Commensurate and incommensurate spin-density waves in heavy electron systems

Abstract

The nesting of the Fermi surfaces of an electron and a hole pocket separated by a nesting vector Q and the interaction between electrons gives rise to itinerant antiferromagnetism. The order can gradually be suppressed by mismatching the nesting and a quantum critical point (QCP) is obtained as the Néel temperature tends to zero. The transfer of pairs of electrons between the pockets can lead to a superconducting dome above the QCP (if Q is commensurate with the lattice, i.e. equal to G/2). If the vector Q is not commensurate with the lattice there are eight possible phases: commensurate and incommensurate spin and charge density waves and four superconductivity phases, two of them with modulated order parameter of the FFLO type. The renormalization group equations are studied and numerically integrated. A re-entrant SDW phase (either commensurate or incommensurate) is obtained as a function of the mismatch of the Fermi surfaces and the magnitude of |Q − G/2|.

The Magnetic Genome of Two-Dimensional van der Waals Materials

“…Future materials in this class are likely to host a high proportion of magnetic atoms separated by a vdW gap and the theory should account for possibly complex magnetic sublattices. We note that spin density waves in metallic 2D vdW magnets might induce a periodic charge modulation, particularly at Fermi surfaces prone to nesting behavior. ,, As seen on the example of Fe 5 GeTe 2 , critical behavior and scaling analysis should yield exponents consistent with 3D magnetic behavior for small vdW gaps (Table ).…”

“…We note that spin density waves in metallic 2D vdW magnets might induce a periodic charge modulation, particularly at Fermi surfaces prone to nesting behavior. 18 , 344 , 345 As seen on the example of Fe 5 GeTe 2 , critical behavior and scaling analysis should yield exponents consistent with 3D magnetic behavior for small vdW gaps ( Table 7 ).…”