Classification and characterization of nonequilibrium Higgs modes in unconventional superconductors

@article{Schwarz2020ClassificationAC,
  title={Classification and characterization of nonequilibrium Higgs modes in unconventional superconductors},
  author={Lukas Schwarz and Benedikt Fauseweh and Naoto Tsuji and Nathan Cheng and Nikolaj Bittner and Holger Krull and Mona Berciu and G. S. Uhrig and Andreas P. Schnyder and Stefan Kaiser and Dirk Manske},
  journal={Nature Communications},
  year={2020},
  volume={11}
}
Recent findings of new Higgs modes in unconventional superconductors require a classification and characterization of the modes allowed by nontrivial gap symmetry. Here we develop a theory for a tailored nonequilibrium quantum quench to excite all possible oscillation symmetries of a superconducting condensate. We show that both a finite momentum transfer and quench symmetry allow for an identification of the resulting Higgs oscillations. These serve as a fingerprint for the ground state gap… 
Theory of driven Higgs oscillations and third-harmonic generation in unconventional superconductors
Higgs spectroscopy is a new field in which Higgs modes in nonequilibrium superconductors are analyzed to gain information about the ground state. One experimental setup in which the Higgs mode in
Light quantum control of persisting Higgs modes in iron-based superconductors
TLDR
A tunable coherent amplitude oscillation of the order parameter in Ba(Fe 1− x Co x ) 2 As 2 is observed, suggesting appearance and control of the Higgs mode by light tuning interband interaction, and can be extended to probe many-body entanglement and hidden symmetries in other complex systems.
Phase-resolved Higgs response in superconducting cuprates
TLDR
A universal jump in the phase of the driven Higgs oscillations in cuprate thin films is observed, indicating the presence of a coupled collective mode, as well as a nonvanishing Higgs-like response at high temperatures, suggesting a potential nonzero pairing amplitude above T c.
Spectroscopic signatures of time-reversal symmetry breaking superconductivity
The collective mode spectrum of a symmetry-breaking state, such as a superconductor, provides crucial insight into the nature of the order parameter. In this work, we study two collective modes which
Momentum-resolved analysis of condensate dynamic and Higgs oscillations in quenched superconductors with time-resolved ARPES
Higgs oscillations in nonequilibrium superconductors provide a unique tool to obtain information about the underlying order parameter. Several properties like the absolute value, existence of
Theory of Higgs modes in d -wave superconductors
By applying a microscopic gauge-invariant kinetic theory in $d$-wave superconductors, we analytically derive the energy spectra of the breathing Higgs mode and, in particular, rotating Higgs mode
Proximity-induced collective modes in an unconventional superconductor heterostructure
Unconventional superconductors have been long sought for their potential applications in quantum technologies and devices. A key challenge impeding this effort is the difficulty associated with
Time-resolved optical conductivity and Higgs oscillations in two-band dirty superconductors
Recent studies have emphasized the importance of impurity scattering for the optical Higgs response of superconductors. In the dirty limit, an additional paramagnetic coupling of light to the
Anomalous Higgs oscillations mediated by Berry curvature and quantum metric
Higgs spectroscopy, the study of Higgs bosons of a superconductor, is an emerging field in studying superconductivity. Here we show that the Berry curvature and the quantum metric of bands play a
Higgs mode stabilization by photoinduced long-range interactions in a superconductor
We show that low-lying excitations of a 2D BCS superconductor are significantly altered when coupled to an externally driven cavity, which induces controllable long-range attractive interactions
...
...

References

SHOWING 1-10 OF 78 REFERENCES
Collective modes in pumped unconventional superconductors with competing ground states
Motivated by the recent development of terahertz pump-probe experiments, we investigate the short-time dynamics in superconductors with multiple attractive pairing channels. Studying a single-band
Hybridization of Higgs modes in a bond-density-wave state in cuprates
Recently, several groups have reported observations of collective modes of the charge order present in underdoped cuprates. Motivated by these experiments, we study theoretically the oscillations of
Coupling of Higgs and Leggett modes in non-equilibrium superconductors
TLDR
Using numerical exact simulations, it is shown that optical pump–probe experiments excite both Higgs and Leggett modes out of equilibrium, and that this non-adiabatic excitation process introduces a strong interaction between the collective modes, which is absent in equilibrium.
Infrared Activation of the Higgs Mode by Supercurrent Injection in Superconducting NbN.
TLDR
It is demonstrated that if the dc supercurrent is introduced into the superconductor, the Higgs mode becomes infrared active and is directly observed in the linear optical conductivity measurement.
Theory of Anderson pseudospin resonance with Higgs mode in superconductors
A superconductor illuminated by an ac electric field with frequency $\Omega$ is theoretically found to generate a collective precession of Anderson's pseudospins, and hence a coherent amplitude
Amplitude/Higgs Modes in Condensed Matter Physics
The order parameter and its variations in space and time in many different states in condensed matter physics at low temperatures are described by the complex function Ψ(r, t). These states include
Particle physics in a superconductor
TLDR
Direct observation of the Higgs mode in the conventional superconductor niobium nitride (NbN) excited by intense electric field transients is reported, indicating the existence of superconducting condensates with coherent excited state.
Light-induced collective pseudospin precession resonating with Higgs mode in a superconductor
TLDR
The method presented here paves a way toward nonlinear quantum optics in superconductor with driving the pseudospins collectively and can be potentially extended to exotic superconductors for shedding light on the character of order parameters and their coupling to other degrees of freedom.
Nonlinear optical response of collective modes in multiband superconductors assisted by nonmagnetic impurities
In multiband superconductors, multiple collective modes exist associated with the multiple order parameters. Oscillations of the amplitude and the relative phase of the order parameters are called
Microscopic origin of Cooper pairing in the iron-based superconductor Ba1−xKxFe2As2
Resolving the microscopic pairing mechanism and its experimental identification in unconventional superconductors is among the most vexing problems of contemporary condensed matter physics. We show
...
...