Abstract
Unconventional symmetry-breaking phenomena due to nontrivial order parameters attract increasing attention in strongly correlated electron systems. Here, we predict theoretically the occurrence of nanoscale spontaneous spin-current, called the spin loop-current (sLC) order, as a promising origin of the pseudogap and electronic nematicity in cuprates. We reveal that the sLC is driven by the odd-parity electron-hole condensation that are mediated by transverse spin fluctuations around the pseudogap temperature $T^*$. At the same temperature, odd-parity magnon pair condensation occurs. The sLC order is "hidden" in that neither internal magnetic field nor charge density modulation is induced, whereas the predicted sLC with finite wavenumber naturally gives the Fermi arc structure. In addition, the fluctuations of sLC order work as attractive pairing interaction between adjacent hot spots, which enlarges the d-wave superconducting transition temperature $T_c$. The sLC state will be a key ingredient in understanding the pseudogap, electronic nematicity as well as superconductivity in cuprates and other strongly correlated metals.
Highlights
Various unconventional symmetry-breaking phenomena, such as violations of rotational and parity symmetries, have been discovered in many strongly correlated metals recently
TCDW ∼ 200 K, a stripe charge-channel density wave emerges at finite wave vector q ≈ (π /2, 0) in many compounds [1,2,3,4], which produces the Fermi arc structure and causes a reduction in the density of states (DOS)
It was revealed that the formation of triplet odd-parity electron-hole pairs is mediated by spin fluctuations, and the spontaneous sLC is established at T = TsLC
Summary
Various unconventional symmetry-breaking phenomena, such as violations of rotational and parity symmetries, have been discovered in many strongly correlated metals recently This fact strongly indicates the emergence of exotic density-wave orders, which are totally different from usual spin/charge-density waves. A spin-fluctuation mechanism [22,23] predicts the ferro (q = 0) d-wave BO state at T ∗ and stripe [q ≈ (π /2, 0)] BO at TCDW The former order explains the experimental nematic transition [10,13]. We discover the emergence of “hidden symmetry breaking” accompanied by finite spin current at qsLC ≈ (π /2, π /2) This sLC order originates from the spinflipping magnon-exchange process, called the Aslamazov-. The present study can explain the sLC order based on a simple Hubbard model with on-site U , without assuming the wave vector qsLC
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