Charge-density-wave origin of the dip-hump structure in tunnel spectra of the BSCCO superconductor (original) (raw)
Related papers
Charge-Density-Wave Origin of Dip-Hump Structures in the Tunnel Spectra of Bi2Sr2CaCu2O8+delta
Acta Physica Polonica A, 2007
We calculated the differential conductance G as the function of the bias voltage V across the tunnel junction between a normal metal or a conventional superconductor and an inhomogeneous superconductor with charge density waves. Spatial averaging over random domains with varying superconducting and normal state properties was carried out. For high-Tc oxides, irregularly distorted charge density wave patterns with spatially scattered values of various parameters were earlier shown to manifest themselves in a great body of experimental data. The results of calculation were applied to explain the well-known dip-hump structure in the G(V) dependence for Bi2Sr2CaCu2O8+δ and other cuprates.
Physica C-superconductivity and Its Applications, 2008
We have calculated quasiparticle current–voltage characteristics J(V) for non-symmetric CDWS–I–N tunnel junctions between a partially gapped charge-density wave (CDW) s-wave superconductor and a normal metal (I stands for an insulator), as well as for symmetric CDWS–I–CDWS junctions. Relevant parameters of CDWS are considered spatially inhomogeneous in accordance with experimental data for various cuprates, especially Bi2Sr2CaCu2O8+δ (BSCCO). The calculated dependences G(V) = dJ(V)/dV demonstrate conspicuous dip-hump structures (DHSs) at low temperatures, T, and pseudogap shallow well at high T > Tc above the critical temperature. In CDWS–I–N junctions, DHSs were shown to be observed for either one or both voltage polarities, depending on the CDW order parameter phase. Similar symmetric DHSs were found for CDWS–I–CDWS junctions. J(V) for break-junctions made of BSCCO were measured. Qualitative agreement was reached between our theoretically calculated and experimental G(V) dependences.
Effect of charge density waves on the tunnel spectra of the Bi 2 Sr 2 CaCu 2 O 8+δ superconductor
Physics of The Solid State, 2007
The differential tunnel conductance G S of the junction between a normal metal and a superconductor with a charge density wave (CDW) is calculated as a function of the voltage V across the junction. The results are averaged over the spread of superconducting and CDW energy gaps in the nanoscale-inhomogeneous superconductor. It is shown that, if both order parameters are nonzero, a dip-hump structure is formed beyond the superconducting gap of G S ( V ). If the phase of the CDW order parameter is not equal to π /2, a dip-hump structure will appear solely or mainly for one sign of the bias polarity. The results agree with the experimental data for Bi 2 Sr 2 CaCu 2 O 8 + δ and other high-temperature oxides
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 .
Effect of charge density waves on the tunnel spectra of the Bi 2 Sr 2 CaCu 2</
Phys Solid State, 2007
The differential tunnel conductance G S of the junction between a normal metal and a superconductor with a charge density wave (CDW) is calculated as a function of the voltage V across the junction. The results are averaged over the spread of superconducting and CDW energy gaps in the nanoscale-inhomogeneous superconductor. It is shown that, if both order parameters are nonzero, a dip-hump structure is formed beyond the superconducting gap of G S ( V). If the phase of the CDW order parameter is not equal to π/2, a dip-hump structure will appear solely or mainly for one sign of the bias polarity. The results agree with the experimental data for Bi2Sr2CaCu2O8+δ and other high-temperature oxides
Physica C, 2014
Quasiparticle differential current–voltage characteristics (CVCs) GðVÞ of non-symmetric tunnel junctions between d-wave superconductors with charge-density waves (CDWs) and normal metals were calculated. The dependences GðVÞ were shown to have aV-like form at small voltagesV and low temperatures, and to be asymmetric at larger V owing to the presence of CDW peak in either of theV-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 one, the PDHS evolves into a pseudogap depression. The results agree well with the scanning tunneling microscopy data for i2Sr2CaCu2O8+d and YBa2Cu3O7d. The results differ substantially from those obtained earlier for CDWs-wave superconductors.
Journal of Physics-condensed Matter, 2008
Temperature, T , variations of the tunnel conductance G(V ) were calculated for junctions between a normal metal and a spatially inhomogeneous superconductor with a dielectric gap on the nested sections of the Fermi surface or between two such superconductors. The dielectric gapping was considered to be a consequence of the charge density wave (CDW) appearance due to the electron-phonon (for a Peierls insulator) or a Coulomb (for an excitonic insulator) interactions. Spatial averaging was carried out over random domains with varying parameters of the CDW superconductor (CDWS). The calculated tunnel spectra demonstrate a smooth transformation from asymmetric patterns with a pronounced dip-hump structure at low T into those with a pseudogap depletion of the electron densities of states at higher T in the vicinity or above the actual critical temperatures of the superconducting transition for any of the CDWS domains. Thus, it is demonstrated that both the dip-hump structure and pseudogapping are manifestations of the same phenomenon. A possible CDW-induced asymmetry of the background contribution to G(V ) is also touched upon. The results explain the peculiar features of G(V ) for Bi 2 Sr 2 CaCu 2 O 8+δ and other related high-T c cuprates.
Charge-density-wave features in tunnel spectra of high-Tc superconductors
2009
Abstract. Tunnel conductances G (V)= dJ/dV (V), where J (V) is the quasiparticle current and V is the voltage, have been calculated for nonsymmetric (CDWS-IN) and symmetric (CDWS-ICDWS) tunnel junctions (N, I, and CDWS stand for a normal metal, insulator, and electronically inhomogeneous CDW superconductor, respectively). The CDWS inhomogeneity was shown to be responsible for the appearance of smooth but conspicuous dip-hump structures (DHSs) in G (V) at T≪ Tc.
Low Temperature Physics, 2008
Tunnel conductance G V () for break-junctions made of as-grown single-crystal Bi 2 Sr 2 CaCu 2 O 8+d samples with T c »-86 89 K was measured and clear-cut dip-hump structures (DHSs) were found in the range 80 120-mV of the bias voltage V. The theory of tunneling in symmetric junctions between inhomogeneous charge-density-wave (CDW) superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel current-voltage characteristics and properly describes experimental results.
2008
Tunnel conductance G V ( ) for break-junctions made of as-grown single-crystal Bi2Sr2CaCu2O8+ samples with Tc 86 89 K was measured and clear-cut dip-hump structures (DHSs) were found in the range 80 120 mV of the bias voltage V . The theory of tunneling in symmetric junctions between inhomogeneous charge-density-wave (CDW) superconductors, considered in the framework of the s-pairing model, has been developed. CDWs have been shown to be responsible for the appearance of the DHS in the tunnel current-voltage characteristics and properly describes experimental results.