Giant Seebeck effect across the field-induced metal-insulator transition of InAs

Alexandre Jaoui,Steffen Wiedmann,Carl Willem Rischau,Siham Benhabib,Gabriel Seyfarth,Kamran Behnia,Cyril Proust,Benoît Fauqué

doi:10.1038/s41535-020-00296-0

Abstract

Lightly doped III–V semiconductor InAs is a dilute metal, which can be pushed beyond its extreme quantum limit upon the application of a modest magnetic field. In this regime, a Mott-Anderson metal–insulator transition, triggered by the magnetic field, leads to a depletion of carrier concentration by more than one order of magnitude. Here, we show that this transition is accompanied by a 200-fold enhancement of the Seebeck coefficient, which becomes as large as 11.3 mV K−1approx 130frac{{k}_{B}}{e} at T = 8 K and B = 29 T. We find that the magnitude of this signal depends on sample dimensions and conclude that it is caused by phonon drag, resulting from a large difference between the scattering time of phonons (which are almost ballistic) and electrons (which are almost localized in the insulating state). Our results reveal a path to distinguish between possible sources of large thermoelectric response in other low-density systems pushed beyond the quantum limit.

Highlights

The thermoelectrical properties of low carrier density metals are of fundamental and technological interest
Our findings show that the field induces a metal–insulator transition (MIT) that is accompanied by a giant peak in the Seebeck effect, as large as Sxx = 11.3 mV K−1 at T = 8 K
The Fermi surface of InAs, studied by low magnetic field quantum oscillation measurements, is formed by a single spherical pocket located at the Γ-point of the Brillouin zone with a carrier density nSdH = 1.6 × 1016 cm−3 (TF = 100 K) and mass carrier m* = 0.023m0

Summary

INTRODUCTION

The thermoelectrical properties of low carrier density metals are of fundamental and technological interest. Can be large and, as such, used to develop high-performance thermoelectric devices[1] At low temperature, their thermoelectrical response is a fine probe of their fundamental electronic properties, in particular in the presence of a magnetic field[2]. A magnetic field of a few Tesla is enough to confine all the charge carriers in the lowest Landau level (LLL), the so-called quantum limit At low temperature, this is concomitant with an increase of Sxx (and Sxy)[7,8,9,10]. The natural thermoelectric scale of the diffusive response This surprisingly large Sxx can be either the result of an unbounded diffusive thermoelectric power specific to nodal metals[13] or to the coupling of electrons with the phonon bath. Our results demonstrate a new road to achieve large thermoelectric response that can be explored in other dilute metals recently identified

RESULTS

Jaoui et al 2

DISCUSSION

METHODS