We show that unconventional nematic superconductors with multicomponent order parameter in lattices with three- and sixfold rotational symmetries support a charge-4e vestigial superconducting phase above Tc. The charge-4e state, which is a condensate of four-electron bound states that preserve the rotational symmetry of the lattice, is nearly degenerate with a competing vestigial nematic state, which is nonsuperconducting and breaks the rotational symmetry. This robust result is the consequence of a hidden discrete symmetry in the Ginzburg-Landau theory, which permutes quantities in the gauge sector and in the crystalline sector of the symmetry group. We argue that random strain generally favors the charge-4e state over the nematic phase, as it acts as a random mass to the former but as a random field to the latter. Thus, we propose that two-dimensional inhomogeneous systems displaying nematic superconductivity, such as twisted bilayer graphene, provide a promising platform to realize the elusive charge-4e superconducting phase.
Bibliographical noteFunding Information:
We thank A. Chubukov, P. Orth, J. Schmalian, and J. Venderbos for fruitful discussions. We thank Milan Allan for pointing out the possibility of using Josephson scanning tunneling microscopy to probe charge- superconductivity. R.M.F. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Award No. DE-SC0020045. L. F. was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under Award No. DE-SC0018945. The authors thank the hospitality of KITP during the workshop “Correlations in Moiré Flat Bands,” where this work was initiated. KITP is supported in part by the National Science Foundation under Grant No. NSF PHY-1748958.
© 2021 American Physical Society.
PubMed: MeSH publication types
- Journal Article