Spin-orbit density wave induced hidden topological order in URu2Si2

TL;DR

This paper proposes that a spin-orbit density wave in URu2Si2 explains its hidden order phase, revealing a topologically invariant order parameter that breaks certain symmetries but preserves time-reversal symmetry.

Contribution

It introduces a novel spin-orbit density wave as the hidden order in URu2Si2, supported by ab-initio calculations and effective modeling, highlighting its topological nature.

Findings

Identifies spin-orbit density wave as the hidden order parameter

Shows the order breaks rotational and translational symmetries

Predicts experimental signatures for verification

Abstract

The conventional order parameters in quantum matters are often characterized by 'spontaneous' broken symmetries. However, sometimes the broken symmetries may blend with the invariant symmetries to lead to mysterious emergent phases. The heavy fermion metal URu2Si2 is one such example, where the order parameter responsible for a second-order phase transition at Th = 17.5 K has remained a long-standing mystery. Here we propose via ab-initio calculation and effective model that a novel spin-orbit density wave in the f-states is responsible for the hidden-order phase in URu2Si2. The staggered spin-orbit order 'spontaneous' breaks rotational, and translational symmetries while time-reversal symmetry remains intact. Thus it is immune to pressure, but can be destroyed by magnetic field even at T = 0 K, that means at a quantum critical point. We compute topological index of the order parameter to show that the hidden order is topologically invariant. Finally, some verifiable predictions are presented.