{"abstracts":[{"sha1":"636ebd861aefb54929874c0f90a97556f345623d","content":"Based on a special variant of plaquette expansion, an operator is constructed\nwhose eigenvalues give the low-energy singlet spectrum of spin-$\\frac12$\nHeisenberg antiferromagnet on square lattice with nearest- and frustrating\nnext-nearest-neighbor exchange couplings $J_1$ and $J_2$. It is well known that\na non-magnetic phase arises in this model at $0.4\\lesssim J_2/J_1\\lesssim 0.6$\nsandwiched by two N\\'eel ordered phases. In agreement with previous results, we\nobserve a first-order quantum phase transition (QPT) at $J_2\\approx 0.64J_1$\nfrom the non-magnetic phase to the N\\'eel one. Large gap ($\\gtrsim0.4J_1$) is\nfound in the singlet spectrum at $J_2<0.64J_1$ that excludes a gapless\nspin-liquid state at $0.4\\lesssim J_2/J_1\\lesssim 0.6$ and the deconfined\nquantum criticality scenario for the QPT to another N\\'eel phase. We observe a\nfirst-order QPT at $J_2\\approx 0.55J_1$ presumably between two non-magnetic\nphases.","mimetype":"text/plain","lang":"en"},{"sha1":"636ebd861aefb54929874c0f90a97556f345623d","content":"Based on a special variant of plaquette expansion, an operator is constructed\nwhose eigenvalues give the low-energy singlet spectrum of spin-$\\frac12$\nHeisenberg antiferromagnet on square lattice with nearest- and frustrating\nnext-nearest-neighbor exchange couplings $J_1$ and $J_2$. It is well known that\na non-magnetic phase arises in this model at $0.4\\lesssim J_2/J_1\\lesssim 0.6$\nsandwiched by two N\\'eel ordered phases. In agreement with previous results, we\nobserve a first-order quantum phase transition (QPT) at $J_2\\approx 0.64J_1$\nfrom the non-magnetic phase to the N\\'eel one. Large gap ($\\gtrsim0.4J_1$) is\nfound in the singlet spectrum at $J_2<0.64J_1$ that excludes a gapless\nspin-liquid state at $0.4\\lesssim J_2/J_1\\lesssim 0.6$ and the deconfined\nquantum criticality scenario for the QPT to another N\\'eel phase. We observe a\nfirst-order QPT at $J_2\\approx 0.55J_1$ presumably between two non-magnetic\nphases.","mimetype":"application/x-latex","lang":"en"}],"refs":[],"contribs":[{"index":0,"raw_name":"A. Yu. Aktersky","role":"author"},{"index":1,"raw_name":"A. V. Syromyatnikov","role":"author"}],"license_slug":"ARXIV-1.0","language":"en","version":"v1","ext_ids":{"arxiv":"1605.05152v1"},"release_year":2016,"release_date":"2016-05-17","release_stage":"submitted","release_type":"article","webcaptures":[],"filesets":[],"files":[{"release_ids":["7qw6gxj3inghrfz6up42w7opt4"],"mimetype":"application/pdf","urls":[{"url":"https://arxiv.org/pdf/1605.05152v1.pdf","rel":"repository"},{"url":"https://web.archive.org/web/20200915135128/https://arxiv.org/pdf/1605.05152v1.pdf","rel":"webarchive"}],"sha256":"bf45454f6be46e4f497c14df88175ceabeb5e7fa82ee68811652b1bd374675e8","sha1":"a32fc77e635ae1524489bea03850e714d0ded136","md5":"5d51bc8b9176cc610e592b33c2a7d013","size":1870305,"revision":"d3a273c6-2a0d-466c-86e4-16b66141b3b0","ident":"z7foy4t6bbcpbhh5c7uv45w2jy","state":"active"}],"work_id":"wgae2xuj2nc7nad4gvfft3ipiy","title":"Low-energy singlet sector in spin-1/2 J_1--J_2 Heisenberg\n model on square lattice","state":"active","ident":"7qw6gxj3inghrfz6up42w7opt4","revision":"4c1a9c0c-b816-475e-8492-d9472983a9d7","extra":{"arxiv":{"base_id":"1605.05152","categories":["cond-mat.str-el"],"journal_ref":"J. Exp. Theor. Phys. (2016) 123: 1035"}}}