Topological Semimetal KAlGe with Novel Electronic Instability

Abstract

Compounds with the anti-PbFCl structure exhibit a variety of electronic instabilities and intriguing physical properties. NaAlSi and NaAlGe are similar topological nodal-line semimetals, but they have distinct properties. NaAlSi is a superconductor at 6.8 K, whereas NaAlGe is an insulator with a pseudogap of approximately 100 K. Using the potassium-indium flux method, we succeeded in synthesizing a single crystal of KAlGe, a new anti-PbFCl compound. First principles electronic structure calculations reveal that KAlGe is isoelectronic with NaAlSi and NaAlGe. KAlGe undergoes a metal-to-metal transition at 89 K and exhibits no superconductivity above 1.8 K. The low temperature phase has significantly lower carrier density and extremely high mobility, similar to Dirac electron systems. Furthermore, X-ray diffraction experiments show a structural change that breaks the fourfold symmetry during the phase transition. Electron-phonon interactions may be responsible for superconductivity in NaAlSi, whereas excitonic electron-hole interactions are thought to play an important role in KAlGe and possibly NaAlGe. Our findings demonstrate that fascinating physics lies within the compound family.

12 pages, 12 figures, accepted by Chemistry of Materials

References in corpus (28)

• Titanic Magnetoresistance in WTe2
• Nematic order in iron superconductors - who is in the driver's seat?
• Dirac Cone Protected by Non-Symmorphic Symmetry and 3D Dirac Line Node in ZrSiS
• LiFeAs: An Intrinsic FeAs-based Superconductor with Tc = 18K
• Nematic and meta-nematic transitions in the iron pnictides
• Orbital-driven nematicity in FeSe
• Large nonsaturating magnetoresistance and signature of non-degenerate Dirac nodes in ZrSiS
• Structure and superconductivity of LiFeAs
• Nematic quantum critical point without magnetism in FeSe1-xSx superconductors
• Quantum Hall effect in a bulk antiferromagnet EuMnBi${}_2$ with magnetically confined two-dimensional Dirac fermions
• Topological quantum materials from the viewpoint of chemistry
• Unconventional mass enhancement around the Dirac nodal loop in ZrSiS
• Symmetry breaking via orbital-dependent reconstruction of electronic structure in uniaxially strained NaFeAs
• A new 111 type iron pnictide superconductor LiFeP
• Detection of multipolar orders in the spin-orbit-entangled 5d Mott insulator Ba2MgReO6
• Multi-step topological transitions among meron and skyrmion crystals in a centrosymmetric magnet
• Pyrochlore Oxide Superconductor Cd2Re2O7 Revisited
• Excitonic Instability and Pseudogap Formation in Nodal Line Semimetal ZrSiS
• A systematic study of stacked square nets: from Dirac fermions to material realizations
• Local orthorhombic lattice distortions in the paramagnetic tetragonal phase of superconducting NaFe${}_{1-x}$Ni${}_x$As
• NaAlSi: a self-doped semimetallic superconductor with free electrons and covalent holes
• Excitonic instability and unconventional pairing in the nodal-line materials ZrSiS and ZrSiSe
• Superconductivity in the Topological Nodal-line Semimetal NaAlSi
• Extremely large magnetoresistance in the hourglass Dirac loop chain metal β-ReO${}_2$
• High-Mobility Carriers Induced by Chemical Doping in the Candidate Nodal-Line Semimetal CaAgP
• Field-induced multiple metal-insulator crossovers of correlated Dirac electrons of perovskite CaIrO${}_3$
• Unusual Resistive Transitions in the Nodal-Line Semimetallic Superconductor NaAlSi
• Pseudogap Formation in the Nodal-Line Semimetal NaAlGe