Incipient loop-current order in the underdoped cuprate superconductors

Abstract

There is growing experimental evidence that indicates discrete symmetry-breaking-like time-reversal (T), parity (P), and C4 lattice rotation in the pseudogap state of underdoped copper-oxide-based (cuprate) superconductors. The discrete symmetry breaking manifests a true phase transition to an ordered state. A detailed thermodynamic understanding of these orders can answer various puzzles related to the nature of the transition at the pseudogap temperature T*. In this work, we investigate the thermodynamic signature of T−P symmetry breaking considering superconductivity (SC) and bond-density wave (BDW) as two primary orders. The BDW can generate both modulating charge and current densities. This framework takes into account an intricate competition between the ubiquitous charge density wave and SC, which is prominent in various cuprates in the underdoped regime. We demonstrate that within the mean-field approach of competing BDW and SC orders, a T−P breaking ground state of coexisting BDW and SC can be stabilized, provided the BDW itself breaks T−P. But this ground state ceases to occur at higher temperatures. However, we show that fluctuations in SC and BDW can bring about the emergence of an unusual translational symmetry preserving order due to a preemptive phase transition by spontaneously breaking T−P at a higher temperature before the primary orders set in. We refer to this order as magnetoelectric loop current (MELC) order. We present the possible nature of the phase transition for this incipient MELC order and discuss some experimental relevance.

Source-reported materials — not catalogue approval

Similar papers