Researchers Uncover Unique Properties of a Promising New Superconductor for Quantum Computing

 

A team of physicists led by the University of Minnesota has discovered that the unique superconducting metal Niobium diselenide (NbSe2) is more resilient when used as a very thin layer. The above diagram depicts the different s-, p-, and d-wave superconducting states in the metal. Credit: Alex Hamill and Brett Heischmidt, University of Minnesota

 

An international team of researchers led by the University of Minnesota has discovered that a rare superconducting metal is more resistant when used as a very thin layer. The study is the first step toward a bigger goal of understanding unconventional superconducting states in materials, which could probably be used in quantum computing in the coming times.

 

The teamwork includes four faculty members in the University of Minnesota’s School of Physics and Astronomy—Associate Professor Vlad Pribiag, Professor Rafael Fernandes, and Assistant Professors Fiona Burnell and Ke Wang—along with scientists at Cornell University and many other institutions. The research is published in Nature Physics, a regular, peer-reviewed scientific magazine published by Nature Research.

 

Niobium diselenide (NbSe2) is a superconducting metal, i.e. it can conduct electricity, or transfer electrons from one atom to another, with no resistance. It is not unusual for materials to act differently when they are at a very minor size, but NbSe2 has possibly beneficial properties. The scientists found that the material in 2D form (a very thin substrate only a few atomic layers thick) is a more resistant superconductor since it has a two-fold symmetry, which is very diverse from thicker samples of the same material.

 

Inspired by Fernandes and Burnell’s theoretical estimates of exotic superconductivity in this 2D material, Pribiag and Wang started to study atomically-thin 2D superconducting devices.

 

“We anticipated it to have a six-fold rotational pattern, like a snowflake,” Wang said. “Despite the six-fold structure, it only revealed two-fold behavior in the experiment.”

 

“This was one of the first times [this phenomenon] was detected in a real material,” Pribiag said.

 

The scientists recognized the newly-discovered two-fold rotational symmetry of the superconducting state in NbSe2 to the mixing between two closely opposing types of superconductivity, i.e. the conventional s-wave type—typical of bulk NbSe2—and an unconventional d- or p-type mechanism that appears in few-layer NbSe2. The two types of superconductivity have very parallel energies in this system. Because of this, they interrelate and compete with each other.

 

Pribiag and Wang told they later became aware that scientists at Cornell University were studying the same physics using a different experimental procedure, i.e. quantum tunneling measurements. They chose to combine their outcomes with the Cornell research and publish a more complete study.

 

Burnell, Pribiag, and Wang plan to form on these primary results to further study the properties of atomically thin NbSe2 in mixture with other exotic 2D materials, which could eventually lead to the use of unconventional superconducting states, such as topological superconductivity, to make quantum computers.

 

“What we want is a totally flat interface on the atomic scale,” Pribiag said. “We think this system will be able to give us an improved platform to examine materials to use them for quantum computing applications.”

References:

Heischmidt, Egon Sohn, Daniel Shaffer, Kan-Ting Tsai, Xi Zhang, Xiaoxiang Xi, Alexey Suslov, Helmuth Berger, László Forró, Fiona J. Burnell, Jie Shan, Kin Fai Mak, Rafael M. Fernandes, Ke Wang and Vlad S. Pribiag, 15 April 2021, Nature Physics.

https://doi.org/10.1038/s41567-021-01219-x