Universal Quantization of Magnetic Susceptibility Jump at Topological Phase Transition

有限温度下高阶拓扑绝缘体的Uhlmann相位

The Uhlmann phase of Higher-Order Topological Insulators at Finite Temperature

基于Uhlmann相位研究高阶拓扑绝缘体的有限温度拓扑性质，通过BBH模型中Uhlmann相位的量子化跳变确定拓扑相变临界温度。

Nonequilibrium occupation number and charge susceptibility of a resonance level close to a dissipative quantum phase transition

Based on the recent paper (Phys. Rev. Lett. 102, 216803, (2009)), we study the nonequilibrium occupation number and charge susceptibility of a resonance level close to a dissipative quantum phase transition of the Kosterlitz-Thouless (KT) type between a de-localized phase for weak dissipation and a localized phase for strong dissipation. The resonance level is coupled to two spinless fermionic baths with a finite bias voltage and an Ohmic bosonic bath representing the dissipative environment. The system is equivalent to an effective anisotropic Kondo model out of equilibrium. Within the nonequ…

Nonlinear Dynamics of Quasiclassical Spin Moment in a Swept Field

Quantum dynamics of anisotropic spin system with large spin moment in a swept magnetic field is theoretically investigated. Magnetic field of this type induces vortex static electrical field, that breaks down the axial symmetry and induces new coherent quantum phenomena: the occurrence of band energy spectrum with continuous spin states, Bloch-type oscillations and interband Zener tunnelling effect. These quantum phenomena display themselves, in particular, in magnetization jumps and susceptibility peaks in the investigated spin system.

Topological contribution to magnetism in the Kane-Mele model: An explicit wave function approach

In our previous publication [S. Ozaki and M. Ogata, Phys. Rev. Research 3, 013058], the quantization of the orbital-Zeeman (OZ) cross term in the magnetic susceptibility, or the cross term of spin Zeeman and orbital effect, was shown for the Kane-Mele model using the expansion around the Dirac points. In the present study, we accurately evaluate the orbital, spin-Zeeman, and OZ cross term of the Kane-Mele model using a recently developed formulation. This formula is written in terms of the explicit Bloch wave functions, and enables us to evaluate each contribution taking account of the integra…

Extremely Weakly Interacting $ΔS_z = 0$ and $ΔS_z = 1$ Excitations and Evidence for Fractional Quantization in a Magnetization Plateau: CeSb

The plateau at 1/3 of the saturation magnetization, $M_s$, in the metamagnet CeSb is accompanied by a state of ferromagnetic layers of spins in an up-up-down sequence. We measured $M$ and the specific heat, $C$, in the plateau, spin wave analyses of which reveal two distinct branches of excitations. Those with $ΔS_z = 1$ as measured by $M$, coexist with a much larger population of $ΔS_z = 0$ excitations measured by $C$ but invisible to $M$. The large density of $ΔS_z = 0$ excitations, their energy gap, and their seeming lack of interaction with $ΔS_z = 1$ excitations suggest an analogy with as…

Renormalization group analysis of the finite 2DXY model with fourfold anisotropy: Application to the magnetic susceptibility of a ferromagnetic ultrathin film

The renormalization group equations describing a finite 2DXY system with fourfold anisotropy are solved in two steps, in order to study the magnetic transition to paramagnetism in an ultrathin film. First, the equations are linearized near the critical coupling $K=J/k_BT=2/π$. An exact solution of the linearized equations confirms that a finite-size Kosterlitz-Thouless (KT) transition occurs in the presence of weak fourfold anisotropy, and that an Ising transition occurs for strong anisotropy. The behaviour of a given system is determined by the product of an anisotropy parameter and the logar…