arXiv subjects

J. Fink

Publications and source records attributed to J. Fink.

At least 73 records · Page 4Linked to original sources

arXiv2006

A reevaluation of the coupling to a bosonic mode of the charge carriers in (Bi,Pb)$_2$Sr$_2$CaCu$_2$O$_{8+δ} $ at the antinodal point

Angle-resolved photoemission spectroscopy (ARPES) is used to study the spectral function of the optimally doped high-T$_c$ superconductor (Bi,Pb)$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ in the vicinity of the antinodal point in the superconducting state. Using a parameterized self-energy function, it was possible to describe both the coherent and the incoherent spectral weight of the bonding and the antibonding band. The renormalization effects can be assigned to a very strong coupling to the magnetic resonance mode and at higher energies to a bandwidth renormalization by a factor of two, probably caused by a coupling to a continuum. The present reevaluation of the ARPES data allows to come to a more reliable determination of the value of the coupling strength of the charge carriers to the mode. The experimental results for the dressing of the charge carriers are compared to theoretical models.

cond-mat.supr-con↗

arXiv2005

"Kinks", Nodal Bilayer Splitting and Interband Scattering in YBCO

We apply the new-generation ARPES methodology to the most widely studied cuprate superconductor YBCO. Considering the nodal direction, we found noticeable renormalization effects known as "kinks" both in the quasiparticle dispersion and scattering rate, the bilayer splitting and evidence for strong interband scattering -- all the characteristic features of the nodal quasiparticles detected earlier in BSCCO. The typical energy scale and the doping dependence of the "kinks" clearly point to their intimate relation with the spin-1 resonance seen in the neutron scattering experiments. Our findings strongly suggest a universality of the electron dynamics in the bilayer superconducting cuprates and a dominating role of the spin-fluctuations in the formation of the quasiparticles along the nodal direction.

cond-mat.supr-con↗

arXiv2005

Constituents of the "kink" in high-Tc cuprates

Applying the Kramers-Kronig consistent procedure, developed earlier, we investigate in details the formation of the quasiparticle spectrum along the nodal direction of high-Tc cuprates. The heavily discussed "70 meV kink" on the renormalized dispersion exhibits a strong temperature and doping dependence when purified from structural effects. This dependence is well understood in terms of fermionic and bosonic constituents of the self-energy. The latter follows the evolution of the spin-fluctuation spectrum, emerging below T* and sharpening below Tc, and is the main responsible for the formation of the kink in question.

cond-mat.supr-con↗

arXiv2005

Life of the nodal quasiparticles in Bi-2212 as seen by ARPES

While the pronounced doping dependence of the quasiparticle spectral weight in the antinodal region of the superconducting cuprates, as seen by ARPES, unambiguously points to the magnetic origin of the strong electron-boson coupling there, the nature of the electron scattering in the nodal direction remained unclear. Here we present a short review of our recent detailed investigations of the nodal direction of Bi-2212. Our findings prove the existence of well defined quasiparticles even in the pseudogap state and show that the essential part of the quasiparticle scattering rate, which appears on top of Auger-like electron-electron interaction, also implies a magnetic origin.

cond-mat.supr-con↗

arXiv2005

Effect of Zn and Ni impurities on the quasiparticle renormalization in Bi-2212

The Cu substitution by Zn and Ni impurities and its influence on the mass renormalization effects in angle resolved photoelectron spectra (ARPES) of Bi-2212 is addressed. We show that the nonmagnetic Zn atoms have much stronger effect both in nodal and antinodal parts of the Brillouin zone than magnetic Ni. The observed changes are consistent with the behaviour of the spin resonance mode as seen by inelastic neutron scattering in YBCO. This strongly suggests that the "peak-dip-hump" and the "kink" in ARPES on the one side and neutron resonance on the other are closely related features.

cond-mat.supr-con↗

arXiv2005

Parity of the Pairing Bosons in a High-Temperature Superconductor

We report the observation of a novel effect in the bilayer Pb-Bi2212 high-TC superconductor by means of angle-resolved photoemission with circularly polarized excitation. Different scattering rates, determined as a function of energy separately for the bonding and antibonding copper-oxygen bands, strongly imply that the dominating scattering channel is odd with respect to layer exchange within a bilayer. This is inconsistent with a phonon-mediated scattering and favours the participation of the odd collective spin excitations in the scattering mechanism in near-nodal regions of the k-space, suggesting a magnetic nature of the pairing mediator.

cond-mat.supr-con↗

arXiv2004

Change of quasiparticle dispersion in crossing T_c in the underdoped cuprates

One of the most remarkable properties of the high-temperature superconductors is a pseudogap regime appearing in the underdoped cuprates above the superconducting transition temperature T_c. The pseudogap continously develops out of the superconducting gap. In this paper, we demonstrate by means of a detailed comparison between theory and experiment that the characteristic change of quasiparticle dispersion in crossing T_c in the underdoped cuprates can be understood as being due to phase fluctuations of the superconducting order parameter. In particular, we show that within a phase fluctuation model the characteristic back-turning BCS bands disappear above T_c whereas the gap remains open. Furthermore, the pseudogap rather has a U-shape instead of the characteristic V-shape of a d_{x^2-y^2}-wave pairing symmetry and starts closing from the nodal k=(pi/2,pi/2) directions, whereas it rather fills in at the anti-nodal k=(pi,0) regions, yielding further support to the phase fluctuation scenario.

cond-mat.supr-con↗

arXiv2004

Bare electron dispersion from photoemission experiments

Performing an in-depth analysis of the photoemission spectra along the nodal direction of the high temperature superconductor Bi-2212 we have developed a procedure to determine the underlying electronic structure and established a precise relation of the measured quantities to the real and imaginary parts of the self-energy of electronic excitations. The self-consistency of the procedure with respect to the Kramers-Kronig transformation allows us to draw conclusions on the applicability of the spectral function analysis and on the existence of well defined quasiparticles along the nodal direction even for the underdoped Bi-2212 in the pseudogap state.

cond-mat.str-el↗

arXiv2004

Doping dependence of the many-body effects along the nodal direction in the high-Tc cuprate (Bi,Pb)_2Sr_2CaCu_2O_8

Angle-resolved photoemission spectroscopy (ARPES) is used to study the doping dependence of the lifetime and the mass renormalization of the low energy excitations in the high-Tc cuprate (Bi,Pb)_2Sr_2CaCu_2O_8 along the zone diagonal. We find a linear energy de-pendence of the scattering rate for the underdoped samples and a quadratic energy depend-ence in the overdoped case. The mass enhancement of the quasiparticles due to the many body effects at the Fermi energy is found to be in the order of 2 and the renormalization extends over a large energy range for both the normal and the superconducting state. The much discussed kink in the dispersion around 70 meV is interpreted as a small additional effect at low temperatures.

cond-mat.supr-con↗

arXiv2004

Origin of the shadow Fermi surface in Bi-based cuprates

We used angle-resolved photoemission spectroscopy to study the shadow Fermi surface in one layer Bi2Sr1.6La0.4CuO6+delta and two layer (Bi,Pb)2Sr2CaCu2O8+delta. We find the shadow band to have the same peakwidth and dispersion as the main band. In addition, the shadow band/main band intensity ratio is found to be binding energy independent. Consequently, it is concluded that the shadow bands in Bi-based HTSC do not originate from antiferromagnetic interactions but have a structural origin.

cond-mat.str-el↗

arXiv2004

Evidence for CuO conducting band splitting in the nodal direction of Bi-2212

Using angle-resolved photoemission spectroscopy with ultimate momentum resolution we have explicitly resolved the bilayer splitting in the nodal direction of Bi-2212. The splitting is observed in a wide doping range and, within the experimental uncertainty, its size does not depend on doping. The value of splitting derived from the experiment is in good agreement with that from band structure calculations which implies the absence of any electronic confinement to single planes within bilayers of Bi-2212. Other consequences of this finding are also discussed.

cond-mat.supr-con↗

arXiv2004

Transition from a Tomonaga-Luttinger liquid to a Fermi liquid in potassium intercalated bundles of single wall carbon nanotubes

We report on the first direct observation of a transition from a Tomonaga-Luttinger liquid to a Fermi liquid behavior in potassium intercalated mats of single wall carbon nanotubes (SWCNT). Using high resolution photoemission spectroscopy an analysis of the spectral shape near the Fermi level reveals a Tomonaga-Luttinger liquid power law scaling in the density of states for the pristine sample and for low dopant concentration. As soon as the doping is high enough to fill bands of the semiconducting tubes a distinct transition to a bundle of only metallic SWCNT with a scaling behavior of a normal Fermi liquid occurs. This can be explained by a strong screening of the Coulomb interaction between charge carriers and/or an increased hopping matrix element between the tubes.

cond-mat.mtrl-sci↗

arXiv2004

Manifestation of the magnetic resonance mode in the nodal quasiparticle lifetime in superconducting cuprates

Studying the nodal quasiparticles in superconducting cuprates by photoemission with highly improved momentum resolution, we show that a new "kink" feature in the scattering rate is a key to uncover the nature of electron correlations in these compounds. Our data provide evidence that the main doping independent contribution to the scattering can be well understood in terms of the conventional Fermi liquid model, while the additional doping dependent contribution has a magnetic origin. This sheds doubt on applicability of a phonon-mediated pairing mechanism to high temperature superconductors.

cond-mat.supr-con↗

arXiv2004

Angle-resolved photoemission using the circularly polarized light in Pb-Bi2212

In a recent preprint Campuzano et al.(cond-mat/0309402), have questioned the validity of our ARPES results (cond-mat/0305179) contradicting the interpretation of earlier photoemission experiments in terms of the time-reversal symmetry breaking in Bi2212. Here we highlight the principal results of our study and refute all the criticism.

cond-mat.supr-con↗

arXiv2004

Time-reversal symmetry breaking versus superstructure

One of the mysteries of modern condenced-matter physics is the nature of the pseudogap state of the superconducting cuprates. Kaminski et al.1 claimed to have observed signatures of time-reversal symmetry breaking in the pseudogap regime in underdoped Bi2Sr2CaCu2O8+d (Bi2212). Here we argue that the observed dichroism is due to the 5x1 superstructure replica of the electronic bands and therefore cannot be considered as evidence for the spontaneous time-reversal symmetry breaking in cuprates.

cond-mat.supr-con↗

arXiv2003

Circular dichroism and bilayer splitting in the normal state of underdoped (Pb,Bi)$_2$Sr$_2$(Ca$_x$Y$_{1-x}$)Cu$_2$O$_{8+δ}$ and overdoped (Pb,Bi)$_2$Sr$_2$CaCu$_2$O$_{8+δ}$

We report an ARPES investigation of the circular dichroism in the first Brillouin zone (BZ) of under- and overdoped Pb-Bi2212 samples. We show that the dichroism has opposite signs for bonding and antibonding components of the bilayer-split CuO-band and is antisymmetric with respect to reflections in both mirror planes parallel to the c-axis. Using this property of the energy and momentum intensity distributions we prove the existence of the bilayer splitting in the normal state of the underdoped compound and compare its value with the splitting in overdoped sample. In agreement with previous studies the magnitude of the interlayer coupling does not depend significantly on doping. We also discuss possible origins of the observed dichroism.

cond-mat.supr-con↗

arXiv2003

Circular dichroism in angle-resolved photoemission spectra of under- and overdoped Pb-Bi2212

We use angle-resolved photoemission with circularly polarized excitation to demonstrate that in the 5x1 superstructure-free Pb-Bi2212 material there are no signatures of time-reversal symmetry breaking in the sense of the criteria developed earlier (Kaminski et al. Nature {\bf 416}, 610 (2002)). In addition to the existing technique, we suggest and apply an independent experimental approach to prove the absence of the effect in the studied compounds. The dichroic signal retains reflection antisymmetry as a function of temperature and doping and in all mirror planes, precisely defined by the experimental dispersion at low energies. The obtained results demonstrate that the signatures of time-reversal symmetry violation in pristine Bi2212, as determined by ARPES, are not a universal feature of all cuprate superconductors.

cond-mat.supr-con↗

arXiv2003

Doping dependence of the mass enhancement in (Pb,Bi)_2 Sr_2 Ca Cu_2 O_8 at the antinodal point in the superconducting and normal state

Angle-resolved photoemission spectroscopy (ARPES) is used to study the mass renormalization of the charge carriers in the high-T_c superconductor (Pb,Bi)_2Sr_2CaCu_2O_8 in the vicinity of the (pi,0) point in the superconducting and the normal state. Using matrix element effects at different photon energies and due to a high momentum and energy resolution the bonding and the antibonding bands could be separated in the whole dopant range. A huge anisotropic coupling to a bosonic collective mode is observed below T_c for both bands in particular for the underdoped case. Above T_c, the more isotropic coupling to a continuum or a mode at much higher energy is significantly weaker.

cond-mat.supr-con↗