27 research outputs found
Synthesis and characterisation of LK-99
Recently, two arXiv preprints (arXiv:2307.12008, arXiv:2307.12037) reported
signatures of superconductivity above room temperature and at ambient pressure,
striking worldwide experimental research efforts to replicate the results3-7,
as well as theoretical attempts to explain the purported superconductivity8-12.
The material of interest has chemical formula PbCu(PO)O,
where , and was named by the authors as LK-99. It belongs to lead
apatite family, and was synthesised from two precursors, lanarkite
(PbSOPbO) and copper phosphide (CuP). Here we performed a
systematic study on LK-99, starting from solid-state synthesis, followed by
characterisation and transport measurements. We did not observe any signatures
of superconductivity in our samples of LK-99
Machine learning approach to genome of two-dimensional materials with flat electronic bands
Many-body physics of electron-electron correlations plays a central role in
condensed mater physics, it governs a wide range of phenomena, stretching from
superconductivity to magnetism, and is behind numerous technological
applications. To explore this rich interaction-driven physics, two-dimensional
(2D) materials with flat electronic bands provide a natural playground thanks
to their highly localised electrons. Currently, thousands of 2D materials with
computed electronic bands are available in open science databases, awaiting
such exploration. Here we used a new machine learning algorithm combining both
supervised and unsupervised machine intelligence to automate the otherwise
daunting task of materials search and classification, to build a genome of 2D
materials hosting flat electronic bands. To this end, a feedforward artificial
neural network was employed to identify 2D flat band materials, which were then
classified by a bilayer unsupervised learning algorithm. Such a hybrid approach
of exploring materials databases allowed us to reveal completely new material
classes outside the known flat band paradigms, offering new systems for
in-depth study on their electronic interactions
Magnetization Signature of Topological Surface States in a Non-Symmorphic Superconductor
Superconductors with nontrivial band structure topology represent a class of materials with unconventional and potentially useful properties. Recent years have seen much success in creating artificial hybrid structures exhibiting the main characteristics of 2D topological superconductors. Yet, bulk materials known to combine inherent superconductivity with nontrivial topology remain scarce, largely because distinguishing their central characteristicāthe topological surface statesāhas proved challenging due to a dominant contribution from the superconducting bulk. In this work, a highly anomalous behavior of surface superconductivity in topologically nontrivial 3D superconductor In2Bi, where the surface states result from its nontrivial band structure, itself a consequence of the non-symmorphic crystal symmetry and strong spināorbit coupling, is reported. In contrast to smoothly decreasing diamagnetic susceptibility above the bulk critical field, Hc2, as seen in conventional superconductors, a near-perfect, Meissner-like screening of low-frequency magnetic fields well above Hc2 is observed. The enhanced diamagnetism disappears at a new phase transition close to the critical field of surface superconductivity, Hc3. Using theoretical modeling, the anomalous screening is shown to be consistent with modification of surface superconductivity by the topological surface states. The possibility of detecting signatures of the surface states using macroscopic magnetization provides a new tool for the discovery and identification of topological superconductor
Magnetization Signature of Topological Surface States in a Non-Symmorphic Superconductor
Superconductors with nontrivial band structure topology represent a class of materials with unconventional and potentially useful properties. Recent years have seen much success in creating artificial hybrid structures exhibiting the main characteristics of 2D topological superconductors. Yet, bulk materials known to combine inherent superconductivity with nontrivial topology remain scarce, largely because distinguishing their central characteristicāthe topological surface statesāhas proved challenging due to a dominant contribution from the superconducting bulk. In this work, a highly anomalous behavior of surface superconductivity in topologically nontrivial 3D superconductor In2Bi, where the surface states result from its nontrivial band structure, itself a consequence of the non-symmorphic crystal symmetry and strong spināorbit coupling, is reported. In contrast to smoothly decreasing diamagnetic susceptibility above the bulk critical field, Hc2, as seen in conventional superconductors, a near-perfect, Meissner-like screening of low-frequency magnetic fields well above Hc2 is observed. The enhanced diamagnetism disappears at a new phase transition close to the critical field of surface superconductivity, Hc3. Using theoretical modeling, the anomalous screening is shown to be consistent with modification of surface superconductivity by the topological surface states. The possibility of detecting signatures of the surface states using macroscopic magnetization provides a new tool for the discovery and identification of topological superconductor
Magnetization Signature of Topological Surface States in a NonāSymmorphic Superconductor
From Wiley via Jisc Publications RouterHistory: received 2021-04-28, rev-recd 2021-06-16, pub-electronic 2021-08-08Article version: VoRPublication status: PublishedFunder: European Union's Horizon 2020 research and innovation programme; Grant(s): 785219, 881603Funder: EPSRC; Id: http://dx.doi.org/10.13039/501100000266; Grant(s): EP/L01548XAbstract: Superconductors with nontrivial band structure topology represent a class of materials with unconventional and potentially useful properties. Recent years have seen much success in creating artificial hybrid structures exhibiting the main characteristics of 2D topological superconductors. Yet, bulk materials known to combine inherent superconductivity with nontrivial topology remain scarce, largely because distinguishing their central characteristicāthe topological surface statesāhas proved challenging due to a dominant contribution from the superconducting bulk. In this work, a highly anomalous behavior of surface superconductivity in topologically nontrivial 3D superconductor In2Bi, where the surface states result from its nontrivial band structure, itself a consequence of the nonāsymmorphic crystal symmetry and strong spināorbit coupling, is reported. In contrast to smoothly decreasing diamagnetic susceptibility above the bulk critical field, Hc2, as seen in conventional superconductors, a nearāperfect, Meissnerālike screening of lowāfrequency magnetic fields well above Hc2 is observed. The enhanced diamagnetism disappears at a new phase transition close to the critical field of surface superconductivity, Hc3. Using theoretical modeling, the anomalous screening is shown to be consistent with modification of surface superconductivity by the topological surface states. The possibility of detecting signatures of the surface states using macroscopic magnetization provides a new tool for the discovery and identification of topological superconductors
Novel approach to Room Temperature Superconductivity problem
A long-standing problem of observing Room Temperature Superconductivity is
finally solved by a novel approach. Instead of increasing the critical
temperature Tc of a superconductor, the temperature of the room was decreased
to an appropriate Tc value. We consider this approach more promising for
obtaining a large number of materials possessing Room Temperature
Superconductivity in the near future