Topological semimetal-to-insulator phase transition between noncollinear and noncoplanar multiple-Q states on a square-to-triangular lattice

Abstract

Noncollinear and noncoplanar magnetic orders lead to unusual electronic structures and transport properties. We here investigate two types of multiple-Q magnetically ordered states and a topological phase transition between them in two dimensions. One is a coplanar but noncollinear double-Q state on a square lattice, which is a semimetal accommodating massless Dirac electrons. The other is a noncoplanar triple-Q state on a triangular lattice, which is a Chern insulator showing the quantum anomalous Hall effect. We discuss the peculiar electronic structures in these two multiple-Q states in a unified way on the basis of the Kondo lattice model, which suggests a quantum phase transition between the two states in a continuous change of lattice geometry between the square and triangular lattices. We systematically examine the possibility of such a transition by using the mean-field approximation for the ground state of the periodic Anderson model. After clarifying the parameter region in which the double-Q (triple-Q) state is stabilized on the square (triangular) lattice, we show that a continuous topological phase transition indeed takes place between the double-Q Dirac semimetal and the triple-Q Chern insulator on the square-to-triangular lattice. The nature of the transition is discussed by the topologically-protected edge states as well as the bulk magnetic and electronic properties. The results indicate that unusual critical phenomena may occur at finite temperature related with multiple-Q chiral spin-liquid states.

10 pages, 9 figures

References in corpus (12)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• Quantum Spin Hall Effect in Inverted Type II Semiconductors
• Quantum Spin Hall Effect and Enhanced Magnetic Response by Spin-Orbit Coupling
• Scalar spin chirality and quantum Hall effect on a triangular lattice
• Novel magnetic orderings in the kagome Kondo-lattice model
• Noncoplanar magnetic ordering driven by itinerant electrons on the pyrochlore lattice
• The Kondo Lattice Model in Infinite Dimensions II. Static Susceptibilities and Phase Diagram
• Quantum Anomalous Hall Effect in Kagome Ice
• Charge order in Kondo lattice systems