Theory of parametrically amplified electron-phonon superconductivity

Babadi, Mehrtash; Knap, Michael; Martin, Ivar; Refael, Gil; Demler, Eugene

doi:10.1103/physrevb.96.014512

Cited by 153 publications

(134 citation statements)

References 69 publications

(104 reference statements)

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“…On excitation with 0.18-eV pulses (blue curve), a gap appears that is reminiscent of superconductivity 103 . These experiments have motivated theoretical work, both to understand the nature of lattice dynamics arising from nonlinear phonon excitation, and to elucidate the possible origin of the superconducting enhancement 118,119 . The inset of Fig.…”

Section: Phononic Controls Of Quantum Materialsmentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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Q uantum materials are on the ascent. This term embodies a vast portfolio of compounds and phenomena where ramifications of quantum mechanics are demonstrably real. Quantum materials are in the vanguard of contemporary physics in part because these systems afford an exceptional venue to uncover the many roles of symmetry, topology, dimensionality and strong correlations in macroscopic observables. Here we set out to explore the ways and means of creating new states of matter in quantum materials and manipulating their phases via external stimuli. Practical control of these properties is a precondition for exploiting quantum advantages in new photonic, electronic and energy technologies, a task of significant societal impact 1 . We will primarily focus on the following classes of quantum materials: transition metal oxides, Fe-and Cu-based high-T c superconductors, van der Waals semiconductors, topological insulators and Weyl semimetals, and, finally, graphene.The properties of quantum materials are anomalously sensitive to external stimuli. In these systems, interactions associated with spin, charge, lattice and orbital degrees of freedom are commonly on par with the electronic kinetic energy. A rather fragile balance between coexisting and competing ground states can be readily shifted via external stimuli, leading to a raft of quantum phases and transitions between them 2,3 . Furthermore, certain classes of driven quantum states (Fig. 1a and Box 1) are explicit products of coherent interaction between light and matter 4-6 . Alternatively, the properties of quantum materials can be pre-programmed by directly manipulating the electronic wavefunction and the attendant Berry phase that give rise to the anomalous velocity of electrons in a solid [7][8][9] . These complementary avenues of controls mean that investigations no longer need to be reduced to merely observing (in contrast, for example, to astrophysics). Instead, it is now feasible to attain, in a predictable fashion, 'properties on demand' by steering a quantum material towards a desirable ground, metastable or transient state. The past decade has witnessed an explosion in the field of quantum materials, headlined by the predictions and discoveries of novel Landau-symmetry-broken phases in correlated electron systems, topological phases in systems with strong spin-orbit coupling, and ultra-manipulable materials platforms based on two-dimensional van der Waals crystals. Discovering pathways to experimentally realize quantum phases of matter and exert control over their properties is a central goal of modern condensed-matter physics, which holds promise for a new generation of electronic/photonic devices with currently inaccessible and likely unimaginable functionalities. In this Review, we describe emerging strategies for selectively perturbing microscopic interaction parameters, which can be used to transform materials into a desired quantum state. Particular emphasis will be placed on recent successes to tailor electronic interaction parameters through th...

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Section: Phononic Controls Of Quantum Materialsmentioning

confidence: 99%

Towards properties on demand in quantum materials

2017

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“…Initially, the dynamics of local observables at transient and intermediate time scales are controlled by the corresponding integrable theory serving as a metastable attractor for the non-integrable dynamics [4,27,28]. This trapping in a metastable state has been termed prethermalization [27,29] and is expected to exist for several non-integrable models and models close to integrability [4,27,[30][31][32][33][34][35][36][37][38]. In the quasi-particle picture, prethermalization is associated with the initial formation of well-defined excitations [27] which leads to a dephasing of all terms that are not diagonal in quasi-particle modes, i.e.…”

Section: Introductionmentioning

confidence: 99%

Prethermalization and thermalization of a quenched interacting Luttinger liquid

2016

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We study the relaxation dynamics of interacting, one-dimensional fermions with band curvature after a weak quench in the interaction parameter at zero temperature. Our model lies within the class of interacting Luttinger Liquids, where the harmonic Luttinger theory is extended by a weak integrability breaking phonon scattering term. In order to solve for the non-equilibrium time evolution, we use quantum kinetic equations exploiting the resonant but subleading character of the phonon interaction term. The interplay between phonon scattering and the quadratic Luttinger theory leads to the emergence of three distinct spatio-temporal regimes for the fermionic real-space correlation function. It features the crossover from a prequench to a prethermal state, finally evolving towards a thermal state on increasing length and time scales. The characteristic algebraically decaying real-space correlations in the prethermalized regime become modulated by an amplitude, which is decaying in time according to a stretched-exponential as an effect of the interactions. The asymptotic thermalization dynamics is governed by energy transport over large distances from the thermalized to the non-thermalized regions via macroscopic, dynamical slow modes. This is revealed in an algebraic decay of the system's effective temperature. The numerical value of the associated exponent agrees with the dynamical critical exponent of the Kardar-Parisi-Zhang universality class. We also discuss a criterion for the applicability of this theory away from the integrable limit of non-interacting fermions.

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“…This type of modulation of the phonon degrees of freedom has been discussed as a potential origin of the enhancement of superconductivity [11,12,17].…”

Section: Modelmentioning

confidence: 99%

“…In a real system, this detrimental heating effect may potentially be circumvented in two ways: either the heating processes are slow enough so that an enhancement of a long-range order can be observed at least transiently, or the heating is eventually balanced by energy dissipation to the environment, thus leading to the so-called nonequilibrium steady state (NESS). The transient dynamics has been studied by looking at the SC instabilities of the normal phase, in the form of negative eigenvalues of the transient pairing susceptibility [11,17]. While such negative susceptibilities can occur for short times, it is an open question on which time scale the long-range order could evolve in such a situation and whether a potential increase can be fast enough to overcome the heating.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, the resonant excitation of mid-infrared phonon modes has opened a new pathway for manipulating properties such as metallicity [2], magnetism [3], and superconductivity (SC) [4][5][6][7][8][9] and for modifying lattice structures in ways which may not be achievable in equilibrium. Especially, the light-induced SC-like behavior in the optical conductivity for high T c cuprates and doped fullerides [4][5][6][7][8][9] has stimulated several theoretical investigations [10][11][12][13][14][15][16][17][18][19]. So far, two possible scenarios for the enhancement of SC have been discussed in the literature, based on the enhanced pairing interaction out of equilibrium: (i) Under time-periodic driving, the time-averaged Hamiltonian can be modified in such a way that SC is favored [10,14,18], and (ii) the interaction can be effectively enhanced in the driven state by dynamical effects [11][12][13]16].…”

Section: Introductionmentioning

confidence: 99%

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Nonequilibrium steady states and transient dynamics of conventional superconductors under phonon driving

Murakami¹,

Tsuji²,

Eckstein³

et al. 2017

Phys. Rev. B

154

138

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We perform a systematic analysis of the influence of phonon driving on the superconducting Holstein model coupled to heat baths by studying both the transient dynamics and the nonequilibrium steady state (NESS) in the weak and strong electron-phonon coupling regimes. Our study is based on the nonequilibrium dynamical mean-field theory, and for the NESS we present a Floquet formulation adapted to electron-phonon systems. The analysis of the phonon propagator suggests that the effective attractive interaction can be strongly enhanced in a parametric resonant regime because of the Floquet side bands of phonons. While this may be expected to enhance the superconductivity (SC), our fully self-consistent calculations, which include the effects of heating and nonthermal distributions, show that the parametric phonon driving generically results in a suppression or complete melting of the SC order. In the strong coupling regime, the NESS always shows a suppression of the SC gap, the SC order parameter, and the superfluid density as a result of the driving, and this tendency is most prominent at the parametric resonance. Using the real-time nonequilibrium DMFT formalism, we also study the dynamics towards the NESS, which shows that the heating effect dominates the transient dynamics, and SC is weakened by the external driving, in particular at the parametric resonance. In the weak coupling regime, we find that the SC fluctuations above the transition temperature are generally weakened under the driving. The strongest suppression occurs again around the parametric resonances because of the efficient energy absorption.

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Theory of parametrically amplified electron-phonon superconductivity

Cited by 153 publications

References 69 publications

Towards properties on demand in quantum materials

Towards properties on demand in quantum materials

Prethermalization and thermalization of a quenched interacting Luttinger liquid

Nonequilibrium steady states and transient dynamics of conventional superconductors under phonon driving

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