Charge density waves as the origin of dip-hump structures in the differential tunneling conductance of cuprates: The case of d-wave superconductivity

Abstract

Conductance-voltage characteristics (CVCs) for non-symmetric tunnel junctions between d-wave superconductors with charge-density waves (CDWs) and normal metals were calculated. It was shown that they have a V-like form at small voltages V and are asymmetric at larger V owing to the presence of CDW peak in one of the V -branches. The spatial scatter of the dielectric (CDW) order parameter smears the CDW peak into a hump and induces a peak-dip-hump structure (PDHS) typical of CVCs observed for such junctions. At temperatures larger than the superconducting critical temperature, the PDHS evolves into a pseudogap depression. The results agree well with the scanning tunneling microscopy data for Bi 2 Sr 2 CaCu 2 O 8+δ and YBa 2 Cu 3 O 7−δ .

Spatial distribution of superconducting and charge-density-wave order parameters in cuprates and its influence on the quasiparticle tunnel current (Review Article)

“…For d -wave superconductors with s-wave CDWs, we use a theoretical framework suggested earlier [25,27,60,89]. This treatment, in agreement with the experimental data for cuprates, assumes a 2 …”

“…In our previous calculations [60], we showed that taking the spread of only one of SCDW parameters into account (in the case concerned, it was the parameter 0 Σ ) was not sufficient to reproduce the quasiparticle CVCs for nonsymmetric junctions with SCDWs. In this work, we let all SCDW initial parameters …”

“…Both CDWs and the electronic nonhomogeneity should be crucial for tunnel spectroscopy, which studies voltage, V , dependences of the quasiparticle current J and the corresponding conductance ( ) = / G V dJ dV [52][53][54][55][56]. Some time ago we suggested that CDWs have already been detected in the quasiparticle tunnel current-voltage characteristics [30,[57][58][59][60]. Specifically, ( ) G V of junctions (either symmetric or nonsymmetric ones) involving high-c T oxides reveal peak-diphump structures at energies eV much larger than the superconducting gap-edge positions ∆ [25,31,55,61,62].…”

“…Here, > 0 e is the elementary electric charge. There are other scenarios, alternative to our approach (see references in our publications [30,60]), which attempt to explain the existence of those structures. Their main difficulty consists in inevitable conspicuous CDW traces in tunnel junctions with cuprate electrodes; such traces were earlier observed in a number of partially CDW-gapped normal metals and superconductors [63][64][65].…”

Interplay of superconductivity and bosonic coupling in the peak-dip-hump structure of Bi2Sr2CaCu2O8+δ

“…At a single momentum, the peak represents a single quasiparticle pole; but in a momentum-integrated measurement, the peak represents a pileup of many quasiparticle poles at the edge of the superconducting gap. Some simulations have shown that electron-boson coupling could create a momentumintegrated PDHS [19], but other studies have argued that it arises from charge order or the pseudogap [18,20]. Several recent studies have demonstrated the value of integrating across just one dimension of momentum [21][22][23][24].…”