Effect of pressure on the pseudogap and charge density wave phases of the cuprate Nd-LSCO probed by thermopower measurements
Abstract
We report thermopower measurements under hydrostatic pressure on the cuprate superconductor La1.6 −xNd0.4SrxCuO4 (Nd-LSCO), at low temperature in the normal state accessed by suppressing superconductivity with a magnetic field up to H =31 T . Using an ac thermopower measurement technique suitable for high pressure and high field, we track the pressure evolution of the Seebeck coefficient S . At ambient pressure and low temperature, S /T in Nd-LSCO was recently found to suddenly increase below the pseudogap critical doping p★=0.23 , consistent with a drop in carrier density n from n =1 +p above p★ to n =p below. Under a pressure of 2.0 GPa, we observe that the large S /T value just below p★ is suppressed. This confirms a previous pressure study based on electrical resistivity and Hall effect, which found that pressure lowers p★, thereby reinforcing the interpretation that this effect is driven by the pressure-induced shift of the van Hove point. It implies that the pseudogap only exists when the Fermi surface is hole-like, which puts strong constraints on theories of the pseudogap phase. We also report thermopower measurements on Nd-LSCO and La1.8 −xEu0.2SrxCuO4 in the charge density wave phase near p ∼1 /8 , which reveals a weakening of this phase under pressure.
- Publication:
-
Physical Review Research
- Pub Date:
- April 2021
- DOI:
- 10.1103/PhysRevResearch.3.023066
- arXiv:
- arXiv:2012.10484
- Bibcode:
- 2021PhRvR...3b3066G
- Keywords:
-
- Condensed Matter - Superconductivity;
- Condensed Matter - Strongly Correlated Electrons
- E-Print:
- 9 pages, 5 figures