Thermopower across the phase diagram of the cuprate La1.6−xNd0.4SrxCuO4 : signatures of the pseudogap and charge-density-wave phases
Département de physique
Université de Sherbrooke
Research professional in Taillefer's group
Présentation en anglais
Lien Zoom: https://umontreal.zoom.us/j/93026432919
Meeting ID: 930 2643 2919
Passcode: écrire en chiffre: un, trois, sept.
Abstract: The Seebeck coefficient (thermopower) S of the cuprate superconductor La1.6−xNd0.4SrxCuO4 was measured across its doping phase diagram (from p= 0.12 to p= 0.25), at various temperatures down to T ≈ 2 K, in the normal state accessed by suppressing superconductivity with a magnetic field up to H= 37.5 T. The magnitude of S/T in the T= 0 limit is found to suddenly increase, by a factor ≈ 5, when the doping is reduced below p* = 0.23, the critical doping for the onset of the pseudogap phase. This confirms that the pseudogap phase causes a large reduction of the carrier density n, consistent with a drop from n= 1 +p above p* to n=p below p*, as previously inferred from measurements of the Hall coefficient, resistivity and thermal conductivity. When the doping is reduced below p= 0.19, a qualitative change is observed whereby S/T decreases as T→0,eventually to reach negative values at T= 0. In prior work on other cuprates, negative values of S/T at T→0 were shown to result from a reconstruction of the Fermi surface caused by charge-density-wave (CDW) order. We therefore identify pCDW ≈ 0.19 as the critical doping beyond which there is no CDW-induced Fermi surface reconstruction. The fact that pCDW is well separated from p* reveals that there is a doping range below p* where the transport signatures of the pseudogap phase are unaffected by CDW correlations, as previously found in YBa2Cu3Oy and La2−xSrxCuO4.
Cette conférence est présentée par le RQMP.