2010/01/05 by H. B. Rhee, S. Banerjee, E. R. Ylvisaker +2 · 22 citations
Materials Science · Physics and Astronomy · #Band gap #Condensed matter physics #Cuprate #Density of states #Doping #Electron #Fermi level #Fermi surface #Iron-based superconductors research #MXene and MAX Phase Materials #Materials science #Pairing #Physics #Pseudogap #Quantum mechanics #Quasi Fermi level #Semimetal #Superconductivity #Superconductivity in MgB2 and Alloys #Ternary operation #Valence (chemistry) #cond-mat.mtrl-sci #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.81.245114
published in Physical Review B 81(24) (American Physical Society) · 9 pages, 7 figures, 1 table
arxiv created 2010/01/05 · openalex publication_date 2010/06/15 · arxiv updated 2012/08/21 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The layered ternary sp conductor NaAlSi, possessing the iron-pnictide ``111'' crystal structure, superconducts at 7 K. Using density-functional methods, we show that this compound is an intrinsic (self-doped) low-carrier-density semimetal with a number of unusual features. Covalent Al-Si valence bands provide the holes, and free-electronlike Al 3s bands, which propagate in the channel between the neighboring Si layers, dip just below the Fermi level to create the electron carriers. The Fermi level (and therefore the superconducting carriers) lies in a narrow and sharp peak within a pseudogap in the density of states. The small peak arises from valence bands which are nearly of pure Si, quasi-two-dimensional, flat, and coupled to Al conduction bands. Isostructural NaAlGe, which is not superconducting above 1.6 K, has almost exactly the same band structure except for one missing piece of small Fermi surface. Certain deformation potentials induced by Si and Na displacements along the c axis are calculated and discussed. It seems likely that the mechanism of pairing is related to that of several other lightly doped two-dimensional nonmagnetic semiconductors (TiNCl, ZrNCl, HfNCl), which is not well understood but apparently not of phonon origin.