This highlight focuses on the development of new thermometry required to study quantum materials and phenomena in high magnetic fields and at ultralow temperatures. The team has demonstrated that exceedingly small quartz tuning forks bathed in liquid 3He maintain a constant calibration that is magnetic field independent, thereby opening the use of these devices as new sensors of the response of quantum systems.
This highlight reports on the still poorly understood transition to an electron crystalline state (the Wigner crystal) in a two-dimensional system at extremely low densities, observable at low temperatures as a function of magnetic field. This experiment finds a surprising stabilization of the Wigner crystal arising from magnetic-field-induced spin alignment. Such electrically-delicate samples require the ultra-low-noise environment and experimental techniques available at the High B/T facility.
A material already known for its unique behavior is found to carry current in a way never before observed.
Decades ago a mechanism was proposed that described a quantum phase transition to an insulating ground state from a semi-metal (excitonic insulator, or EI) using very similar mechanics to those found in the BCS description of superconductivity. The discovery of this transition to an EI in InAs/GaSb quantum wells is striking not only for the long-sought experimental realization of important physics, but also the presence of recently proposed topological behavior.
Researchers discover that Sr1-yMn1-zSb2 (y,z < 0.1) is a so-called Weyl material that holds great promise for building devices that require far less power.
At the National MagLab, scientists have been experimenting for years on materials first dreamed up by the newest physics Nobel laureates decades ago.
The work by Chen et. al. explores the quantum hall effect (QHE) that develops in BiSbTeSe2 at low temperatures and high magnetic fields. BiSbTeSe2 is a topological insulator, meaning it is a bulk insulating material that at low temperatures develops a quantum mechanical state that allows conduction of electrons at the surface similar to a metal. The observation of the QHE in BiSbTeSe2 is further confirmation of the theory governing these unique materials.
SmB6 has been studied for a number of years and its observed behavior had presented investigators with a conflicting set of observations that resisted explanation until recently. The observation of quantum oscillations by Li et. al. in what is a bulk insulator confirm that SmB6 becomes a topological insulator at low temperatures. A topological insulator is a material that develops a unique quantum mechanical state on its surface, which allows electrons to flow in a fashion similar to a metal.
A superconducting ground state has been observed at T < 3.8 K in copper-doped Bi2Se3 single crystals. Topological superconductivity is predicted in this material, assuming the superconducting electrons follow the linear energy-momentum dispersion (Dirac-like) seen in graphene and other materials of current interest. However, this presumption had not yet been confirmed by quantum oscillation measurements.
Using one of the most powerful research magnets in the world, researchers have isolated signs of electrical current flowing along the surface of a topological insulator—an exotic material with promising electrical properties.