Two-dimensional feature of the Nernst effect in normal state of underdoped La2 − xSrxCuO4 single crystals

The Nernst effect has been measured for an underdoped and an optimally doped La2 − xSrxCuO4 single crystal with the magnetic field applied along different directions. For both samples, when H∥c, a significant Nernst voltage appears above Tc and keeps measurable up to a high temperature (100 K). However, when H∥ab-plane the Nernst signal along the c-axis drops below the noise level quickly above Tc for the underdoped sample. Moreover, the in-plane Nernst data with field at different angles shows a nice scaling behavior with the c-axis component of the field. All these give a strong indication for a 2D feature of the Nernst signal in the normal state of underdoped cuprate superconductors.