title: Thermoelectric response near a quantum critical point of β-YbAlB4 and YbRh2Si2: a comparative study.
abstract: The thermoelectric coefficients have been measured down to a very low temperature for the Yb-based heavy-fermion compounds β-YbAlB4 and YbRh2Si2, often considered as model systems for the local quantum criticality case. We observe a striking difference in the behavior of the Seebeck coefficient S in the vicinity of their respective quantum critical point (QCP). Approaching the critical field, S/T is enhanced in β-YbAlB4, but drastically reduced in YbRh2Si2. The ratio of thermopower to specific heat remains constant for β-YbAlB4, but it is significantly reduced near the QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The interplay between valence and magnetic quantum criticality and the additional possibility of a Lifshitz transition crossing the critical field under magnetic field are discussed as the origin of the different behaviors of these compounds.
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Meguro, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Machida
authors.forename: K
authors.initials: K
authors.lastname: Tomokuni
authors.forename: C
authors.initials: C
authors.lastname: Ogura
authors.forename: K
authors.initials: K
authors.lastname: Izawa
authors.forename: K
authors.initials: K
authors.lastname: Kuga
authors.forename: S
authors.initials: S
authors.lastname: Nakatsuji
authors.forename: G
authors.initials: G
authors.lastname: Lapertot
authors.forename: G
authors.initials: G
authors.lastname: Knebel
authors.forename: J-P
authors.initials: JP
authors.lastname: Brison
authors.forename: J
authors.initials: J
authors.lastname: Flouquet