We demonstrate a remarkable property of metallic Fermi liquids: the transverse conductivity
assumes a universal value in the quasi-static (ω → 0) limit for wavevectors q in the regime
l
−1
mfp q pF, where lmfp is the mean free path and pF is the Fermi momentum. This value is
(e2/h)RFS/q in two dimensions (2D), where RFS measures the local radius of curvature of the
Fermi surface (FS) in momentum space. Even more surprisingly, we find that U(1) spin liquids
with a spinon FS have the same universal transverse conductivity. This means such spin liquids
behave effectively as metals in this regime, even though they appear insulating in standard
transport experiments. Moreover, we show that transverse current fluctuations result in a universal
low-frequency magnetic noise that can be directly probed by a spin qubit, such as a
nitrogen-vacancy (NV) center in diamond, placed at a distance z above of the 2D metal or spin
liquid. Specifically the magnetic noise is given by CωPFS/z, where PFS is the perimeter of the FS in
momentum space and C is a combination of fundamental constants of nature. Therefore these
observables are controlled purely by the geometry of the FS and are independent of kinematic
details of the quasi-particles, such as their effective mass and interactions. This behavior can be
used as a new technique to measure the size of the FS of metals and as a smoking gun probe to
pinpoint the presence of the elusive spinon FS in two-dimensional systems. We estimate that this
universal regime is within reach of current NV center spectroscopic techniques for several spinon
FS candidate materials.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:85067 |
| Date | 02 May 2023 |
| Creators | Khoo, Jun Yong, Pientka, Falko, Sodemann, Inti |
| Publisher | IOP Publishing |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:article, info:eu-repo/semantics/article, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 1367-2630, 113009 |
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