Thermodynamics of free and bound magnons in graphene
arXiv:2103.00015 · doi:10.1038/s41567-021-01421-x
Abstract
Symmetry-broken electronic phases support neutral collective excitations. For example, monolayer graphene in the quantum Hall regime hosts a nearly ideal ferromagnetic phase at filling factor that spontaneously breaks spin rotation symmetry. This ferromagnet has been shown to support spin-wave excitations known as magnons which can be generated and detected electrically. While long-distance magnon propagation has been demonstrated via transport measurements, important thermodynamic properties of such magnon populations--including the magnon chemical potential and density--have thus far proven out of reach of experiments. Here, we present local measurements of the electron compressibility under the influence of magnons, which reveal a reduction of the gap by up to 20%. Combining these measurements with estimates of the temperature, our analysis reveals that the injected magnons bind to electrons and holes to form skyrmions, and it enables extraction of the free magnon density, magnon chemical potential, and average skyrmion spin. Our methods furnish a novel means of probing the thermodynamic properties of charge-neutral excitations that is applicable to other symmetry-broken electronic phases.
References in corpus (24)
- Quantum Hall Ferromagnetism in Graphene
- Spin and valley quantum Hall ferromagnetism in graphene
- Control and Local Measurement of the Spin Chemical Potential in a Magnetic Insulator
- Graphene integer quantum Hall effect in the ferromagnetic and paramagnetic regimes
- Collective Modes and Skyrmion Excitations in Graphene SU(4) Quantum Hall Ferromagnets
- Unconventional Sequence of Fractional Quantum Hall States in Suspended Graphene
- Twisted Bilayer Graphene V: Exact Analytic Many-Body Excitations in Twisted Bilayer Graphene Coulomb Hamiltonians: Charge Gap, Goldstone Modes and Absence of Cooper Pairing
- Fractional Quantum Hall Phase Transitions and Four-flux Composite Fermions in Graphene
- Long-Distance Spin Transport Through a Graphene Quantum Hall Antiferromagnet
- Hartree-Fock Theory of Skyrmions in Quantum Hall Ferromagnets
- Electrical generation and detection of spin waves in a quantum Hall ferromagnet
- Skyrmion solids in monolayer graphene
- Fractional and integer quantum Hall effects in the zeroth Landau level in graphene
- Spin Superfluidity in the Quantum Hall State of Graphene
- Spin excitation spectra of integral and fractional quantum Hall systems
- Magnons and skyrmions in fractional Hall ferromagnets
- Spin-valley skyrmions in graphene at filling factor
- SU(4) Skyrmions in the Quantum Hall State of Graphene
- Lattice Collective Modes from a Continuum Model of Magic-Angle Twisted Bilayer Graphene
- SU(4) spin waves in the quantum Hall ferromagnet in graphene
- Scattering of magnons at graphene quantum-Hall-magnet junctions
- Measurement of the electronic thermal conductance channels and heat capacity of graphene at low temperature
- Soft modes in magic angle twisted bilayer graphene
- Dissipative Transport in Quantum Hall Ferromagnets by Spinwave Scattering