Recent years the investigation of semiconductor/superconductor hybrid structures is intensively expanding, since these structures are promising platforms for novel qubits. The combination of low dimensionality, the presence of strong spin-orbit interaction in small band gap semiconductors and the macroscopic coherent state of superconductivity are expected to lead to novel topologically protected states, ideal for qubits. The control over electron density in semiconductor allows to form tuneable weak links between superconductors, even conductance channel with well-defined transmission. It allows to create new superconducting qubits, like Gatemons or Andreev-qubits.
So far most promising semiconductor/superconductor hybrids were developed based on semiconductor nanowires with epitaxially grown superconducting shell, thanks to the perfect superconductor-semiconductor interface. Recently novel shallow InAs and InSb two dimensional electron gas systems (2DEGS) were also developed, where the 2DEG is defined close enough to the surface of the semiconductor heterostructure to get superconducting proximity from the superconducting film on top, and far enough to keep high mobility. These heterostructures open exciting new alternatives, since the device geometry can be more advanced if it is engineered from 2DEG than from a 1D wire.
The goal of the PhD work is to develop quantum electronic devices from 2DEG/superconducting heterostructures. As a first step the fabrication technology of this new material platform has to be work out. The project will be carried out in close collaboration with leading grower groups, thus after understanding the properties of the 2DEG heterostructures, their structural improvement will be the next step. The final goal of the project is to engineer one almost perfectly transmitting conductance channel between superconducting leads to create Andreev qubit. So far Andreev qubits were studied in atomic junctions and semiconducting nanowires, however the control over the channel transmission is pure in these setups. Thanks to the well-developed techniques to form quantum point contacts in 2DEGs, better Andreev-qubits are expected to be realized.
During the phd work the applicant will be involved in the development of the 2DEG devices, their low temperature characterization with DC and also microwave techniques. The device fabrication will be carried out at MTA EK MFA cleanroom (supervised by Isvan Lukacs) while the characterization at BME Department of Physics (supervised by Szabolcs Csonka). The work is done in close collaboration with several European universities.
Knowledge of solid state physics, motivation for experimental work, experience in cleanroom work, English knowledge, basic programming and measurement automation experience.