Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

In condensed matter physics, people always say quantum liquid or spin liquid. What does liquid mean?

share|improve this question

3 Answers 3

up vote 9 down vote accepted

Usually "quantum liquid" refers to the ground state of a Hamiltonian that do not break translation symmetry of the Hamiltonian. (In a sense, "quantum gas" = "quantum liquid".) "Quantum spin liquid" refers to the ground state of a spin Hamiltonian that do not break spin-rotation and translation symmetries of the Hamiltonian.

share|improve this answer

gas = particles are so little packed that they can easily move.

liquid = particles are fairly dense packed but can move over long distances.

solid = particles are so densely packed that they are confined to small vibrations araound an equilibrium position (site), and larger moves (site changes) are quite rare. In many cases, the sites form a periodic lattice; then we have a crystal.

Between these phases are so-called phase transitions, that provide (in the thermodynamic limit) a clear dividing line.

The prefix ''quantum'' just means that the motion of the particles cannot be described by classical mechanics.

share|improve this answer

Historically, the terms gas, liquid and (crystalline) solid meant, respectively: weak/no interactions between particles, strong interactions but statistical translation/orientation invariance, and finally breaking of translation/orientation invariance. Applied to more spin systems, a liquid would have translational invariance, but some global order --- i.e. not disordered like a "gas". Of course, this term is not absolutely precise, and often practitioners will define their terms in talks and papers. You should treat them as descriptive rather than normative.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.
{"cc_re__cc_re__cc_by_sa_3_0": ["        <li><a href=\"http://area51.stackexchange.com\" title=\"proposing new sites in the Stack Exchange network\">Area 51</a></li>\r\n                        <li><a href=\"http://careers.stackoverflow.com\">Stack Overflow Careers</a></li>\r\n                    \r\n                </ol>\r\n            </td>\r\n    </tr>\r\n</table>\r\n                </div>\r\n            </div>\r\n\r\n            <div id=\"copyright\">\r\n                site design / logo &#169; 2014 stack exchange inc; user contributions licensed under <a href=\"http://creativecommons.org/licenses/by-sa/3.0/\" rel=\"license\">cc by-sa 3.0</a> \r\n                with <a href=\"http://blog.stackoverflow.com/2009/06/attribution-required/\" rel=\"license\">attribution required</a>\r\n            </div>\r\n            <div id=\"svnrev\">\r\n                rev 2014.7.26.1729\r\n            </div>\r\n            \r\n        </div>\r\n    </div>\r\n    <noscript>\r\n        <div id=\"noscript-warning\">Physics Stack Exchange works best with JavaScript enabled<img src=\"http://pixel.quantserve.com/pixel/p-c1rF4kxgLUzNc.gif\" alt=\"\" class=\"dno\"></div>\r\n "], "copyright__copyright__copyright": ["quid would have translational invariance, but some global order --- i.e. not disordered like a \"gas\". Of course, this term is not absolutely precise, and often practitioners will define their terms in talks and papers. You should treat them as descriptive rather than normative.\n\nshare|improve this answer\n\nYour Answer\n\n\u00a0\ndiscard\n\nBy posting your answer, you agree to the privacy policy and terms of service.\n\nNot the answer you're looking for? Browse other questions tagged or ask your own question."]}