Abstract
We investigate spinon band topology and engineering from the interplay between long-ranged magnetic order and fractionalized spinons, as well as Zeeman coupling under external magnetic fields, in honeycomb lattice magnets. The synergism of N\'eel order and magnetic fields could reconstruct the spinon bands and drive a topological phase transition from the coexisting phase of long-ranged order and chiral spin liquid with semion topological order to the conventional magnetic order. Our prediction can be immediately tested through thermal Hall transport measurements among the honeycomb lattice magnets that are tuned to be proximate to the quantum critical point. Our theory should also shed light on the critical behavior of honeycomb Kitaev materials with emergent Majorana fermion bands. We suggest a possible relevance to the spin-1/2 honeycomb spin liquid candidate material In$_3$Cu$_2$VO$_9$.
Highlights
Since the concept of a resonated valence bond state was introduced by Anderson [1], great progress has been made to understand the quantum spin liquid (QSL), an exotic quantum state of matter characterized by fractionalized spin excitations and emergent gauge structures [2,3,4]
For the chiral spin liquid (CSL), we identify a topological phase transition with increasing magnetic field, we find a quantized thermal Hall effect in the coexisting phase and a nontrivial thermal Hall response in the confining ordered phase near the quantum critical point
The interplay between the conventional long-ranged magnetic order and Zeeman coupling is transmitted into the spinon bands and influences their topology
Summary
Since the concept of a resonated valence bond state was introduced by Anderson [1], great progress has been made to understand the quantum spin liquid (QSL), an exotic quantum state of matter characterized by fractionalized spin excitations and emergent gauge structures [2,3,4]. A prominent example is the Kitaev spin-1/2 model on a honeycomb lattice, where geometrical frustration is absent [5] Instead, it is the presence of bond-dependent Kitaev interactions that induces strong quantum fluctuations and frustrates spin orders. It is generally believed that the ground state of the nearest-neighbor Heisenberg model on the honeycomb lattice is a conventional antiferromagnetic Néel order, while turning on the secondneighbor interaction would melt this long-range order and drive the system into a quantum disordered phase. [21] further considered the third-neighbor exchange J3 and the scalar spin chirality term Jχ , and singled out a parameter window of the CSL proximate to the conventional Néel order They formulated a gauge theory to study the transition from the CSL to another proximate-confining tetrahedral state. The situation that we considered here would apply to the relevant quantum materials with multiple competing phases, where the interplay among conventional ordered states, fractionalized elementary excitations in QSLs and Zeeman coupling together drive the topological phase transition and result in nontrivial thermal Hall signatures
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