# Negative Absolute Temperature for Motional Degrees of Freedom

@article{Braun2013NegativeAT, title={Negative Absolute Temperature for Motional Degrees of Freedom}, author={Simon Braun and Jens Philipp Ronzheimer and Michael Schreiber and Sean S. Hodgman and Tim Rom and Immanuel Bloch and Ulrich Schneider}, journal={Science}, year={2013}, volume={339}, pages={52 - 55} }

Negative Is Hotter A common-sense perception of temperature tells us that the lower the temperature, the colder it is. However, below absolute zero, there is a netherworld of negative temperatures, which are, counterintuitively, hotter than positive temperatures. Usually, such states are achieved in the laboratory and are characterized by a higher occupation of high-energy versus low-energy states. This is most easily done for systems that have a finite spectrum of energy states, bounded from…

## 171 Citations

Negative Temperatures?

- PhysicsScience
- 2013

Ultracold quantum gases present an exquisitely tunable quantum system that can be tuned over seven orders of magnitude and from repulsive to attractive, and are used to produce a thermodynamic oddity—negative temperature.

Universe models with negative bulk viscosity

- Physics
- 2013

The concept of negative temperatures has occasionally been used in connection with quantum systems. A recent example of this sort is reported in the paper of S. Braun et al. (Science 339:52, 2013),…

Cosmology with negative absolute temperatures

- Physics
- 2016

Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions).…

A consistent description of fluctuations requires negative temperatures

- Physics
- 2015

We review two definitions of temperature in statistical mechanics, TB ?> and TG ?>, corresponding to two possible definitions of entropy, SB ?> and SG ?>, known as surface and volume entropy…

Consistent thermostatistics forbids negative absolute temperatures

- Physics
- 2014

Over the past 60 years, a considerable number of theories and experiments have claimed the existence of negative absolute temperature in spin systems and ultracold quantum gases. This has led to…

Negative specific heat with trapped ultracold quantum gases

- Physics
- 2014

The second law of thermodynamics normally prescribes that heat tends to disperse, but in certain cases it instead implies that heat will spontaneously concentrate. The spontaneous formation of stars…

Adiabatic demagnetization at absolute negative temperature: Generation of quantum correlations

- PhysicsInternational Journal of Quantum Information
- 2019

In this paper, we study behavior of the correlations, both quantum and classical, under adiabatic demagnetization process in systems of nuclear spins with dipole–dipole interactions in an external…

Statistical mechanics of systems with long-range interactions and negative absolute temperature.

- PhysicsPhysical review. E
- 2019

It is shown, by analytical computations, that there exists an energy interval in which the microcanonical entropy is a decreasing convex function of the total energy, meaning that ensemble equivalence is violated in a negative-temperature regime.

Finite Systems in a Heat Bath: Spectrum Perturbations and Thermodynamics.

- PhysicsThe journal of physical chemistry. B
- 2016

The theoretical framework proposed in this paper identifies the role of temperature in a bottom-up thermostatistical description of finite systems and shows that the temperature-induced spectrum perturbation is equivalent to Hill's purely thermodynamic subdivision potential.

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