The Nernst effect in Corbino geometry

Kavokin, Alexey; Altshuler, B. L.; Sharapov, S. G.; Grigoryev, P. S.; Varlamov, A. A.

doi:10.1073/pnas.1916567117

“…Another established transport geometry is a two-terminal Corbino ring. The ring shape allows for circulating current components, and provides access to additional bulk transport properties 26 , 27 . In the context of topological materials with edge channels, the obvious limitation for such traditional Corbino setting is the absence of material edges extending directly between both contacts, making such measurement sensitive solely to the conductance in the bulk, and insensitive to the existence of edge channels.…”

Section: Introductionmentioning

confidence: 99%

Quantum anomalous Hall edge channels survive up to the Curie temperature

Fijalkowski

¹

,

Liu

²

,

Mandal

³

et al. 2021

View full text Add to dashboard Cite

Achieving metrological precision of quantum anomalous Hall resistance quantization at zero magnetic field so far remains limited to temperatures of the order of 20 mK, while the Curie temperature in the involved material is as high as 20 K. The reason for this discrepancy remains one of the biggest open questions surrounding the effect, and is the focus of this article. Here we show, through a careful analysis of the non-local voltages on a multi-terminal Corbino geometry, that the chiral edge channels continue to exist without applied magnetic field up to the Curie temperature of bulk ferromagnetism of the magnetic topological insulator, and that thermally activated bulk conductance is responsible for this quantization breakdown. Our results offer important insights on the nature of the topological protection of these edge channels, provide an encouraging sign for potential applications, and establish the multi-terminal Corbino geometry as a powerful tool for the study of edge channel transport in topological materials.

show abstract

“…The phenomenon is well-understood [37], but the experiments are only a few. In the Corbino geometry, the azimuthal Nernst thermocurrent is predicted to be oscillatory [38]. Graphene is especially important for these studies because the quantum Hall effect persists to relative high temperatures, which is essential to make good measurements of the quantized thermopower [39,40].…”

Section: Quantum-thermal Effects In 2deg and Graphenementioning

confidence: 99%

A Coherent and Unified Single Particle Description of the Integer and Fractional Quantum Hall Effects

Unnikrishnan

2021

Preprint

0

View full text Add to dashboard Cite

There are compelling reasons to seek a new coherent description of the Quantum Hall Effects (QHE). The theoretical descriptions of the 'Integer' (IQHE) and the 'Fractional' (FQHE) quantum Hall effects are very different at present, despite their remarkable phenomenological similarity. In particular, the fractional effect invokes multi-particle dynamics and collective phenomena in the presence of a dominant Coulomb interaction, in a complex hierarchical scheme, whereas the integer effect is mostly a simple weakly interacting single particle scenario. The experimental situation, in contrast, shows that both the effects appear seamlessly, intermingling progressively, as either the magnetic field or the carrier density is monotonically varied. I argue and prove that a crucial physics input that is missing in the current theories is the relativistic gravitational contribution of all the matter-energy in the Universe. The dynamically induced relativistic gravitational potentials play a startling role to modify the quantum degeneracy, by coupling to the mass of electrons in the noninertial cyclotron orbitals. The key point is that the quantum degeneracy of Landau levels, due to the applied magnetic field, is modified by the relativistically induced cosmic gravitomagnetic field, thereby making the degeneracy dependent on the number density of the electrons. I successfully derive the main characteristics and the full sequence of both IQHE and FHQE in a seamless unified single particle scenario, without any quasiparticles, particle-flux composites, or extraneous postulates. Apart from correctly reproducing all the observed filling factors in the IQHE and the FQHE for the filling factors ν ≥ 1/3, this new theory of the QHE based on the cosmic gravitational effects has the natural explanation for the absence of the QHE at even fractions for ν < 1. Further, there is a consistent description of the edge state physics, for both charge transport and thermal transport, in the FQHE states. The gravitational paradigm shows clearly the physical reason for the phenomenological success of the effective theories with the quasiparticles like the Composite Fermions.

show abstract

“…Another established transport geometry is a twoterminal Corbino ring. The ring shape allows for circulating current components, and provides access to additional bulk transport properties [26,27]. In the context of topological materials with edge channels, the obvious limitation for such traditional Corbino setting is the absence of material edges extending directly between both contacts, making such measurement sensitive solely to the conductance in the bulk, and insensitive to the existence of edge channels.…”

Section: Introductionmentioning

confidence: 99%

Quantum anomalous Hall edge channels survive up to the Curie temperature

Fijalkowski,

Liu,

Mandal

et al. 2021

Preprint

0

View full text Add to dashboard Cite

Achieving metrological precision of quantum anomalous Hall resistance quantization at zero magnetic field so far remains limited to temperatures of the order of 20 mK, while the Curie temperature in the involved material is as high as 20 K. The reason for this discrepancy remains one of the biggest open questions surrounding the effect, and is the focus of this article. Here we show, through a careful analysis of the non-local voltages on a multi-terminal Corbino geometry, that the chiral edge channels continue to exist without applied magnetic field up to the Curie temperature of bulk ferromagnetism of the magnetic topological insulator, and that thermally activated bulk conductance is responsible for this quantization breakdown. Our results offer important insights on the nature of the topological protection of these edge channels, provide an encouraging sign for potential applications, and establish the multi-terminal Corbino geometry as a powerful tool for the study of edge channel transport in topological materials.

show abstract

The Nernst effect in Corbino geometry

Cited by 16 publications

References 44 publications

Quantum anomalous Hall edge channels survive up to the Curie temperature

Quantum anomalous Hall edge channels survive up to the Curie temperature

A Coherent and Unified Single Particle Description of the Integer and Fractional Quantum Hall Effects

Quantum anomalous Hall edge channels survive up to the Curie temperature

Contact Info

Product

Resources

About