

Characterization of helical Luttinger liquids in microwave stepped-impedance edge resonators

“…The impedance mismatch generates reflection at each interface, in a geometry analogous to so-called steppedimpedance resonators, heavily used in acoustics or microwave design. This geometry is advantageous: i) the use of high frequencies (> 10 GHz) transport allows for using short devices (∼ 10 µm) in the ballistic limit ii) the capacitive coupling circumvents complications due to ohmic contacts: contact resistances which bring dissipation [36], as well as a complex behavior in the GHz range [37] iii) the geometry can be analyzed in terms of microwave networks [38], combining simple experimental setups [39][40][41], and straightforward interpretation.…”

Living on the edge: Topology, electrostatics, and disorder

“…Measuring quantum capacitance is therefore a common tool in studying electronic properties in the topological phase [68][69][70]. Experimental evidence of VP states in 3D TI where observed in quantum capacitance experiments [43], and recent experimental reports in 2D HgTe QWs show a values of the quantum capacitance exceeding the value due to the sole presence of topological edge states [71] (for a typical experimental setup see Fig. 8(a).…”

“…Here we are supposing the quantum contributions come only from (quasi) 1D edge states. In order to show this is indeed the case, one could measure the capacitance of systems of different length [43,71,74]. Doing this type of measurement, one can separate the geometric capacitance contribution from the quantum capacitance.…”

Majorana bound states in topological insulators with hidden Dirac points

“…A wider magnetic strip would suppress the superconductivity in the bulk, and the spectrum would become trivially gapless, excluding any possibility to generate bound states. The separate treatment of edge and bulk states is a desirable feature, which has been investigated in recent experiments [64,65].…”