On Sharp Enhancement of Effective Mass of Quasiparticles and Coefficient of T2 Term of Resistivity around First-Order Metamagnetic Transition Observed in UTe2

Abstract

The mechanism underlying the enhancement of the Sommerfeld coefficient of quasiparticles at the first-order metamagnetic transition in UTe_2, reported by Miyake et al. in J. Phys. Soc. Jpn. 88, 063706 (2019), is discussed theoretically by taking into account the ferromagnetic order-parameter fluctuations on the basis of the Landau theory of phase transition. We find that the enhanced ferromagnetic spin fluctuation gives rise to the enhancement of the effective mass of the quasiparticles or the Sommerfeld coefficient \gamma,which is consistent with the experimental observations. At the same time, the Kadowaki-Woods type scaling around the metamagnetic transition, reported by Imajo et al.in J. Phys. Soc. Jpn. 88, 083705 (2019) and Knafo et al. in J. Phys. Soc. Jpn. 88, 063705 (2019), is also understood semi-quantitatively by assuming reasonable values of parameters of Landau-type free energy reproducing key quantities characterizing the metamagnetic transition.