Critical drag as a mechanism for resistivity

Understand

A quantum many-body system with a conserved electric charge can have a DC resistivity that is either exactly zero (implying it supports dissipationless current) or nonzero.

• Exactly zero resistivity is related to conservation laws that prevent the current from degrading.
• In this paper, we carefully examine the situations in which such a circumstance can occur.
• We find that exactly zero resistivity requires either continuous translation symmetry, or an internal symmetry that has a certain kind of "mixed anomaly" with the electric charge.