Predoctoral topological superconductivity

 

PhD position in the field of Topological superconductivity

We are seeking a highly motivated candidate with a strong interest in experimental Solid-State Physics, Surface Science, or Quantum Nanoscience to pursue PhD research at the Materials Physics Center in collaboration with the Donostia International Physics Center in San Sebastián, Spain.

Project Overview:

Condensed matter can be classified with respect to the topology of its electronic band structure. When two phases of different topology meet, their gap must close to enable the transition. As a result, edge states appear. When this happens between superconductors of different topology, the edge states are Majorana states with extraordinary properties. Majoranas self-annihilate and they obey non-Abelian statistic, leading to complex unitary transformations of the Majoranas as they exchange among them. These extraordinary states can be made using magnetic atoms or molecules with the scanning tunneling microscope (STM) on superconducting substrates. This is because magnetic atoms or molecules on a superconductor locally destroy the superconducting state, giving rise to states inside the superconductor's gap.

Research Goals:

The project is to perform topological quantum computing using magnetic atomic nanostructures on superconducting surfaces [1]. When you put a chain of atoms with interatomic distances on the order of the superconductor lattice parameter, you can create bands of single-particle states that pair, leading to the creation of a new superconductor inside the initial superconductor. The new superconductor can show different topological properties. In this way, Majorana states can be created and possibly manipulated with the STM.

Candidate Expectations:

The ideal canditate will study superconducting surfaces with the STM, modify them on the atomic scale, and create new magnetic structures that will lead to exotic topological phases. The appearing Majoranas will be manipulated altering the conditions of the STM junction with the aim of exchanging Majoranas.

Position Details:

The position is available upon agreement, with a planned duration of three to four years. For more information, please contact Prof. Dr. Nicolas Lorente, Nicolas.lorente at ehu.eus or Dr. Deung-Jang Choi, djchoi at dipc.org. Applications must include a brief statement of interest, CV including an academic transcript with the obtained marks, and at least one reference with contact details to be sent: djchoi at dipc.org .

Reference:

[1] Atomic manipulation of in-gap states in the β−Bi2Pd superconductor, Phys. Rev. B 104, 045406 (2021)

Figure a is the experimental differential conductance (colormap) of an STM junction when the tip is moving above the four Cr atoms of a Cr4 spin chain (Y-axis), as a function of the applied bias (X-axis). Figure b is the corresponding calculation, showing the same features as in the epxeriment (at positive bias, two clear peaks at the edges of the chain for larger bias, and a central peak for the lower bias, and at negative bias dimmer peaks). Figure b is the prediction for a Cr8 chain and d is the prediction for Cr20 showing two clear Majorana states at the edges of the chain. For more information check out Ref. [1].