Fermi Surface Reconstruction Research Articles

Band Structure of the Heavily-Electron-Doped FeAs-BasedBa(Fe,​Co)2As2Superconductor Suppresses Antiferromagnetic Correlations

In the heavily-electron-doped regime of the Ba(Fe,Co)2As2 superconductor, three hole bands at the zone center are observed and two of them reach the Fermi level. The larger hole pocket at the zone center is apparently nested with the smaller electron pocket around the zone corner. However, the (pi,0) Fermi surface reconstruction reported for the hole-doped case is absent in the heavily-electron-doped case. This observation shows that the apparent Fermi surface nesting alone is not enough to enhance the antiferromagnetic correlation as well as the superconducting transition temperature.

Possibility of magnetic-field-induced reconstruction of the Fermi surface in underdoped cuprates: Constraints from infrared magneto-optics

We present an analysis of infrared optical and magneto-optical conductivity data for a range of underdoped cuprate superconductors including ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{y}$ and ${\text{La}}_{2\ensuremath{-}x}{\text{Sr}}_{x}{\text{CuO}}_{4}$. In light of recent magneto-oscillation experiments which have been interpreted in terms of Fermi surface reconstruction in magnetic field, we search for far-infrared signatures of field-induced pockets of coherent quasiparticles. Analysis of the conductivity spectra in magnetic field reveals no sign of field-induced Drude-like response, as well as no evidence for modification of the pseudogap. By considering changes of the low-frequency spectral weight, we are able to place limits on the oscillator strength of coherent modes deriving from proposed field-induced pockets in the Fermi surface. In underdoped ${\text{La}}_{2\ensuremath{-}x}{\text{Sr}}_{x}{\text{CuO}}_{4}$ we observe a complete suppression of the superfluid density but no evidence for a coherent contribution to the conductivity. Other limits are established for ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{y}$. We further discuss these results in the context of cuprate systems in which stripe order can account for the observed nodal effects but does not lead to the development of antinodal pockets with long-lived quasiparticles.

Signatures of Fermi surface reconstruction in Raman spectra of underdoped cuprates

We have calculated the Raman ${\text{B}}_{1g}$ and ${\text{B}}_{2g}$ spectra as a function of temperature, as well as doping, for the underdoped cuprates, using a model based on the resonating valence-bond spin liquid. We discuss changes in intensity and peak position brought about by the presence of a pseudogap and the implied Fermi surface reconstruction, which are elements of this model. Signatures of Fermi surface reconstruction are evident as a sharp rise in the doping dependence of the antinodal to nodal peak ratio which occurs below the quantum critical point. The temperature dependence of the ${\text{B}}_{1g}$ polarization can be used to determine if the superconducting gap is limited to the Fermi pocket, as seen in angle-resolved photoemission spectroscopy, or extends beyond. We find that the slope of the linear low-energy ${\text{B}}_{2g}$ spectrum maintains its usual $d$-wave form, but with an effective gap which reflects the gap amplitude projected on the Fermi pocket. Our calculations capture the main qualitative features revealed in the extensive data set available on the ${\text{HgBa}}_{2}{\text{CuO}}_{4+\ensuremath{\delta}}$ (Hg-1201) cuprate.

Nernst and Seebeck Coefficients of the Cuprate SuperconductorYBa2Cu3O6.67: A Study of Fermi Surface Reconstruction

The Seebeck and Nernst coefficients S and nu of the cuprate superconductor YBa{2}Cu{3}O{y} (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28 T. Down to T=9 K, nu becomes independent of field by H approximately 30 T, showing that superconducting fluctuations have become negligible. In this field-induced normal state, S/T and nu/T are both large and negative in the T-->0 limit, with the magnitude and sign of S/T consistent with the small electronlike Fermi surface pocket detected previously by quantum oscillations and the Hall effect. The change of sign in S(T) at T approximately 50 K is remarkably similar to that observed in La2-xBaxCuO4, La{2-x-y}Nd{y}Sr_{x}CuO{4}, and La{2-x-y}Eu{y}Sr{x}CuO{4}, where it is clearly associated with the onset of stripe order. We propose that a similar density-wave mechanism causes the Fermi surface reconstruction in YBCO.

Effect of pseudogap formation on the penetration depth of underdoped high-Tccuprates

The penetration depth is calculated over the entire doping range of the cuprate phase diagram with emphasis on the underdoped regime. Pseudogap formation on approaching the Mott transition, for doping below a quantum critical point, is described within a model based on the resonating valence bond spin liquid which provides an ansatz for the coherent piece of the Green's function. Fermi-surface reconstruction, which is an essential element of the model, has a strong effect on the superfluid density at $T=0$ producing a sharp drop in magnitude but does not change the slope of the linear low-temperature variation. Comparison with recent data on Bi-based cuprates provides validation of the theory and shows that the effects of correlations, captured by Gutzwiller factors, are essential for a qualitative understanding of the data. We find that the Ferrell-Glover-Tinkham sum rule still holds and we compare our results with those for the Fermi arc and the nodal liquid models.

Transport properties in filled skutterudite GdRu4P12

We have investigated the Hall effect in GdRu4P12 for the first time. From the temperature and magnetic field dependences of the Hall effect along with the magnetoresistance, we evaluated the change in carrier density across the antiferromagnetic (AF) transition accompanied by the Fermi surface reconstruction. About one tenth of carriers remain in the AF phase, in contrast with PrRu4P12 where most of the carriers disappear in the ordered phase. The anomalous part of Hall coefficient in GdRu4P12 is smaller than those in the PrRu4P12 and PrFe4P12, which is consistent with the well localized nature of 4f electrons.

Zooming on the quantum critical point in Nd-LSCO

Recent studies of the high-Tc superconductor La1.6-xNd0.4SrxCuO4 (Nd-LSCO) have found a linear-T in-plane resistivity ρab and a logarithmic temperature dependence of the thermopower S/T at a hole doping p=0.24 and a Fermi-surface reconstruction just below p=0.24[1,2]. These are typical signatures of a quantum critical point (QCP). Here we report data on the c-axis resistivity ρc(T) of Nd-LSCO measured as a function of temperature near this QCP, in a magnetic field large enough to entirely suppress superconductivity. Like ρab,ρc shows an upturn at low temperature, a signature of Fermi surface reconstruction caused by stripe order. Tracking the height of the upturn as it decreases with doping enables us to pin down the precise location of the QCP where stripe order ends, at p∗=0.235±0.005. We propose that the temperature Tρ below which the upturn begins marks the onset of the pseudogap phase, found to be roughly twice as high as the stripe-ordering temperature in this material.

Interlayer Josephson coupling in stripe-ordered superconducting cuprates

Motivated by experiments on ${\text{La}}_{2\ensuremath{-}x}{\text{Ba}}_{x}{\text{CuO}}_{4}$ which suggest that stripe order coexists with two-dimensional pairing without interlayer phase coherence, we determine the interlayer Josephson coupling in the presence of stripe order. We employ a mean-field description of bond-centered stripes, with a zero-momentum superconducting condensate and alternating stripe directions pinned by the low-temperature tetragonal (LTT) lattice structure. We show that the Fermi-surface reconstruction arising from strong stripe order can suppress the Josephson coupling between adjacent layers by more than an order of magnitude.

Novel mixed-state thermal transport properties in ultra-clean URu2Si2

The heavy-fermion superconductor URu2Si2 shows an intriguing increase of the thermal conductivity in the mixed-state immediately below the upper critical field Hc2 which is in a sharp contrast to common experience. A brief description of the origin of this behavior is given by focusing on the role of the semi-metallic Fermi surface reconstruction induced by the hidden order phase transition.

Resolution of two apparent paradoxes concerning quantum oscillations in underdoped high-Tcsuperconductors

Recent quantum-oscillation experiments in underdoped high-temperature superconductors seem to imply two paradoxes. The first paradox concerns the apparent nonexistence of the signature of the electron pockets in angle-resolved photoemission spectroscopy (ARPES). The second paradox is a clear signature of a small electron pocket in quantum-oscillation experiments, but no evidence as yet of the corresponding hole pockets of approximately double the frequency of the electron pocket. This hole pockets should be present if the Fermi-surface reconstruction is due to a commensurate density wave, assuming that Luttinger sum rule relating the area of the pockets and the total number of charge carriers holds. Here we provide possible resolutions of these apparent paradoxes from the commensurate $d$-density wave theory. To address the first paradox we have computed the ARPES spectral function subject to correlated disorder, natural to a class of experiments relevant to the materials studied in quantum oscillations. The intensity of the spectral function is significantly reduced for the electron pockets for an intermediate range of disorder correlation length, and typically less than half the hole pocket is visible, mimicking Fermi arcs. Next we show from an exact transfer-matrix calculation of the Shubnikov-de Haas oscillation that the usual disorder affects the electron pocket more significantly than the hole pocket. However, when, in addition, the scattering from vortices in the mixed state is included, it wipes out the frequency corresponding to the hole pocket. Thus, if we are correct, it will be necessary to do measurements at higher magnetic fields and even higher-quality samples to recover the hole-pocket frequency.

Indications for the coexistence of closed orbit and quantum interferometer with the same cross section in the organic metal β′′-(ET)4(H3O)[ Fe(C2O4)3] .C6H4Cl2: persistence of Shubnikov-de Haas oscillations above 30 K

Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) oscillations spectra of the quasi-two dimensional charge transfer salt $\beta$"-(ET)$_4$(H$_3$O)[Fe(C$_2$O$_4$)$_3$]$\cdot$C$_6$H$_4$Cl$_2$ have been investigated in pulsed magnetic fields up to 54 T. The data reveal three basic frequencies F$_a$, F$_b$ and F$_{b - a}$, which can be interpreted on the basis of three compensated closed orbits at low temperature. However a very weak thermal damping of the Fourier component F$_b$, with the highest amplitude, is evidenced for SdH spectra above about 6 K. As a result, magnetoresistance oscillations are observed at temperatures higher than 30 K. This feature, which is not observed for dHvA oscillations, is in line with quantum interference, pointing to a Fermi surface reconstruction in this compound.

Reconstruction of the Fermi surface of HTSC cuprates in a high magnetic field

The effect of a high magnetic field on the electronic structure of HTSC cuprates is considered. The study is performed in the t-t′-t″-J* model, and the high magnetic field effect is taken into account not only as the Zeeman splitting of the one-electron levels, but also in the occupation numbers of the states with different spin projections and in the formation of the spin correlation functions. The field is assumed to be high enough to align all of the spins along the field. As a result, the Fermi surface reconstruction is obtained from four hole pockets about the nodal point (π/2, π/2) in the paramagnetic phase to a large hole pocket about the point (π, π) in the ferromagnetic phase. As the magnetic field strength decreases, a number of quantum phase transitions are revealed; they are manifested in the changed Fermi surface topology. The Fermi surface reconstruction with a decreasing field is qualitatively the same as that with an increasing doping degree in the absence of a magnetic field.

Pressure evolution of a field-induced Fermi surface reconstruction and of the Néel critical field inCeIn3

We report high-pressure skin-depth measurements on the heavy fermion material ${\text{CeIn}}_{3}$ in magnetic fields up to 64 T using a self-resonant tank circuit based on a tunnel diode oscillator. At ambient pressure, an anomaly in the skin depth is seen at 45 T. The field where this anomaly occurs decreases with applied pressure until approximately 1.0 GPa, where it begins to increase before merging with the antiferromagnetic phase boundary. Possible origins for this transport anomaly are explored in terms of a Fermi surface reconstruction. The critical magnetic field at which the N\'eel-ordered phase is suppressed, is also mapped as a function of pressure and extrapolates to the previous ambient-pressure measurements at high magnetic fields and high-pressure measurements at zero magnetic field.

Nernst effect in the electron-doped cuprate superconductors

We calculate the normal-state Nernst signal in the cuprates resulting from a reconstruction of the Fermi surface due to spin-density wave order. An order parameter consistent with the reconstruction of the Fermi surface detected in electron-doped materials is shown to sharply enhance the Nernst signal close to optimal doping. Within a semiclassical treatment, the obtained magnitude and position of the enhanced Nernst signal agrees with Nernst measurements in electron-doped cuprates. Our result is mainly caused by the role of Fermi-surface geometry under influence of a spin-density wave gap. We discuss also possible roles of short-ranged magnetic order in the normal-state Nernst effect and the Fermi-surface reconstruction observed by photoemission spectroscopy.

4f-Derived Fermi Surfaces ofCeRu2(Si1−xGex)2near the Quantum Critical Point: Resonant Soft-X-Ray ARPES Study

Angle-resolved photoelectron spectroscopy in the Ce 3d-->4f excitation region was measured for the paramagnetic state of CeRu2Si2, CeRu2(Si0.82Ge0.18)2, and LaRu2Si2 to investigate the changes of the 4f electron Fermi surfaces around the quantum critical point. While the difference of the Fermi surfaces between CeRu2Si2 and LaRu2Si2 was experimentally confirmed, a strong 4f-electron character was observed in the band structures and the Fermi surfaces of CeRu2Si2 and CeRu2(Si0.82Ge0.18)2, consequently indicating a delocalized nature of the 4f electrons in both compounds. The absence of Fermi surface reconstruction across the critical composition suggests that SDW quantum criticality is more appropriate than local quantum criticality in CeRu2(Si1-xGex)2.

Fermi surface reconstruction inhigh-Tc superconductors

The recent observation of quantum oscillations in underdopedhigh-Tc superconductors, combined with their negative Hall coefficient at low temperature, reveals thatthe Fermi surface of hole-doped cuprates includes a small electron pocket. This stronglysuggests that the large hole Fermi surface characteristic of the overdoped regime undergoesa reconstruction caused by the onset of some order which breaks translational symmetry. Herewe consider the possibility that this order is ‘stripe’ order, a form of combined charge/spinmodulation observed most clearly in materials like Eu-doped and Nd-doped LSCO(La2−xSrxCuO4). In these materials, the onset of stripe order coincides with major changes in transportproperties, providing strong evidence that stripe order is indeed the cause of Fermisurface reconstruction. We identify the critical doping where this reconstructionoccurs and show that the temperature dependence of transport coefficients atthat doping is typical of metals at a quantum critical point. We discuss how thepseudogap phase may be a fluctuating precursor of the stripe-ordered phase.

Fermi surface reconstruction in the Kondo lattice model and the periodic Anderson model

We study the ground state properties of the Kondo lattice model (KLM) and the periodic Anderson model (PAM) in a two-dimensional square lattice with the variational Monte Carlo method. In addition to the conventional second-order antiferromagnetic transition, we find a novel type of quantum phase transition which induces the change of topology of the Fermi surface (Fermi surface reconstruction). The Fermi surface reconstruction is originated from the mechanism of the energy gain and is characteristic both of the KLM and of the PAM. We show the ground state phase diagrams of both models and discuss the relation to the recent experiments which have investigated the change of the Fermi surface.

Band renormalization and Fermi surface reconstruction in iron-based superconductors

Using the fluctuation exchange approximation and a three-orbital model, we study the band renormalization, the Fermi surface reconstruction, and the superconducting pairing symmetry in iron-based superconductors. We find that the interorbital spin fluctuations lead to the strong anisotropic band renormalization and the renormalization is orbital dependent. As a result, the topology of Fermi surface displays distinct variation with doping from the electron type to the hole type, which is consistent with the recent experiments. This shows that the Coulomb interactions will have a strong effect on the band renormalization and the topology of the electron Fermi pocket. In addition, the pairing state mediated by the interorbital spin fluctuation is of an extended $s$-wave symmetry.

Fermi-Surface Reconstruction in the Periodic Anderson Model

We study the ground state properties of a periodic Anderson model in a two-dimensional square lattice with a variational Monte Carlo method. It is shown that there are two different types of quantum phase transition: a conventional antiferromagnetic transition and a Fermi-surface reconstruction that accompanies a change in the topology of the Fermi surface. The former is induced by the simple back-folding of the Fermi surface, while the latter is induced by the localization of f electrons. The mechanism of these transitions and its relationship with the results of recent experiments on the Fermi surface are discussed in detail.

Quantum Phase Transition in the Magnetic-Field-Induced Normal State of Optimum-Doped High-TcCuprate Superconductors at Low Temperatures

A 60 T magnetic field suppresses the superconducting transition temperature T_{c} in La_{2-p}Sr_{p}CuO_{4} to reveal a Hall number anomaly, which develops only at temperatures below zero-field T_{c} and peaks at the exact location of p that maximizes T_{c}. The anomaly bears a striking resemblance to observations in Bi_{2}Sr_{2-x}La_{x}CuO_{6+delta}, suggesting a normal-state phenomenology common to the cuprates that underlies the high-temperature superconducting phase. The peak is ascribed to a Fermi surface reconstruction at a quantum phase transition near optimum doping that is coincident with the collapse of the pseudogap state.