Evidence of Chiral Order in the Charge-Ordered Phase of SuperconductingLa1.875Ba0.125Cuo4Single Crystals Using Pol

Abstract

High resolution polar Kerr effect measurements were performed on La1.875Ba0.125CuO4 single crystals revealing that a finite Kerr signal is measured below an onset temperature TK that coincides with the charge ordering transition temperature TCO. We further show that the sign of the Kerr signal cannot be trained with the magnetic field, is found to be the same on opposite sides of the same crystal, and is odd with respect to strain in the diagonal direction of the unit cell. These observations are consistent with a chiral "gyrotropic" order above Tc for La1.875Ba0.125CuO4; similarities to other cuprates suggest that it is a universal property in the pseudogap regime.

Numerical exploration of spontaneous broken symmetries in multiorbital Hubbard models

“…29 Here the sign of the Kerr signal cannot be trained by magnetic fields, suggesting a connection to striped phases 30 or chiral charge orders. [31][32][33][34] 38 This order breaks time-reversal symmetry but preserves translational lattice symmetry with a q = 0 ordering vector.…”

Polar Kerr effect from a time-reversal symmetry breaking unidirectional charge density wave

“…Most strikingly, our results in the ordered phase ( = 10 meV) with a purely real refractive index nicely reproduce the correct order of magnitude of the polar Kerr angle in all three cuprates YBa 2 Cu 3 O 6+x [12], Pb 0.55 Bi 1.5 Sr 1.6 La 0.4 CuO 6+δ [9], and La 1.875 Ba 0.125 CuO 4 [11], which are all of the order of θ K ≈ 1 μrad. Nevertheless, as pointed out recently by several authors [13,64,65], the full complexity of the Kerr effect measurements of the cuprates is more intricate than previously thought. Importantly, the effect cannot be controlled by an applied magnetic field and does not change sign on opposite surfaces of the sample [13].…”

“…Nevertheless, as pointed out recently by several authors [13,64,65], the full complexity of the Kerr effect measurements of the cuprates is more intricate than previously thought. Importantly, the effect cannot be controlled by an applied magnetic field and does not change sign on opposite surfaces of the sample [13]. Although our current effective two-dimensional one-band description is unable to account for these aspects, it is a step forward towards a truly quantitative understanding of the Kerr effect in the cuprates and calls for a more microscopic model including oxygen orbitals and the effect of three dimensionality.…”

“…In particular, x-ray and neutron scattering experiments as well as scanning tunneling microscopy (STM) have found the breaking of the lattice symmetry from C 4 down to C 2 below the pseudogap temperature T * in several cuprate compounds [5][6][7]10]. In addition, recent findings of the polar Kerr effect [9,[11][12][13], and the intraunit cell magnetic order [14] point towards breaking of time-reversal or mirror symmetries in the underdoped cuprates. Furthermore, direct indications in favor of the static incommensurate charge-density-wave (CDW) order with momenta Q x = (2Q,0) and/or Q y = (0,2Q) were found by x-ray measurements [15][16][17][18], the nuclear magnetic resonance technique [19][20][21], and in experiments on the sound velocity in a magnetic field [22].…”

Coupling of magnetic orders inLa2CuO4+x

“…Additional evidence for broken symmetry in the PG region comes from high-precision polar Kerr effect (PKE) measurements of cuprates [6,24,25]. The effect signals TRSB but demonstrates unusual characteristics ascribed to a chiral order [25].…”