Physicists Explain Transition Between Different Types of Superconductivity

Physicists from HSE MIEM in collaboration with colleagues from MIPT and other universities have formulated a theory capable of explaining the transition between different superconductivity types, revealing an intertype regime characterised by exotic magnetic properties. This discovery can serve as the foundation for the development of sensors with enhanced sensitivity and accuracy, capable of functioning in conditions where traditional sensors are less effective. The study has been published in Communications Physics.

Every conductor possesses resistance, causing a portion of the current’s energy to dissipate as heat within the wire. In the early twentieth century, the phenomenon of superconductivity was discovered—the capacity of a material to conduct electric current without any loss of energy. But as of now, superconductivity can only be achieved at low temperatures. Once technological advancements make superconductivity possible at room temperature, humanity will achieve a revolution in electronics. 

There are two main types of superconductors; the first type, which comprises mercury and aluminium, precludes the existence of a magnetic field within the superconductor. The second type, which includes niobium and vanadium, permits the presence of a magnetic field. These two types of superconductors are typically represented by different materials. However, there is also a unique class of materials known as ferromagnetic superconductors, where a transition between different types of superconductivity is possible.

Scientists from HSE University, MIPT, and several other Russian and international institutions have investigated the transition between different types of superconductivity in ferromagnetic superconductors. The team has discovered that such intertype transition occurs within a specific temperature range, lying between the temperature of magnetic ordering and the superconducting transition temperature. 

In the intertype transition state, intricate spatial configurations emerge within the material, encompassing patterns of magnetisation and superconducting condensate. These patterns are sensitive to changes in external conditions, such as temperature, magnetic field, or electric current. 

Metals or semiconductors, whose resistance changes with temperature, are used to produce thermometers—temperature sensors. Semiconductors, whose resistance varies with changes in illumination, are used in the production of sensors that activate lighting in low-light conditions or when someone passes by. The sensitivity of patterns in a magnetic superconductor could serve as the foundation for a new type of sensor.

Alexei Vagov
Co-author of the paper, Director of the Centre for Quantum Metamaterials, MIEM HSE

Highly sensitive sensors for temperature, magnetic fields, or electric fields are essential for monitoring minute changes in these parameters. This can be critical for tasks such as creating precise images in MRI (using magnetic field sensors), conducting electrocardiography and electroencephalography (electric field sensors), and monitoring high-precision measuring equipment where its component properties are temperature-dependent.

The appearance of patterns in magnetic superconductors cannot be explained within the framework of the standard Ginzburg–Landau approach, which is commonly used to describe the properties of superconductors at superconducting transition temperatures. We were able to capture the required effect through an expanded Ginzburg–Landau theory, an approach we had been developing over the past decade. This approach makes it possible to accurately describe the transition between different types of superconductivity and to observe the emergence of exotic magnetic properties in the intertype regime.

Arkady Shanenko
Co-author of the paper, Chief Research Fellow at the Centre for Quantum Metamaterials, MIEM HSE

The scientists emphasise that the findings from their study are universally applicable: intertype superconductivity and patterns must manifest in any material where superconductivity is compatible with magnetic properties.

Back in 2018, we published a paper about our discovery in Science Advances. Then, for the first time globally, we experimentally demonstrated the formation of Meissner and vortex domains in magnetic superconductors. These findings sparked a lively discussion in the scientific community and necessitated the development of a microscopic theory that precisely describes the processes occurring when combining the two phases (magnetic and superconducting) within the same material. This present work has been the result of these efforts.

Vasily Stolyarov
Co-author of the paper, Director of the Centre for Advanced Mesoscience and Nanotechnology, MIPT

IQ

February 27