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Title: Double-stage nematic bond ordering above double stripe magnetism: Application to BaTi 2 Sb 2 O

Spin-driven nematicity, or the breaking of the point-group symmetry of the lattice without long-range magnetic order, is clearly quite important in iron-based superconductors. From a symmetry point of view, nematic order can be described as a coherent locking of spin fluctuations in two interpenetrating Néel sublattices with ensuing nearest-neighbor bond order and an absence of static magnetism. In this paper, we argue that the low-temperature state of the recently discovered superconductor BaTi 2 Sb 2 O is a strong candidate for a more exotic form of spin-driven nematic order, in which fluctuations occurring in four Néel sublattices promote both nearest- and next-nearest-neighbor bond order. We develop a low-energy field theory of this state and show that it can have, as a function of temperature, up to two separate bond-order phase transitions, namely, one that breaks rotation symmetry and one that breaks reflection and translation symmetries of the lattice. The resulting state has an orthorhombic lattice distortion, an intra-unit-cell charge density wave, and no long-range magnetic order, all consistent with reported measurements of the low-temperature phase of BaTi 2 Sb 2 O . Finally, we then use density functional theory calculations to extract exchange parameters to confirm that the model is applicable to BaTi 2 Sb 2 O .
Authors:
 [1] ;  [2] ;  [1] ;  [2] ;  [3]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy. Division of Materials Science and Engineering
  2. Naval Research Lab. (NRL), Washington, DC (United States)
  3. Univ. of Minnesota, Minneapolis, MN (United States). School of Physics and Astronomy
Publication Date:
Grant/Contract Number:
SC0012336; AC02-07CH11358; PHYS-1066293
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 17; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Univ. of Minnesota, Minneapolis, MN (United States); Ames Lab. and Iowa State Univ., Ames, IA (United States); Naval Research Lab. (NRL), Washington, DC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Office of Naval Research (ONR) (United States); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1362273
Alternate Identifier(s):
OSTI ID: 1354753