Spin and current correlation functions in thed-density-wave state of the cuprates

Abstract

We calculate the spin-spin and current-current correlation functions in states exhibiting d x 2 Ϫy 2-density wave ͑DDW͒ order, d x 2 Ϫy 2 superconducting order ͑DSC͒, or both types of orders. The spin-spin correlation functions in a state with both DDW and DSC orders and in a state with DDW order alone, respectively, illuminate the resonant peak seen in the superconducting state of the underdoped cuprates and the corresponding feature seen in the pseudogap regime. The current-current correlation function in a state with both DDW and DSC order evinces a superfluid density with doping dependence, which is consistent with that of the underdoped cuprates. These calculations strengthen the identification of the pseudogap with DDW order and of the underdoped cuprates with a state with both DDW and DSC orders.

Dynamical spin susceptibility and the resonance peak in the pseudogap region of the underdoped cuprate superconductors

“…This qualitative difference between the DDW and the DSC state bears important consequences: for ω > Ω DDW cr , one has Imχ 0 ∼ ω − Ω DDW cr , in contrast to the discontinuous jump of Imχ 0 at Ω DSC cr in the DSC state (this result for the DDW state differs from that in Ref. 4 due to the different Fermi surface topology considered here). This behavior becomes immediately apparent when one plots Imχ 0 in the DDW-state around ω = Ω DDW cr , as shown in the inset of Fig.…”

“…Similar to the superconducting state the lowest critical frequency, Ω (1) cr , reaches zero at η = 0.8(π, π). In contrast, at Ω (3,4,5) cr new scattering channels for interband scattering between the Ω + k and Ω − k bands are opened. These three critical frequencies are degenerate at Q = (π, π), but this degeneracy is lifted for q = Q, as follows immediately from Fig.…”

“…A large number of theoretical scenarios have been proposed to explain the origin of the pseudogap 2,3 . Among these is the d-density wave (DDW) scenario 3 which was suggested to explain some of the salient features of the underdoped cuprates such as the d x 2 −y 2 -wave symmetry of the pseudogap above T c , the anomalous behavior of the superfluid density 4 and of the Hall number 5 , as well as the presence of weak (orbital) antiferromagnetism 6 . The DDW-phase is characterized by circulating bond currents which alternate in space, break time-reversal symmetry and result in an orbital (antiferromagnetically ordered) magnetic moment.…”

Collective modes in thed-density-wave state of the cuprates

“…Consequently, one can not in the case of large |µ| meaningfully talk about the amplitude mode in connection with experiments. But a large value of the chemical potential may not be the case in the underdoped regime of the cuprates, 12 where various kinds of charge inhomogeneities and impurities may actually pin the doped holes. Indeed, there are some indications 18 that µ remains pinned close to zero in these systems.…”

Modulation of the local density of states within thed-density wave theory of the underdoped cuprates

“…While a charge ordered state is a candidate [1], one of us has proposed, and extensively studied, a new order parameter, which results in circulating currents arranged in a staggered pattern(DDW) [2]. Many experiments are consistent with this order parameter, as demonstrated in studies of the superfluid density, the polarized neutron scattering, the Hall number in pulsed 60 T magnetic field, the angle resolved photoemission spectroscopy (ARPES), the lack of specific heat anomaly at the pseudogap temperature, the transition temperature in multilayer cuprates, and the infrared Hall angle measurements [3]. So far the clinching direct experiment, the polarized neutron scattering, has remained suggestive [4] because of the difficulty of detecting weak signals from the small magnetic moments generated by the circulating orbital currents.…”