307 citations · 1.7k across the 55 of their papers we have counts for
16 papers · 1 filter
Site-Order Optimization in the Density Matrix Renormalization Group via Multi-Site Rearrangement
Ryo Watanabe, Toshiya Hikihara, Hiroshi Ueda
In the approaches based on matrix-product states (MPSs), such as the density-matrix renormalization group (DMRG) method, the ordering of the sites crucially affects the computation…
Tree-Graph Based Construction of Quantum Spin Models with Exact Ground State
Toshiya Hikihara
We propose a protocol to generate an antiferromagnetic S=1/2 Heisenberg model with the exact ground state based on a tree graph. The generated model has a correspondence with a tre…
Improving accuracy of tree-tensor network approach by optimization of network structure
Toshiya Hikihara, Hiroshi Ueda, Kouichi Okunishi +2
Numerical methods based on tensor networks have been extensively explored in the research of quantum many-body systems in recent years. It has been recognized that the ability of t…
Visualization of Entanglement Geometry by Structural Optimization of Tree Tensor Network
Toshiya Hikihara, Hiroshi Ueda, Kouichi Okunishi +2
In tensor-network analysis of quantum many-body systems, it is of crucial importance to employ a tensor network with a spatial structure suitable for representing the state of inte…
Automatic structural optimization of tree tensor networks
Toshiya Hikihara, Hiroshi Ueda, Kouichi Okunishi +2
Tree tensor network (TTN) provides an essential theoretical framework for the practical simulation of quantum many-body systems, where the network structure defined by the connecti…
Exact ground states of frustrated quantum spin systems consisting of spin-dimer units
Toshiya Hikihara, Takashi Tonegawa, Kiyomi Okamoto +1
We study frustrated quantum spin systems consisting of dimers of spin-1/2 spins. We derive several models that have the exact ground state of the form of the direct product of dime…
Sine-square deformation of free fermion systems in one and higher dimensions
Isao Maruyama, Hosho Katsura, Toshiya Hikihara
We study free fermion systems with the sine-square deformation (SSD), in which the energy scale of local Hamiltonians is modified according to the scaling function f(x)=sin^2[π(x-1…
Connecting distant ends of one-dimensional critical systems by a sine-square deformation
Toshiya Hikihara, Tomotoshi Nishino
We study the one-dimensional quantum critical spin systems with the sine-square deformation, in which the energy scale in the Hamiltonian at the position is modified by the fun…
Magnetic phase diagram of the spin-1/2 antiferromagnetic zigzag ladder
T. Hikihara, T. Momoi, A. Furusaki +1
We study the one-dimensional spin-1/2 Heisenberg model with antiferromagnetic nearest-neighbor J_1 and next-nearest-neighbor J_2 exchange couplings in magnetic field h. With varyin…
Phase diagram of the frustrated spin ladder
Toshiya Hikihara, Oleg A. Starykh
We re-visit the phase diagram of the frustrated spin-1/2 ladder with two competing inter-chain antiferromagnetic exchanges, rung coupling J_\perp and diagonal coupling J_\times. We…
Ground-State Phase Diagram of Frustrated Anisotropic Quantum Spin Chains
T. Hikihara, M. Kaburagi, H. Kawamura
Recent studies on the frustrated quantum spin chains with easy-plane anisotropy are reviewed. We are particularly interested in novel "chiral" phases characterized by the spontaneo…
Ground-State Phase Diagram of Frustrated Antiferromagnetic S=1 Chain with Uniaxial Single-Ion-Type Anisotropy
Toshiya Hikihara
The ground-state phase diagram of a frustrated S=1 Heisenberg spin chain with uniaxial single-ion-type anisotropy is studied using the infinite-system density-matrix renormalizatio…
Chiral ordered phases in a frustrated S=1 chain with uniaxial single-ion-type anisotropy
Toshiya Hikihara
The ground-state phase transitions of a frustrated S=1 Heisenberg chain with the uniaxial single-ion-type anisotropy and the frustrating next-nearest-neighbor coupling are studied.…
Numerical renormalization-group study of spin correlations in one-dimensional random spin chains
T. Hikihara, A. Furusaki, M. Sigrist
We calculate the ground-state two-spin correlation functions of spin-1/2 quantum Heisenberg chains with random exchange couplings using the real-space renormalization group scheme.…
Fixed Point of the Finite System DMRG
H. Takasaki, T. Hikihara, T. Nishino
The density matrix renormalization group (DMRG) is a numerical method that optimizes a variational state expressed by a tensor product. We show that the ground state is not fully o…
Correlation amplitude for S=1/2 XXZ spin chain in the critical region
T. Hikihara, A. Furusaki
The density-matrix renormalization-group technique is used to calculate the spin correlation functions <S^x_jS^x_k> and <S^z_jS^z_k> of the one-dimensional S=1/2 XXZ model in the g…