Masataka Kakoi

We report a 139La-NMR study of polycrystalline samples of multi(n)-layered nickelates, La3Ni2O7−δ (n = 2) and La4Ni3O10−δ (n = 3), at ambient pressure. Measurements of the nuclear magnetic resonance (NMR) spectra and nuclear spin relaxation rate (1/T1) indicate the emergence of a density wave order with a gap below T* ∼ 150 K for La3Ni2O7−δ and ∼130 K for La4Ni3O10−δ. The finite value of 1/T1 below T* indicates metallic ground states with the remaining density of states at the Fermi level (EF) u

To clarify the nature of high-temperature superconductivity in the bilayer nickelate ${\mathrm{La}}_{3}{\mathrm{Ni}}_{2}{\mathrm{O}}_{7}$ under pressure, we investigate, using the density-matrix renormalization group method, the pair correlations in the two-orbital $t\text{\ensuremath{-}}J$ ladder model. While the interchain-intraorbital pair correlations exhibit a slow power-law decay in both orbitals, the interorbital pair correlation also develops strongly enough to be comparable with the int

To clarify the nature of high-temperature superconductivity in the bilayer nickelate La$_3$Ni$_2$O$_7$ under pressure, we investigate, using the density-matrix renormalization group method, the pair correlations in the two-orbital $t$-$J$ ladder model. While the interchain-intraorbital pair correlations exhibit a slow power-law decay in both orbitals, the interorbital pair correlation also develops strongly enough to be comparable with the intraorbital correlations. These intra and interorbital

We investigate, both numerically and analytically, the time evolution of a particle in an initial plane-wave state as it is subject to elastic scattering in a two-dimensional disordered system with Rashba spin-orbit coupling (SOC). In the analytic calculation, we treat the SOC nonperturbatively and the disorder perturbatively using the diffuson and the cooperon. We calculate the time dependence of coherent backscattering as a function of the strength of the SOC. We identify weak and strong SOC r

The $L^2$ localisation landscape of L. Herviou and J. H. Bardarson is a generalisation of the localisation landscape of M. Filoche and S. Mayboroda. We propose a stochastic method to compute the $L^2$ localisation landscape that enables the calculation of landscapes using sparse matrix methods. We also propose an energy filtering of the $L^2$ landscape which can be used to focus on eigenstates with energies in any chosen range of the energy spectrum. We demonstrate the utility of these suggestio

We report a $^{139}$La-NMR study of polycrystalline samples of multi($n$)-layered nickelates, La$_3$Ni$_2$O$_{7-δ}$ ($n=2$) and La$_4$Ni$_3$O$_{10-δ}$ ($n=3$), at ambient pressure. Measurements of the nuclear magnetic resonance (NMR) spectra and nuclear spin relaxation rate ($1/T_1$) indicate the emergence of a density wave order with a gap below $T^*\sim150$ K for La$_3$Ni$_2$O$_{7-δ}$ and $\sim130$ K for La$_4$Ni$_3$O$_{10-δ}$. The finite value of $1/T_1$ below $T^*$ indicates metallic ground

We investigate, both numerically and analytically, the time evolution of a particle in an initial plane wave state as it is subject to elastic scattering in a two-dimensional disordered system with Rashba spin-orbit coupling (SOC). In the analytic calculation, we treat the SOC non-perturbatively, and the disorder perturbatively using the Diffuson and the Cooperon. We calculate the time dependence of coherent backscattering (CBS) as a function of the strength of the SOC. We identify weak and stro

The $L^2$ localisation landscape of L. Herviou and J. H. Bardarson is a generalisation of the localisation landscape of M. Filoche and S. Mayboroda. We propose a stochastic method to compute the $L^2$ localisation landscape that enables the calculation of landscapes using sparse matrix methods. We also propose an energy filtering of the $L^2$ landscape which can be used to focus on eigenstates with energies in any chosen range of the energy spectrum. We demonstrate the utility of these suggestio

We study interference effects in the dynamics of a spin $1/2$ particle propagating in two dimensions in a disordered potential and subject to a generalized spin-orbit coupling. With the particle initially in a spin-polarized plane wave state, in the short-time regime, before the spin and momentum distributions reach their steady states, we observe a transient backscattering peak offset from the exact backscattering direction, coexisting with a coherent backscattering dip. We present an intuitive

We study anisotropic superconductivity in the nearly quarter-filled $α$-$\mathcal{T}_3$ lattice. We analyze an extended Hubbard model with off-site attractive interactions within the mean-field framework and find two distinct chiral $d+id'$-wave superconducting phases characterized by different Chern numbers. We further investigate the superconducting mechanism mediated by spin fluctuations arising from purely repulsive interactions by applying the fluctuation-exchange (FLEX) approximation to th