Probing time-reversal symmetry breaking at microwave frequencies

Abstract

Motivated by experiments carried out in the near infrared using zero-loop-area Sagnac interferometers, we explore electromagnetic signatures of time-reversal symmetry breaking (TRSB) at microwave frequencies, using as a prototypical example a semiclassical conductor in a magnetic field. TRSB is generically accompanied by a skew-symmetric term in the electrodynamic response tensors (permittivity, conductivity, surface impedance), imparting a nonreciprocal phase shift to left- and right-circularly polarized electromagnetic waves reflected from the surface of such a material. We show that TRSB manifests as a difference in the surface reactance experienced by circularly polarized waves, and can be detected using a doubly degenerate resonator mode, such as the TE${}_{111}$ mode of a cylindrical cavity. In addition to the frequency splitting induced by TRSB we show that, when interrogated by circularly polarized microwaves, the forward and reverse transmission responses of such a resonator break reciprocity, providing a crucial signature that distinguishes true Faraday effects (i.e., circular birefringence) from non-TRSB effects such as linear birefringence. In the limit that the sample is larger than the spot size (i.e., larger than the diameter of the microwave cavity) we show that the TRSB resonator has sensitivity to polar Kerr angle comparable to that of the zero-loop-area Sagnac, and should provide complementary insights into unconventional superconductors such as UPt${}_3$ and Sr${}_2$RuO${}_4$ that have been observed to spontaneously break time-reversal symmetry.

12 pages, 6 figures

References in corpus (9)

• High Resolution Polar Kerr Effect Measurements of Sr2RuO4: Evidence for Broken Time Reversal Symmetry in the Superconducting State
• Polar Kerr Effect Measurements of YBa2Cu3O6+x: Evidence for Broken Symmetry Near the Pseudogap Temperature
• The Order Parameter for the Superconducting Phases of UPt${}_3$
• Observation of broken time-reversal symmetry in the heavy fermion superconductor UPt${}_3$
• Modified Sagnac interferometer for high-sensitivity magneto-optic measurements atcryogenic temperatures
• Superconducting state of Sr${}_2$RuO${}_4$ in the presence of longer-range Coulomb interactions
• Spontaneous time-reversal symmetry breaking by disorder in superconductors
• Modified Martin-Puplett interferometer for magneto-optical Kerr effect measurements at sub-THz frequencies
• Microwave Hall measurements using a circularly polarized dielectric cavity

Cited by in corpus (1)

• Microwave resonator for measuring time-reversal symmetry breaking at cryogenic temperatures