Emergence of mesoscale quantum phase transitions in a ferromagnet

Abstract

Mesoscale patterns as observed, e.g., in ferromagnets, ferroelectrics, superconductors, mono-molecular films, or block-copolymers, reflect spatial variations of a pertinent order parameter at length- and time-scales that may be described classically. This raises the question for the relevance of mesoscale patterns near zero temperature phase transitions, also known as quantum phase transitions (QPTs). Here we report the magnetic susceptibility of LiHoF${}_4$ -- a dipolar Ising ferromagnet -- near a well-understood transverse-field quantum critical point (TF-QCP). When tilting the magnetic field away from the hard axis such that the Ising symmetry is always broken, a line of well-defined phase transitions emerges from the TF-QCP characteristic of an additional symmetry breaking, in stark contrast to a crossover expected microscopically. We show that a continuous suppression of ferromagnetic domains, representing a breaking of translation symmetry on mesoscopic scales in an environment of broken magnetic Ising symmetry on microscopic scales, is in excellent qualitative and quantitative agreement with the field- and temperature dependence of the susceptibility and the magnetic phase diagram of LiHoF${}_4$ under tilted field. This identifies a new type of phase transition that may be referred to as mesocale quantum criticality, which emanates from the text-book example of a microscopic ferromagnetic TF-QCP. Our results establish the surroundings of QPTs as a regime of mesoscale pattern formation, where non-analytical quantum dynamics and materials properties without classical analogue may be expected.

References in corpus (10)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• "Deconfined" quantum critical points
• Bose-Einstein Condensation in Magnetic Insulators
• Formation of a topological non-Fermi liquid in MnSi
• Perturbative Quantum Monte Carlo Study of LiHoF4 in a Transverse Magnetic Field
• The ferromagnetic transition and domain structure in LiHoF4
• Magnetic properties of the itinerant ferromagnet LaCrGe3 under pressure studied by 139La NMR
• Limits to magnetic quantum criticality from nuclear spins
• Absence of Domain Wall Roughening in a Transverse Field Ising Model with Long-Range Interactions
• Compact susceptometer for studies under transverse field geometries at very low temperatures

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• LiHoF4 as a spin-half non-standard quantum Ising system
• Emergent electric field induced by dissipative sliding dynamics of domain walls in a Weyl magnet
• Paramagnetic electron-nuclear spin entanglement in HoCo2Zn20
• Magnetostatic modes and criticality in quantum-Ising materials
• Ising Supercriticality and Universal Magnetocalorics in Spiral Antiferromagnet Nd${}_3$BWO${}_9$
• Quantum Supercritical Crossover with Dynamical Singularity