Related papers: Higgs Oscillations in time-resolved Optical Conduc…
Time-resolved terahertz time-domain spectroscopy (THz-TDS) is an ideal tool for probing photoinduced nonequilibrium metallic and superconducting states. Here, we focus on the interpretation of the two-dimensional response function…
Higgs mode in superconducting materials describes slowly-decaying oscillations of the order parameter amplitude. We demonstrate that in magnetic superconductors with built-in spin-splitting field Higgs mode is strongly coupled to the spin…
A theory is presented for a nonequilibrium phase transition in the two-dimensional Hubbard model coupled to electrodes. Nonequilibrium magnetic and superconducting phase diagram is determined by the Keldysh method, where the electron…
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 s-wave superconductors was observed is…
We investigate the interplay between gap oscillations and damping in the dynamics of superconductors taken out of equilibrium by strong optical pulses with sub-gap Terahertz frequencies. A semi-phenomenological formalism is developed to…
We study the dynamics of the longitudinal collective mode in an unconventional superconductor. For concreteness, we assume that the superconductor is described by a $d$-wave order parameter with $d_{x^2-y^2}$ symmetry. After the…
Observing the ``Higgs" or amplitude mode in superconductors has been a central challenge in condensed matter physics. Moreover, arriving at a theoretical understanding of this mode and how it is accessible in, say, conductivity experiments…
Higgs modes emerge in superconductors as collective excitations of the order parameter amplitude when periodically driven by electromagnetic radiation. In this work, we develop a Floquet approach to study Higgs modes in superconductors…
Collective excitation modes are a characteristic feature of symmetry-broken phases of matter. For example, superconductors exhibit an amplitude Higgs mode and a phase mode, which are the radial and angular excitations in the Mexican-hat…
This work investigates amplitude-dependent nonlinear corrections to the dissipative conductivity in superconductors, using the Keldysh--Usadel theory of nonequilibrium superconductivity, which captures the nonequilibrium dynamics of both…
Employing the Schwinger-Keldysh formalism, we formulate an effective field theory for s-wave superconducting phase transition, where the dynamical variables consist of electromagnetic gauge field and complex scalar order parameter.…
We review recent work on the theory for pump/probe photoemission spectroscopy of electron-phonon mediated superconductors in both the normal and the superconducting states. We describe the formal developments that allow one to solve the…
In most superconductors, optical excitations require impurity scattering or the presence of multiple bands. This is because in clean single-band superconductors, the combination of particle-hole and inversion symmetries prevents…
Non-equilibrium phase transitions are studied theoretically for the two-dimensional Hubbard model subject to bias voltages from the electrodes coupled to the system. By combining the fluctuation exchange approximation with the Keldysh…
Using a nonequilibrium implementation of the Lanczos-based exact diagonalisation technique we study the possibility of the light-induced superconducting phase coherence in a solid state system after an ultrafast optical excitation. In…
A hydrodynamic theory of transport in quantum mechanically phase-disordered superconductors is possible when supercurrent relaxation can be treated as a slow process. We obtain general results for the frequency-dependent conductivity of…
Ultrafast responses of BCS superconductor Nb1-xTixN films in a nonadiabatic excitation regime were investigated by using terahertz (THz) pump-THz probe spectroscopy. After an instantaneous excitation with the monocycle THz pump pulse, a…
The theory of time-dependent quantum transport addresses the question: How do electrons flow through a junction under the influence of an external perturbation as time goes by? In this paper, we invert this question and search for a…
Development of ultrafast lasers and non-linear optical techniques over the last two decades provides tools to access real-time dynamics of low energy excitations in superconductors. For example, time-resolved THz spectroscopy and time- and…
Symmetry-breaking phase transitions are central to our understanding of states of matter. When a continuous symmetry is spontaneously broken, new excitations appear that are tied to fluctuations of the order parameter. In superconductors…