2011/02/09 by A R Schmidt, K Fujita, E-A Kim +6
Materials Science · Physics and Astronomy · #Cooper pair #Delocalized electron #Electronic and Structural Properties of Oxides #Electronic structure #Organic and Molecular Conductors Research #Pairing #Physics of Superconductivity and Magnetism #Pseudogap #Quasiparticle #Superconductivity #Symmetry breaking #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1088/1367-2630/13/6/065014
32 pages with 10 figures
arxiv created 2011/02/09 · openalex publication_date 2011/06/21 · arxiv updated 2015/05/27 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We survey the use of spectroscopic imaging scanning tunneling microscopy (SI-STM) to probe the electronic structure of underdoped cuprates. Two distinct classes of electronic states are observed in both the d-wave superconducting (dSC) and the pseudogap (PG) phases. The first class consists of the dispersive Bogoliubov quasiparticle excitations of a homogeneous d-wave superconductor, existing below a lower energy scale E =Δ 0 . We find that the Bogoliubov quasiparticle interference (QPI) signatures of delocalized Cooper pairing are restricted to a k -space arc, which terminates near the lines connecting k =±(π/ a 0 ,0) to k =±(0,π/ a 0 ). This arc shrinks continuously with decreasing hole density such that Luttinger's theorem could be satisfied if it represents the front side of a hole-pocket that is bounded behind by the lines between k =±(π/ a 0 ,0) and k =±(0,π/ a 0 ). In both phases, the only broken symmetries detected for the | E |<Δ 0 states are those of a d-wave superconductor. The second class of states occurs proximate to the PG energy scale E =Δ 1 . Here the non-dispersive electronic structure breaks the expected 90°-rotational symmetry of electronic structure within each unit cell, at least down to 180°-rotational symmetry. This electronic symmetry breaking was first detected as an electronic inequivalence at the two oxygen sites within each unit cell by using a measure of nematic ( C 2 ) symmetry. Incommensurate non-dispersive conductance modulations, locally breaking both rotational and translational symmetries, coexist with this intra-unit-cell electronic symmetry breaking at E =Δ 1 . Their characteristic wavevector Q is determined by the k -space points where Bogoliubov QPI terminates and therefore changes continuously with doping. The distinct broken electronic symmetry states (intra-unit-cell and finite Q ) coexisting at E ∼Δ 1 are found to be indistinguishable in the dSC and PG phases. The next challenge for SI-STM studies is to determine the relationship of the E ∼Δ 1 broken symmetry electronic states with the PG phase, and with the E <Δ 0 states associated with Cooper pairing.