Diagonal Nematicity in the Pseudogap Phase of HgBa$_2$CuO$_{4+δ}$

H. Murayama; Y. Sato; R. Kurihara; S. Kasahara; Y. Mizukami; Y. Kasahara; H. Uchiyama; A. Yamamoto; E. -G. Moon; J. Cai; J. Freyermuth; M. Greven; T. Shibauchi; Y. Matsuda

doi:10.1038/s41467-019-11200-1

paper

Diagonal Nematicity in the Pseudogap Phase of HgBa $_{2}$ CuO $_{4 + δ}$

arXiv:1805.00276 · doi:10.1038/s41467-019-11200-1

Abstract

The pseudogap phenomenon in cuprates is the most mysterious puzzle in the research of high-temperature superconductivity. In particular, whether the pseudogap is associated with a crossover or phase transition has been a long-standing controversial issue. The tetragonal cuprate HgBa $_{2}$ CuO $_{4 + δ}$ , with only one CuO $_{2}$ layer per primitive cell, is an ideal system to tackle this puzzle. Here, we measure the anisotropy of magnetic susceptibility within the CuO $_{2}$ plane with exceptionally high-precision magnetic torque experiments. Our key finding is that a distinct two-fold in-plane anisotropy sets in below the pseudogap temperature $T^{*}$ , which provides thermodynamic evidence for a nematic phase transition with broken four-fold symmetry. Most surprisingly, the nematic director orients along the diagonal direction of the CuO $_{2}$ square lattice, in sharp contrast to the bond nematicity reported in various iron-based superconductors and double-layer YBa $_{2}$ Cu $_{3}$ O $_{6 + δ}$ , where the anisotropy axis is along the Fe-Fe and Cu-O-Cu directions, respectively. Another remarkable feature is that the enhancement of the diagonal nematicity with decreasing temperature is suppressed around the temperature at which short-range charge-density-wave (CDW) formation occurs. This is in stark contrast to YBa $_{2}$ Cu $_{3}$ O $_{6 + δ}$ , where the bond nematicity is not influenced by the CDW. Our result suggests a competing relationship between diagonal nematic and CDW order in HgBa $_{2}$ CuO $_{4 + δ}$ .

7 pages, 8 figures

Diagonal Nematicity in the Pseudogap Phase of HgBa2​CuO4+δ​

Abstract

Diagonal Nematicity in the Pseudogap Phase of HgBa $_{2}$ CuO $_{4 + δ}$