Local edge modes in doped cuprates with checkerboard polaronic heterogeneity

We study a periodic polaronic system, which exhibits a nanoscale superlattice structure, as a model for hole-doped cuprates with checkerboard-like heterogeneity, as has been observed recently by scanning tunneling microscopy (STM). Within this model, the electronic and phononic excitations are investigated by applying an unrestricted Hartree-Fock and a random phase approximation (RPA) to a multiband Peierls-Hubbard Hamiltonian in two dimensions

Hybridization-driven gap in U3Bi4Ni3: a 209Bi NMR/NQR study

We report 209Bi NMR and NQR measurements on a single crystal of the Kondo insulator U3Bi4Ni3. The 209Bi nuclear spin-lattice relaxation rate ($T_1^{-1}$) shows activated behavior and is well-fit by a spin gap of 220 K. The 209Bi Knight shift (K) exhibits a strong temperature dependence arising from 5f electrons, in which K is negative at high temperatures and increases as the temperature is lowered. Below 50 K, K shows a broad maximum and decreases slightly upon further cooling. Our data provide insight into the evolution of the hyperfine fields in a fully gapped Kondo insulator based on 5f electron hybridization.Comment: 4 pages, 4 figures, submitted to Phys. Rev.

Nuclear magnetic resonance probe head design for precision strain control

We present the design and construction of an NMR probe to investigate single crystals under strain at cryogenic temperatures. The probe head incorporates a piezoelectric-based apparatus from Razorbill Instruments that enables both compressive and tensile strain tuning up to strain values on the order of 0.3% with a precision of 0.001%. As NMR in BaFe2As2 reveals large changes to the electric field gradient and indicates that the strain is homogeneous to within 16% over the volume of the NMR coil

Anomalous NMR Magnetic Shifts in CeCoIn_5

We report ^{115}In and ^{59}Co Nuclear Magnetic Resonance (NMR) measurements in the heavy fermion superconductor CeCoIn_5 above and below T_c. The hyperfine couplings of the In and Co are anisotropic and exhibit dramatic changes below 50K due to changes in the crystal field level populations of the Ce ions. Below T_c the spin susceptibility is suppressed, indicating singlet pairing.Comment: 4 pages, 4 figure

Low Frequency Spin Dynamics in the CeMIn_5 Materials

We measure the spin lattice relaxation of the In(1) nuclei in the CeMIn_5 materials, extract quantitative information about the low energy spin dynamics of the lattice of Ce moments in both CeRhIn_5 and CeCoIn_5, and identify a crossover in the normal state. Above a temperature T* the Ce lattice exhibits "Kondo gas" behavior characterized by local fluctuations of independently screened moments; below T* both systems exhibit a "Kondo liquid" regime in which interactions between the local moments contribute to the spin dynamics. Both the antiferromagnetic and superconducting ground states in these systems emerge from the "Kondo liquid" regime. Our analysis provides strong evidence for quantum criticality in CeCoIn_5.Comment: 4 pages, 3 figure

Coherence Temperature in the Diluted Periodic Anderson Model

The Kondo and Periodic Anderson Model (PAM) are known to provide a microscopic picture of many of the fundamental properties of heavy fermion materials and, more generally, a variety of strong correlation phenomena in $4f$ and $5f$ systems. In this paper, we apply the Determinant Quantum Monte Carlo (DQMC) method to include disorder in the PAM, specifically the removal of a fraction $x$ of the localized orbitals. We determine the evolution of the coherence temperature $T^*$, where the local moments and conduction electrons become entwined in a heavy fermion fluid, with $x$ and with the hybridization $V$ between localized and conduction orbitals. We recover several of the principal observed trends in $T^*$ of doped heavy fermions, and also show that, within this theoretical framework, the calculated Nuclear Magnetic Resonance (NMR) relaxation rate tracks the experimentally measured behavior in pure and doped CeCoIn$_5$. Our results contribute to important issues in the interpretation of local probes of disordered, strongly correlated systems.Comment: 8 pages, 4 figure