Massless collective excitations in frustrated multiband superconductors
Keita Kobayashi, Masahiko Machida, Yukihiro Ota, Franco Nori
DOI 10.1103/PhysRevB.88.224516 · Physical Review B
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Abstract
We study collective excitations in three- and four-band superconductors with interband frustration, which causes neither 0 nor π interband phases in the superconducting state. Using a low-energy spin Hamiltonian originating from a multiband tight-binding model, we find that mass reduction of a Leggett mode occurs in a wide parameter region of this four-band system. As a limiting case, we have a massless Leggett mode. This massless mode is related to the fact that the mean-field energy does not depend on a relative phase of superconducting order parameters. In other words, we find a link of the massless mode with a degeneracy between a time-reversal-symmetry-breaking state (neither 0 nor π phases) and a time-reversal-symmetric state (either 0 or π phases). Therefore, the mass of collective modes characterizes well the time-reversal symmetry in frustrated multiband superconductors.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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