Exploring the Possibility of Room Temperature Superconductivity in LK-99 Compounds

Sunday - September 17 2023, 05:39 UTC - 1 year ago

Researchers have used atom combinatorics and DFT+U calculations to uncover the most thermodynamically favorable structures of (1×1×2) Pb10−xCux(PO4)6O with x=1, where Cu atoms replace Pb(2a) and Pb(1b) sites, with a Cu-Cu distance of 3.692 A. This suggests the possibility of pressure-induced superconductivity, leading to a new avenue for the studies of high-temperature superconductivity in LK-99 compounds.

Computational theorists believe that the LK99 structure is promising and have discovered ways to improve LK99’s structure. The researchers think it is essential to gain a deeper understanding of the relationships between the LK-99 structure and properties, which could further open up new avenues for even high-temperature superconductivity (HTS). LK-99 was reported to have Tc as high as 400 K (127 ◦C) at ambient pressure. The replication of the LK99 experimental findings and the discovery of similar materials would revolutionize the field of superconductivity and open a wide range of next-generation technological applications, including but not limited to superconducting quantum interference devices (SQIDs), energy transmission systems, levitating trains, superconducting transistors, single-photon detection, quantum sensing, and quantum computing devices.

The s-wave pairing has been proposed for the possible HTS in LK-99. The specific arrangements of atoms with types of orbitals symmetry can, however, lead to either the s-wave or d-wave pairing mechanism. Further research is crucial to investigate and understand the complex structure property relationships in LK-99 compounds.

While the mechanism behind the potential room temperature superconductivity of LK-99 is unknown, it is argued that the long-range electron-phonon (e-ph) interactions cannot play an important role in inducing such phenomenon. Note, however, that there is no sufficient evidence yet for short-range e-ph interactions. Regardless of the range of e-ph interactions, the materials should possess the high electronic density of states (DOS) at the Fermi level in order to exhibit superconductivity. The flat band with a narrow bandwidth of 0.06 eV in the band structure of the lower-energy configuration of Pb9Cu(PO4)6O with one Cu substitution on a Pb(2a) site, indeed suggests that the LK-99 with such Cu arrangement might have higher DOS at the Fermi level. In the case of two Cu substitutions in the lower-energy configuration, the existence of a flat band around BZ center can lead to higher DOS than the other band which has a relatively larger bandwidth around the same region. Taking these electronic factors together with structural distortion into consideration, there might be a similar mechanism of phonon mediated long-range interactions as seen in other high-temperature superconductors, possibly with enhanced e-ph interactions in LK-99 compounds. Thus, it implies a need for a sophisticated quantum many-body theory to explain the potential quantum phases in LK-99. Due to the limitations of known physical models, the development of new techniques is critical.

Using the atom combinatorics-based approach within the supercell approximation and subsequently performing DFT+U optimization of 28 configurations (4 of (111) and 24 of (112) unit cells). Researchers found the most thermodynamically favorable structures of (1×1×2) Pb10−xCux(PO4)6O with x=1 where Cu atoms replace Pb(2a) and Pb(1b) sites, with Cu-Cu distance of 3.692 A. Moreover, the volume of Pb9Cu(PO4)6O is found to smaller than that of Pb10(PO4)6O, thus suggesting the possibility of pressure-induced superconductivity.

Conclusions .

Researchers have recently used atom combinatorics and DFT+U calculations to uncover the most thermodynamically favorable structures of (1×1×2) Pb10−xCux(PO4)6O. These results suggest the possibility of pressure-induced superconductivity, leading to a new avenue for the studies of high-temperature superconductivity. This study also highlighted the importance of quantum many-body techniques in understanding the potential mechanisms behind the room temperature superconductivity in LK-99 compounds.