Collective mode in multicomponent superconductors: the case of FeSe
ORAL
Abstract
Iron-based superconductor FeSe is a striking example of rotational-symmetry breaking multiband superconductivity, as evidenced by its strongly anisotropic superconducting gap structures. The order parameter of this material can be described by a complex admixture of s- and d-wave condensates, originating from electron nematicity [1]. This superconductor has been proposed to break time-reversal symmetry, undergoing a superconducting-superconducting (SC-SC) transition and evolving from a purely nematic state to a mixed state where time-reversal symmetry is also broken, resulting in a peculiar state [2].
Using FeSe as a case study, we investigate the collective excitation spectra of a system in the described SC-SC transition scenario. We explore an effective model of a multicomponent superconductor characterized by an order parameter of the form Δ=Δ1+Δ2 on a single band [3]. We calculate the collective spectra as the system transitions from a purely nematic state to a purely time-reversal symmetry-breaking (TRSB) state. To achieve this, we adopte a linearized pseudospin formalism, coupling the system to an electromagnetic field and solving the equations of motion across the transition to trace the evolution of the three bosonic excitations: two amplitude modes and a relative phase mode.Finally, we compare the theoretical results to experimental measurements on FeSe samples.
[1] P. O. Sprau and A. Kostin and A. Kreisel and A. E. Böhmer and V. Taufour and P. C. Canfield and S. Mukherjee and P. J. Hirschfeld and B. M. Andersen and J. C. Séamus Davis. Discovery of orbital-selective Cooper pairing in FeSe. Science, 357(6346):75-80, 2017
[2] Jian Kang, Andrey V. Chubukov, and Rafael M. Fernandes. Time-reversal symmetry-breaking nematic superconductivity in FeSe. Phys. Rev. B,98:064508, Aug 2018.
[3] Christoph Jurecka and Ewald Schachinger. The phase diagram of an orthorhombic d-wave superconductor. Physica C-superconductivity and Its Applications, 312:304–312, 1999.
Using FeSe as a case study, we investigate the collective excitation spectra of a system in the described SC-SC transition scenario. We explore an effective model of a multicomponent superconductor characterized by an order parameter of the form Δ=Δ1+Δ2 on a single band [3]. We calculate the collective spectra as the system transitions from a purely nematic state to a purely time-reversal symmetry-breaking (TRSB) state. To achieve this, we adopte a linearized pseudospin formalism, coupling the system to an electromagnetic field and solving the equations of motion across the transition to trace the evolution of the three bosonic excitations: two amplitude modes and a relative phase mode.Finally, we compare the theoretical results to experimental measurements on FeSe samples.
[1] P. O. Sprau and A. Kostin and A. Kreisel and A. E. Böhmer and V. Taufour and P. C. Canfield and S. Mukherjee and P. J. Hirschfeld and B. M. Andersen and J. C. Séamus Davis. Discovery of orbital-selective Cooper pairing in FeSe. Science, 357(6346):75-80, 2017
[2] Jian Kang, Andrey V. Chubukov, and Rafael M. Fernandes. Time-reversal symmetry-breaking nematic superconductivity in FeSe. Phys. Rev. B,98:064508, Aug 2018.
[3] Christoph Jurecka and Ewald Schachinger. The phase diagram of an orthorhombic d-wave superconductor. Physica C-superconductivity and Its Applications, 312:304–312, 1999.
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Publication: Planned paper: Observation of Leggett-like collective mode in a multicomponent superconductor FeSe by nonlinear terahertz spectroscopy
Presenters
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Silvia Neri
Max Planck Institute for Solid State Research
Authors
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Silvia Neri
Max Planck Institute for Solid State Research
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Dirk Manske
Max Planck Institute for Solid State Research