arXiv subjects

J. Zaanen

Publications and source records attributed to J. Zaanen.

At least 55 records · Page 3Linked to original sources

arXiv2007

The SU(2) Gauge Theory of the Substantially Doped Mott-Insulator: the phase separated d+s superconductor

We reformulate the mean-field theory associated with the SU(2) gauge theory of spin-charge separation in doped Mott-insulators of Wen and Lee so that it can deal with the regime of substantial carrier density. We find that it describes remarkably accurately phase separation tendencies. Moreover, for elegant reasons the theory insists that the superconducting state should have a d+s orderparameter with an s-wave component growing in the overdoped regime. This appears to be consistent with both Raman- and tunneling measurements in cuprate superconductors.

cond-mat.str-el↗

arXiv2007

Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances

Motivated by heavy ion collision experiments, we study the hydrodynamic properties of non-Abelian systems. These issues arise in condensed matter physics in the context of transport of spins in the presence of spin orbit coupling: the Pauli Hamiltonian governing the leading relativistic corrections in condensed matter systems can be rewritten in a language of SU(2) covariant derivatives, where the role of the non-Abelian gauge fields is taken by the physical electromagnetic fields. Taking a similar perspective as Jackiw and coworkers, we show that non-abelian hydrodynamical currents can be factored in a non-coherent 'classical' part, and a coherent part requiring macroscopic non-abelian quantum entanglement. Non-abelian flow being thus a much richer affair than familiar hydrodynamics, permits us to classify the various spin transport phenomena in in condensed matter physics in a unifying framework.In semiconductor spintronics, the absence of hydrodynamics is well known, but in our formulation it is directly associated with the fact that non-abelian currents are only covariantly conserved.We analyze the quantum mechanical single particle currents of relevance to mesoscopic transport with as highlight the Aharonov-Casher effect, where we demonstrate that the non-abelian transport structure renders it much more fragile than its abelian counterpart, the Aharonov-Bohm effect. We subsequently focus on spin flows protected by order parameters, of which the spin-spiral magnets and the spin superfluids are important examples. The surprising bonus is that the presence of an order parameter, being single-valued, restores hydrodynamics. We demonstrate a new effect: the trapping of electrical line charge, being the 'fixed frame' non-Abelian analogue of the familiar magnetic flux trapping by superconductors.

cond-mat.str-el↗

arXiv2006

The hierarchy of multiple many-body interaction scales in high-temperature superconductors

To date, angle-resolved photoemission spectroscopy has been successful in identifying energy scales of the many-body interactions in correlated materials, focused on binding energies of up to a few hundred meV below the Fermi energy. Here, at higher energy scale, we present improved experimental data from four families of high-Tc superconductors over a wide doping range that reveal a hierarchy of many-body interaction scales focused on: the low energy anomaly ("kink") of 0.03-0.09eV, a high energy anomaly of 0.3-0.5eV, and an anomalous enhancement of the width of the LDA-based CuO2 band extending to energies of ~ 2 eV. Besides their universal behavior over the families, we find that all of these three dispersion anomalies also show clear doping dependence over the doping range presented.

cond-mat.supr-con↗

arXiv2006

Calculation of overdamped c-axis charge dynamics and the coupling to polar phonons in cuprate superconductors

In our recent paper we presented empirical evidences suggesting that electrons in cuprate superconductors are strongly coupled to unscreened c-axis polar phonons. In the overdoped regime the c-axis metallizes and we present here simple theoretical arguments demonstrating that the observed effect of the metallic c-axis screening on the polar electron-phonon coupling is consistent with a strongly overdamped c-axis charge dynamics in the optimally doped system, becoming less dissipative in the overdoped regime.

cond-mat.supr-con↗

arXiv2006

The quantum smectic as a dislocation Higgs phase

The theory describing quantum-smectics in 2+1 dimensions, based on topological quantum melting is presented. This is governed by a dislocation condensate characterized by an ordering of Burger's vector and this `dual shear superconductor' manifests itself in the form of a novel spectrum of phonon-like modes.

cond-mat.str-el↗

arXiv2006

Observing the fluctuating stripes in high Tc superconductors

Resting on the gauge theory of topological quantum melting in 2+1 dimensions, we predict that a superconductor characterized by crystalline correlations on a length scale large compared to the lattice carries a new collective mode: the massive shear photon. This mode is visible in the electrodynamic response and the ramification of our theory is that electron energy loss spectroscopy can be employed to prove or disprove the existence of dynamical stripes in cuprate superconductors.

cond-mat.str-el↗

arXiv2006

Doping dependence of the coupling of electrons to bosonic modes in the single-layer high-temperature Bi2Sr2CuO6 superconductor

A recent highlight in the study of high-Tc superconductors is the observation of band renormalization / self-energy effects on the quasiparticles. This is seen in the form of kinks in the quasiparticle dispersions as measured by photoemission and interpreted as signatures of collective bosonic modes coupling to the electrons. Here we compare for the first time the self-energies in an optimally doped and strongly overdoped, non-superconducting single-layer Bi-cuprate (Bi2Sr2CuO6). Besides the appearance of a strong overall weakening, we also find that weight of the self-energy in the overdoped system shifts to higher energies. We present evidence that this is related to a change in the coupling to c-axis phonons due to the rapid change of the c-axis screening in this doping range.

cond-mat.supr-con↗

arXiv2005

Vortex duality: watching the dual side with order propagators

In condensed matter physics, Kramers-Wannier duality implies that the state disordered by quantum fluctuations or temperature actually corresponds with an ordered state formed from the topological excitations of the 'original' ordered state. At first sight it might appear to be impossible to observe this dual order using means associated with the original order. Although true for Ising models, we consider in this paper the well known vortex duality, in particular in the quantum interpretation in 2+1D where it is associated with the quantum phase transition from a superfluid to a Bose Mott insulator. Here, the disordered Mott insulating state is at the same time a dual superconductor corresponding with a Bose condensate of vortices. We present a simple formalism making it possible to compute the velocity propagator associated with the superfluid in terms of the degrees of freedom of the dual theory. The Mott insulator is characterized by a doublet of massive modes and we demonstrate that one of these modes is nothing else than the longitudinal photon (gauged second sound) of the dual superconductor. For increasing momenta, the system rediscovers the original order, and the effect on the velocity correlator is that the longitudinal photon looses its pole strength. The quantum critical regime as probed by the velocity correlator is most interesting. We demonstrate that at infinite wavelength the continua of critical modes associated with second sound and the dual longitudinal photon are indistinguishable. However, at finite momenta they behave differently, tracking the weight reshuffling found in the quasiparticle spectrum of the disorder state closely.

cond-mat.str-el↗

arXiv2005

Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites

A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu-O bonds) directions in momentum space, generally assumed to be linked to the "d-wave" symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite "Fermi arcs". This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity or by invoking orders which are natural competitors of d-wave superconductors. Here we report experimental evidence that a very similar pseudogap state with a nodal-antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state.

cond-mat.str-el↗

arXiv2005

Topological kinematic constraints: quantum dislocations and the glide principle

Topological defects play an important role in physics of elastic media and liquid crystals. Their kinematics is determined by constraints of topological origin. An example is the glide motion of dislocations which has been extensively studied by metallurgists. In a recent theoretical study dealing with quantum dualities associated with the quantum melting of solids it was argued that these kinematic constraints play a central role in defining the quantum field theories of relevance to the description of quantum liquid crystalline states of the nematic type. This forms the motivation to analyze more thoroughly the climb constraints underlying the glide motions. In the setting of continuum field theory the climb constraint is equivalent to the condition that the density of constituent particles is vanishing and we derive a mathematical definition of this constraint which has a universal status. This makes possible to study the kinematics of dislocations in arbitrary space-time dimensions and as an example we analyze the restricted climb associated with edge dislocations in 3+1D. Very generally, it can be shown that the climb constraint is equivalent to the condition that dislocations do not communicate with compressional stresses at long distances. However, the formalism makes possible to address the full non-linear theory of relevance to short distance behaviors where violations of the constraint become possible.

cond-mat.str-el↗

arXiv2004

Quantum criticality and the metal-insulator transition in 2D: a critical test

Using recent insights obtained in heavy fermion physics on the thermodynamic singularity structure associated with quantum phase transitions, we present here an experimental strategy to establish if the zero-temperature transition in the disordered two dimensional gas is a real quantum phase transition. We derive a overcomplete set of scaling laws relating the density and temperature dependence of the chemical potential and the effective mass, which are in principle verifyable by experiment.

cond-mat.str-el↗

arXiv2004

NMR evidence for two-step phase-separation in Nd_{1.85}Ce_{0.15}CuO_{4-delta}

By Cu NMR we studied the spin and charge structure in Nd_{2-x}Ce_{x}CuO_{4-delta}. For x=0.15, starting from a superconducting sample, the low temperature magnetic order in the sample reoxygenated under 1 bar oxygen at 900^0 C, reveals a peculiar modulation of the internal field, indicative for a phase characterized by large charge droplets ('Blob'-phase). By prolonged reoxygenation at 4 bar the blobs brake up and the spin structure changes to that of an ordered antiferromagnet (AF). We conclude that the superconductivity in the n-type systems competes with a genuine type I Mott-insulating state.

cond-mat.str-el↗

arXiv2004

Thermodynamics and quantum criticality in cuprate superconductors

We will present elementary scaling arguments focussed on the thermodynamics in the proximity of the quantum critical point in the cuprate superconductors. Extending the analysis centered on the Grüneisen parameter by Rosch, Si and coworkers to the cuprates, we demonstrate that a combination of specific heat- and chemical potential measurements can reveal the nature of the zero temperature singularity. From the known specific heat data it follows that the effective number of time dimensions has to equal the number of space dimensions, while we find a total of six scaling laws governing the temperature and density dependence of the chemical potential, revealing directly the coupling constant scaling dimension.

cond-mat.supr-con↗

arXiv2003

Geometry and the Hidden Order of Luttinger Liquids: the Universality of Squeezed Space

We present the case that Luttinger liquids are characterized by a form of hidden order which is similar, but distinct in some crucial regards, to the hidden order characterizing spin-1 Heisenberg chains. We construct a string correlator for the Luttinger liquid which is similar to the string correlator constructed by den Nijs and Rommelse for the spin chain. From a geometric prespective on the so-called `squeezed space' construction, we demonstrate that the physics at long wavelength can be reformulated in terms of a $Z_2$ gauge theory. Peculiarly, the normal spin chain lives at infinite gauge coupling where it is characterized by deconfinement. We identify the microscopic conditions required for confinement thereby identifying a novel phase of the spin-chain. We demonstrate that the Luttinger liquid can be approached in the same general framework. The difference from the spin chain is that the gauge sector is critical in the sense that the Luttinger liquid is at the phase boundary where the $Z_2$ local symmetry emerges. We evaluate the string correlator analytically and show that the squeezed space structure is present both for the strongly coupled Hubbard model and the non-interacting fermion gas. These structures are hard-wired in the mathematical structure of bosonization and this becomes obvious by considering string correlators. Numerical results are presented for the string correlator using a non-abelian version of the density matrix renormalization group algorithm, confirming in detail the expectations following from the theory. We conclude with some observations regarding the generalization of bosonization to higher dimensions.

cond-mat.str-el↗

arXiv2003

Duality in 2+1D Quantum Elasticity: superconductivity and Quantum Nematic Order

The generalization of the Nelson-Halperin-Young theory of 2D melting to the dynamical 2+1D quantum case is presented. The bosonic quantum crystal dualizes in superfluids or superconductors exhibiting nematic liquid crystalline orders, corresponding with bose condensates of dislocations exhibiting a dual shear Meissner-Higgs mechanism. The topologically ordered nematic phase suggested by Lammert, Toner and Rokshar finds a simple interpretation in this framework. The ordered nematic is a true quantum phase: the dynamical glide principle interferes with the effect that the phonon spectrum of the crystal re-emerges in the direction orthogonal to the director. Novel insights follow from the duality on the fundamental nature of superfluidity and superconductivity. The superfluid can be viewed as an elastic medium having lost its rigidity against shear stresses. Upon dualizing the electrically charged crystal the electromagnetic Meissner phase is recovered, showing peculiar screening current oscillations when the shear penetration depth becomes larger than the London penetration depth.

cond-mat.supr-con↗

arXiv2003

World Nematic Crystal Model of Gravity Explaining the Absence of Torsion

Assuming that at small distances space-time is equivalent to an elastic medium which is isotropic in space and time directions, we demonstrate that the quantum nematic liquid arising from this crystal by spontaneous proliferation of dislocations corresponds with a medium which is merely carrying curvature rigidity. This medium is at large distances indistinguishable from Einstein's spacetime of general relativity. It does not support torsion and possesses string-like curvature sources which in spacetime form world surfaces.

cond-mat.stat-mech↗

arXiv2003

Powerlaw optical conductivity with a constant phase angle in high Tc superconductors

In certain materials with strong electron correlations a quantum phase transition (QPT) at zero temperature can occur, in the proximity of which a quantum critical state of matter has been anticipated. This possibility has recently attracted much attention because the response of such a state of matter is expected to follow universal patterns defined by the quantum mechanical nature of the fluctuations. Forementioned universality manifests itself through power-law behaviours of the response functions. Candidates are found both in heavy fermion systems and in the cuprate high Tc superconductors. Although there are indications for quantum criticality in the cuprate superconductors, the reality and the physical nature of such a QPT are still under debate. Here we identify a universal behaviour of the phase angle of the frequency dependent conductivity that is characteristic of the quantum critical region. We demonstrate that the experimentally measured phase angle agrees precisely with the exponent of the optical conductivity. This points towards a QPT in the cuprates close to optimal doping, although of an unconventional kind.

cond-mat.str-el↗

arXiv2003

World Nematic Crystal Model of Gravity Explaining the Absence of Torsion

We attribute the gravitational interaction between sources of curvature to the world being a crystal which has undergone a quantum phase transition to a nematic phase by a condensation of dislocations. The model explains why spacetime has no observable torsion and predicts the existence of curvature sources in the form of world sheets, albeit with different high-energy properties than those of string models.

gr-qc↗