ELFT HÍRADÓ

[Janos Asboth <asboth AT phy.bme.hu>]

Meghívó

BME Elméleti Fizika Szeminárium,

szeptember 25. péntek 10h15,
online a Microsoft Teamsben,
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Dóra Balázs (BME TTK, Elméleti Fizika Tanszék):

Nuclear magnetic relaxation in Weyl semimetals

We investigate how the hyperfine coupling influences the NMR spin
relaxation time, T1, in Weyl semimetals. Since the density of states in
Weyl semimetals varies with the square of the energy around the Weyl point,
a naive power counting predicts that the nuclear spin relaxation rate 1/T1
would depend on the temperature (T) and the chemical pontential (mu) as
1/T1  ∼ T max(T, mu)^4. We carefully investigate the hyperfine interaction
between nuclear spins and Weyl fermions, and find that while its spin part
behaves conventionally, its orbital part diverges unusually with the
inverse of energy around the Weyl point. Consequently, in contrast with the
naive estimate, we find 1/T1 ∼ T max(T, mu)^2 ln(max(T,mu)/ω0), where ω0 is
the nuclear Larmor frequency. This allows us to identify an effective
hyperfine coupling constant, which is tunable by gating or doping. We also
analyze the recent experimental data on the nuclear spin-lattice relaxation
rate of the Weyl semimetal TaP. We argue that its non-monotonic temperature
dependence is explained by the temperature dependent chemical potential of
Weyl fermions.

Minden érdeklődőt szeretettel várunk.

Asbóth János
szemináriumi koordinátor