Optical tests for broken time-reversal symmetry in the cuprate superconductors
Optical measurements have been made on YBa[sub 2]Cu[sub 3]O[sub 7] and Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] to search for both spontaneous Faraday rotation (in transmission) and spontaneous Kerr rotation (reflection). The observation of these magneto-optical effects near Tc would be a clear indication that the superconductivity in the cuprate superconductors can be explained by a theory which predicts broken time-reversal (T) symmetry. In particular, the [open quotes]any on[close quotes] model of these materials predicts that T symmetry will be broken spontaneously as the material is cooled. The magneto-optical effects are expected to be quite small compared to the birefringence of the material. A method has been developed that uses a fiber-optic Sagnac interferometer to search for the magneto-optic signal. Incident upon the samples are two counter-propagating circularly polarized beams, whose electric fields have opposite time dependence. The interferometer detects Faraday or Kerr rotation by measuring the difference in phase between these beams after they have interacted with the sample. Because it is immune to birefringence in the sample, this method is superior to simply analyzing the polarization state of a single beam. Transmission experiments at 1060 nm wavelength were done with a modified fiber-optic gyroscope (a type of Sagnac interferometer). The nonreciprocal phase shift observed in the cuprates was less than the sensitivity (2 [mu]rad). A 670 nm interferometer was constructed to look for these effects in the visible portion of the spectrum, where other researchers have witnessed unusual polarization effects.Both reflection and transmission measurements at this wavelength indicate there are no magneto-optic effects to a sensitivity of 5 [mu]rad. This technique has been applied successfully to study ferromagnetic phase transitions in films of EuO and Gd.
- Research Organization:
- Stanford Univ., CA (United States)
- OSTI ID:
- 6988327
- Country of Publication:
- United States
- Language:
- English
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75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
ANYONS
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
CUPRATES
DIELECTRIC PROPERTIES
ELECTRICAL PROPERTIES
ELEMENTS
EUROPIUM COMPOUNDS
EUROPIUM OXIDES
FARADAY EFFECT
GADOLINIUM
HIGH-TC SUPERCONDUCTORS
INTERMETALLIC COMPOUNDS
KERR EFFECT
MAGNETO-OPTICAL EFFECTS
METALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
QUASI PARTICLES
RARE EARTH COMPOUNDS
RARE EARTHS
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
SYMMETRY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES