Quantum transport in 2D topological materials

Topological protection results in coherent quantum states, which can be preserved even in the presence of lattice vibrations, often even at higher temperatures. If the dimension of the material is confined to 2D, such topologically protected states appear in the form of dissipationless edge channels. One example is the 2D topological insulator, namely the quantum spin Hall (QSH) states. If these dissipationless states can be stabilized at higher temperatures, this will open the door to a new era of low-energy consumption electronics. Realizing and detecting these states is one of the main focuses of the QuMat project.

Our approach to realizing the QSH states within QuMat is by MBE growth, a technique that can deposit the material layer by layer with atomic precision. Therefore, high-quality single crystalline thin films will be produced, which potentially should host the desired QSH states at their edges.

In Pillar 3.3, we will focus on the quantum transport measurement in such systems. First, we will characterize the thin films at low temperatures, and show the existence of the ballistic edge channels by measuring the quantized conductance. Then, we will induce superconductivity in the edge channels by means of the proximity effect. This allows us to explore the possibility of constructing the topological superconductivity.

We are looking for a motivated PhD candidate to experimentally study the Josephson effect in topological thin film-based devices. The candidate should have a background in condensed matter physics. While a background in mesoscopic physics or superconductivity would be preferable. In this PhD project, the candidate will learn how to fabricate the (superconducting) nanodevices using electron beam lithography and measure the electronic transport properties of the devices in ultra-low temperature (millikelvin) range in both low and high-frequency regimes.