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San Jose State University

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Full-Text Articles in Physics

Attending To Scientific Practices Within Undergraduate Research Experiences, Gina Quan, Chandra Turpen, Andrew Elby Jul 2016

Attending To Scientific Practices Within Undergraduate Research Experiences, Gina Quan, Chandra Turpen, Andrew Elby

Faculty Publications

Ford (2015) argues for viewing "scientific practice" not as a list of particular skills, but rather, as "sets of regularities of behaviors and social interactions" among scientists. This conceptualization of scientific practices foregrounds how they 1) meaningfully connect to one another, 2) are purposefully employed in their ability to explain nature and 3) prospectively adapt based on critique. While Ford focused on practices in K-12 classrooms, we apply this framework to understand how undergraduate physics majors do or do not make progress toward more central participation in physics research experiences. Using video from interviews with students and research mentors, and …

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Energy Tracking Diagrams, Rachel Scherr, Benedikt Harrer, Hunter Close, Abigail Daane, Lezlie Dewater, Amy Robertson, Lane Seeley, Stamatis Vokos Jan 2016

Energy Tracking Diagrams, Rachel Scherr, Benedikt Harrer, Hunter Close, Abigail Daane, Lezlie Dewater, Amy Robertson, Lane Seeley, Stamatis Vokos

Faculty Publications

Energy is a crosscutting concept in science and features prominently in national science education documents. In the Next Generation Science Standards, the primary conceptual learning goal is for learners to conserve energy as they track the transfers and transformations of energy within, into, or out of the system of interest in complex physical processes. As part of tracking energy transfers among objects, learners should (i) distinguish energy from matter, including recognizing that energy flow does not uniformly align with the movement of matter, and should (ii) identify specific mechanisms by which energy is transferred among objects, such as mechanical work …

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Cooling Atomic Gases With Disorder, Ehsan Khatami, Thereza Paiva, Shuxiang Yang, Valéry Rousseau, Mark Jarrell, Juana Moreno, Randall Hulet, Richard Scalettar Dec 2015

Cooling Atomic Gases With Disorder, Ehsan Khatami, Thereza Paiva, Shuxiang Yang, Valéry Rousseau, Mark Jarrell, Juana Moreno, Randall Hulet, Richard Scalettar

Faculty Publications

Cold atomic gases have proven capable of emulating a number of fundamental condensed matter phenomena including Bose-Einstein condensation, the Mott transition, Fulde-Ferrell-Larkin-Ovchinnikov pairing, and the quantum Hall effect. Cooling to a low enough temperature to explore magnetism and exotic superconductivity in lattices of fermionic atoms remains a challenge. We propose a method to produce a low temperature gas by preparing it in a disordered potential and following a constant entropy trajectory to deliver the gas into a nondisordered state which exhibits these incompletely understood phases. We show, using quantum Monte Carlo simulations, that we can approach the Néel temperature of …

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Observation Of Antiferromagnetic Correlations In The Hubbard Model With Ultracold Atoms, Russell Hart, Pedro Duarte, Tsung-Lin Yang, Xinxing Liu, Thereza Paiva, Ehsan Khatami, Richard Scalettar, Nandini Trivedi, David Huse, Randall Hulet Mar 2015

Observation Of Antiferromagnetic Correlations In The Hubbard Model With Ultracold Atoms, Russell Hart, Pedro Duarte, Tsung-Lin Yang, Xinxing Liu, Thereza Paiva, Ehsan Khatami, Richard Scalettar, Nandini Trivedi, David Huse, Randall Hulet

Faculty Publications

Ultracold atoms in optical lattices have great potential to contribute to a better understanding of some of the most important issues in many-body physics, such as high-temperature superconductivity. The Hubbard model—a simplified representation of fermions moving on a periodic lattice—is thought to describe the essential details of copper oxide superconductivity. This model describes many of the features shared by the copper oxides, including an interaction-driven Mott insulating state and an antiferromagnetic (AFM) state. Optical lattices filled with a two-spin-component Fermi gas of ultracold atoms can faithfully realize the Hubbard model with readily tunable parameters, and thus provide a platform for …

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Compressibility Of A Fermionic Mott Insulator Of Ultracold Atoms, Pedro Duarte, Russell Hart, Tsung-Lin Yang, Xinxing Liu, Thereza Paiva, Ehsan Khatami, Richard Scalettar, Nandini Trivedi, Randall Hulet Feb 2015

Compressibility Of A Fermionic Mott Insulator Of Ultracold Atoms, Pedro Duarte, Russell Hart, Tsung-Lin Yang, Xinxing Liu, Thereza Paiva, Ehsan Khatami, Richard Scalettar, Nandini Trivedi, Randall Hulet

Faculty Publications

We characterize the Mott insulating regime of a repulsively interacting Fermi gas of ultracold atoms in a three-dimensional optical lattice. We use in situ imaging to extract the central density of the gas and to determine its local compressibility. For intermediate to strong interactions, we observe the emergence of a plateau in the density as a function of atom number, and a reduction of the compressibility at a density of one atom per site, indicating the formation of a Mott insulator. Comparisons to state-of-the-art numerical simulations of the Hubbard model over a wide range of interactions reveal that the temperature …

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Finite-Temperature Superconducting Correlations Of The Hubbard Model, Ehsan Khatami, Richard Scalettar, Rajiv Singh Jan 2015

Finite-Temperature Superconducting Correlations Of The Hubbard Model, Ehsan Khatami, Richard Scalettar, Rajiv Singh

Faculty Publications

We utilize numerical linked-cluster expansions (NLCEs) and the determinantal quantum Monte Carlo algorithm to study pairing correlations in the square-lattice Hubbard model. To benchmark the NLCE, we first locate the finite-temperature phase transition of the attractive model to a superconducting state away from half filling. We then explore the superconducting properties of the repulsive model for the d-wave and extended s-wave pairing symmetries. The pairing structure factor shows a strong tendency to d-wave pairing and peaks at an interaction strength comparable to the bandwidth. The extended s-wave structure factor and correlation length are larger at higher temperatures but clearly saturate …

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Geometry Dependence Of The Sign Problem In Quantum Monte Carlo Simulations, V. Iglovikov, Ehsan Khatami, R. Scalettar Jan 2015

Geometry Dependence Of The Sign Problem In Quantum Monte Carlo Simulations, V. Iglovikov, Ehsan Khatami, R. Scalettar

Faculty Publications

The sign problem is the fundamental limitation to quantum Monte Carlo simulations of the statistical mechanics of interacting fermions. Determinant quantum Monte Carlo (DQMC) is one of the leading methods to study lattice fermions, such as the Hubbard Hamiltonian, which describe strongly correlated phenomena including magnetism, metal-insulator transitions, and possibly exotic superconductivity. Here, we provide a comprehensive dataset on the geometry dependence of the DQMC sign problem for different densities, interaction strengths, temperatures, and spatial lattice sizes. We supplement these data with several observations concerning general trends in the data, including the dependence on spatial volume and how this can …

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Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar Sep 2014

Magnetic Correlations And Pairing In The 1/5-Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar

Faculty Publications

We study the single-orbital Hubbard model on the 1/5-depleted square-lattice geometry, which arises in such diverse systems as the spin-gap magnetic insulator CaV4O9 and ordered-vacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a block-spin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel phase. …

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Perturbative Unitarity Constraints On A Supersymmetric Higgs Portal, Kassahun Betre, Sonia Hedri, Devin Walker Jul 2014

Perturbative Unitarity Constraints On A Supersymmetric Higgs Portal, Kassahun Betre, Sonia Hedri, Devin Walker

Faculty Publications

We place perturbative unitarity constraints on both the dimensionful and dimensionless couplings in the Next-to-Minimal Supersymmetric Standard Model Higgs Sector. These constraints, plus the requirement that the singlino and/or Higgsino constitutes at least part of the observed dark matter relic abundance, generate upper bounds on the Higgs and neutralino/chargino mass spectrum. We obtain an upper bound of 12 TeV for the charginos and neutralinos and 20 TeV for the heavy Higgses outside defined fine-tuned regions. By using the NMSSM as a template, we describe a method which replaces naturalness arguments with more rigorous perturbative unitarity arguments to get a better …

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Investigating Access To And Attitudes Toward Programming In A Physics Camp, Gina Quan, Ayush Gupta Jul 2014

Investigating Access To And Attitudes Toward Programming In A Physics Camp, Gina Quan, Ayush Gupta

Faculty Publications

Computer programming has become a critical skill in much of physics research and undergraduate physics coursework. Our aim is to understand students' complex relationships (epistemological and affective associations) to coding and design, and in particular, how they experience and perceive access to programming in physics contexts. We piloted a project-based instructional module using Arduino Rovers (Arduino-integrated programmable robot-tanks) in a summer camp for high school students hosted by University of Maryland Physics Department. Throughout the program, participants worked through several open-ended design tasks before designing and completing a final project. In interviews, we asked students to reflect on their experiences …

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Linked-Cluster Expansion For The Green's Function Of The Infinite-U Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry Jun 2014

Linked-Cluster Expansion For The Green's Function Of The Infinite-U Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry

Faculty Publications

We implement a highly efficient strong-coupling expansion for the Green's function of the Hubbard model. In the limit of extreme correlations, where the onsite interaction is infinite, the evaluation of diagrams simplifies dramatically enabling us to carry out the expansion to the eighth order in powers of the hopping amplitude. We compute the finite-temperature Green's function analytically in the momentum and Matsubara frequency space as a function of the electron density. Employing Padé approximations, we study the equation of state, Kelvin thermopower, momentum distribution function, quasiparticle fraction, and quasiparticle lifetime of the system at temperatures lower than, or of the …

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The Real-Time Instructor Observing Tool For Future Teachers, Cassandra Paul May 2014

The Real-Time Instructor Observing Tool For Future Teachers, Cassandra Paul

Faculty Publications

Current educational research shows that students achieve higher learning gains in science classrooms when interactive techniques are used. As a result, we are seeing more high schools and institutions of higher education adopt interactive courses. Unfortunately, it's difficult for future teachers to envision interactive science courses because their experience as students has been dominated by traditional lecture. New educators need to know what interactive science classrooms look like, so that they can model this experience in their own classrooms. The Real-time Instructor Observing Tool (RIOT), a computer application that allows an observer to quickly categorize classroom interactions, can help with …

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Three-Point Current Correlation Functions As Probes Of Effective Conformal Theories, Kassahun Betre Apr 2014

Three-Point Current Correlation Functions As Probes Of Effective Conformal Theories, Kassahun Betre

Faculty Publications

See abstract in PDF.

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Grading By Response Category: A Simple Method For Providing Students With Meaningful Feedback On Exams In Large Courses, Cassandra Paul, Wendell Potter, Brenda Weiss Jan 2014

Grading By Response Category: A Simple Method For Providing Students With Meaningful Feedback On Exams In Large Courses, Cassandra Paul, Wendell Potter, Brenda Weiss

Faculty Publications

As instructors, we want our students to develop a deep understanding of course material, and feedback is essential in their sense-making process. Providing effective individualized feedback to students in large courses is especially difficult. While researcherssuggest,1 and many instructors of large courses are,2,3incorporating interactive techniques that allow peer feedback, studies have shown that it's important for students to also have direct feedback from the instructor.4 Since the requirement for individualized feedback is difficult to meet during class time in large courses, providing effective feedback on exams and quizzes takes on added importance. Some instructors choose to …

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Sixteen Years Of Collaborative Learning Through Active Sense-Making In Physics (Clasp) At Uc Davis, Wendell Potter, David Webb, Cassandra Paul, Emily West, Mark Bowen, Brenda Weiss, Lawrence Coleman, Charles De Leone Jan 2014

Sixteen Years Of Collaborative Learning Through Active Sense-Making In Physics (Clasp) At Uc Davis, Wendell Potter, David Webb, Cassandra Paul, Emily West, Mark Bowen, Brenda Weiss, Lawrence Coleman, Charles De Leone

Faculty Publications

This paper describes our large reformed introductory physics course at UC Davis, which bioscience students have been taking since 1996. The central feature of this course is a focus on sense-making by the students during the five hours per week discussion/labs in which the students take part in activities emphasizing peer-peer discussions, argumentation, and presentations of ideas. The course differs in many fundamental ways from traditionally taught introductory physics courses. After discussing the unique features of CLASP and its implementation at UC Davis, various student outcome measures are presented showing increased performance by students who took the CLASP course compared …

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Low Mach Number Fluctuating Hydrodynamics Of Diffusively Mixing Fluids, Aleksandar Donev, Andy J. Nonaka, Yifei Sun, Thomas Fai, Alejandro Garcia, John B. Bell Jan 2014

Low Mach Number Fluctuating Hydrodynamics Of Diffusively Mixing Fluids, Aleksandar Donev, Andy J. Nonaka, Yifei Sun, Thomas Fai, Alejandro Garcia, John B. Bell

Faculty Publications

We formulate low Mach number fluctuating hydrodynamic equations appropriate for modeling diffusive mixing in isothermal mixtures of fluids with different density and transport coefficients. These equations eliminate the fast isentropic fluctuations in pressure associated with the propagation of sound waves by replacing the equation of state with a local thermodynamic constraint. We demonstrate that the low Mach number model preserves the spatio-temporal spectrum of the slower diffusive fluctuations. We develop a strictly conservative finite-volume spatial discretization of the low Mach number fluctuating equations in both two and three dimensions. We construct several explicit Runge-Kutta temporal integrators that strictly maintain the …

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Fluctuation-Dissipation Theorem In Isolated Quantum Systems Out Of Equilibrium, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol Jan 2014

Fluctuation-Dissipation Theorem In Isolated Quantum Systems Out Of Equilibrium, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol

Faculty Publications

We study the validity of the fluctuation-dissipation theorem for an isolated quantum system of harmonically trapped dipolar molecules taken out of equilibrium by means of a quench, a sudden change in the Hamiltonian parameters. We find that the integrability of the system plays a crucial role in the validity of the fluctuation-dissipation theorem. Namely, the system thermalizes according to the eigenstate thermalization hypothesis and the theorem holds if the system is nonintegrable after the quench. However, it fails if the system is integrable, unless the initial state is an eigenstate of a nonintegrable Hamiltonian, in which case the system still …

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Finite-Temperature Properties Of Strongly Correlated Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marchos Rigol Sep 2013

Finite-Temperature Properties Of Strongly Correlated Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marchos Rigol

Faculty Publications

We study finite-temperature properties of strongly interacting fermions in the honeycomb lattice using numerical linked-cluster expansions and determinantal quantum Monte Carlo simulations. We analyze a number of thermodynamic quantities, including the entropy, the specific heat, uniform and staggered spin susceptibilities, short-range spin correlations, and the double occupancy at and away from half filling. We examine the viability of adiabatic cooling by increasing the interaction strength for homogeneous as well as for trapped systems. For the homogeneous case, this process is found to be more efficient at finite doping than at half filling. That, in turn, leads to an efficient adiabatic …

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Fluctuation-Dissipation Theorem In An Isolated System Of Quantum Dipolar Bosons After A Quench, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol Jul 2013

Fluctuation-Dissipation Theorem In An Isolated System Of Quantum Dipolar Bosons After A Quench, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol

Faculty Publications

We examine the validity of fluctuation-dissipation relations in isolated quantum systems taken out of equilibrium by a sudden quench. We focus on the dynamics of trapped hard-core bosons in one-dimensional lattices with dipolar interactions whose strength is changed during the quench. We find indications that fluctuation-dissipation relations hold if the system is nonintegrable after the quench, as well as if it is integrable after the quench if the initial state is an equilibrium state of a nonintegrable Hamiltonian. On the other hand, we find indications that they fail if the system is integrable both before and after quenching.

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Electronic Spectral Properties Of The Two-Dimensional Infinite-U Hubbard Model, Ehsan Khatami, Daniel Hansen, Edward Perepelitsky, Marcos Rigol, Sriram Shastry Apr 2013

Electronic Spectral Properties Of The Two-Dimensional Infinite-U Hubbard Model, Ehsan Khatami, Daniel Hansen, Edward Perepelitsky, Marcos Rigol, Sriram Shastry

Faculty Publications

A strong-coupling series expansion for the Green's function and the extremely correlated Fermi liquid (ECFL) theory are used to calculate the moments of the electronic spectral functions of the infinite-U Hubbard model. Results from these two complementary methods agree very well at both low densities, where the ECFL solution is the most accurate, and at high to intermediate temperatures, where the series converge. We find that a modified first moment, which underestimates the contributions from the occupied states and is accessible in the series through the time-dependent Green's function, best describes the peak location of the spectral function in the …

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Variation Of Instructor-Student Interactions In An Introductory Interactive Physics Course, Emily West, Cassandra Paul, David Webb, Wendell Potter Mar 2013

Variation Of Instructor-Student Interactions In An Introductory Interactive Physics Course, Emily West, Cassandra Paul, David Webb, Wendell Potter

Faculty Publications

The physics instruction at UC Davis for life science majors takes place in a long-standing reformed large-enrollment physics course in which the discussion or laboratory instructors (primarily graduate student teaching assistants) implement the interactive-engagement (IE) elements of the course. Because so many different instructors participate in disseminating the IE course elements, we find it essential to the instructors’ professional development to observe and document the student-instructor interactions within the classroom. Out of this effort, we have developed a computerized real-time instructor observation tool (RIOT) to take data of student-instructor interactions. We use the RIOT to observe 29 different instructors for …

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A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol Mar 2013

A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol

Faculty Publications

We provide a pedagogical introduction to numerical linked-cluster expansions (NLCEs). We sketch the algorithm for generic Hamiltonians that only connect nearest-neighbor sites in a finite cluster with open boundary conditions. We then compare results for a specific model, the Heisenberg model, in each order of the NLCE with the ones for the finite cluster calculated directly by means of full exact diagonalization. We discuss how to reduce the computational cost of the NLCE calculations by taking into account symmetries and topologies of the linked clusters. Finally, we generalize the algorithm to the thermodynamic limit, and discuss several numerical resummation techniques …

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Students Talk About Energy In Project- Based Inquiry Science, Benedikt W. Harrer, Virginia J. Flood, Michael C. Wittmann Jan 2013

Students Talk About Energy In Project- Based Inquiry Science, Benedikt W. Harrer, Virginia J. Flood, Michael C. Wittmann

Faculty Publications

We examine the types of emergent language eighth grade students in rural Maine middle schools use when they discuss energy in their first experiences with Project-Based Inquiry Science: Energy, a research-based curriculum that uses a specific language for talking about energy. By comparative analysis of the language used by the curriculum materials to students’ language, we find that students’ talk is at times more aligned with a Stores and Transfer model of energy than the Forms model supported by the curriculum.

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Productive Resources In Students’ Ideas About Energy: An Alternative Analysis Of Watts’ Original Interview Transcripts, Benedikt W. Harrer, Virginia J. Flood, Michael C. Wittmann Jan 2013

Productive Resources In Students’ Ideas About Energy: An Alternative Analysis Of Watts’ Original Interview Transcripts, Benedikt W. Harrer, Virginia J. Flood, Michael C. Wittmann

Faculty Publications

For over 30 years, researchers have investigated students’ ideas about energy with the intent of reforming instructional practice. In this pursuit, Watts contributed an influential study with his 1983 paper “Some alternative views of energy” [Phys. Educ. 18, 213 (1983)]. Watts’ “alternative frameworks” continue to be used for categorizing students’ non-normative ideas about energy. Using a resources framework, we propose an alternate analysis of student responses from Watts’ interviews. In our analysis, we show how students’ activated resources about energy are disciplinarily productive. We suggest that fostering seeds of scientific understandings in students’ ideas about energy may play an important …

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Effect Of Particle Statistics In Strongly Correlated Two-Dimensional Hubbard Models, Ehsan Khatami, Marcos Rigol Aug 2012

Effect Of Particle Statistics In Strongly Correlated Two-Dimensional Hubbard Models, Ehsan Khatami, Marcos Rigol

Faculty Publications

We study the onset of particle statistics effects as the temperature is lowered in strongly correlated two-dimensional Hubbard models. We utilize numerical linked-cluster expansions and focus on the properties of interacting lattice fermions and two-component hard-core bosons. In the weak-coupling regime, where the ground state of the bosonic system is a superfluid, the thermodynamic properties of the two systems at half filling exhibit very large differences even at high temperatures. In the strong-coupling regime, where the low-temperature behavior is governed by a Mott insulator for either particle statistics, the agreement between the thermodynamic properties of both systems extends to regions …

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Student-Teacher Interactions For Bringing Out Student Ideas About Energy, Benedikt W. Harrer, Michael Wittmann, Rachel Scherr Aug 2012

Student-Teacher Interactions For Bringing Out Student Ideas About Energy, Benedikt W. Harrer, Michael Wittmann, Rachel Scherr

Faculty Publications

Modern middle school science curricula use group activities to help students express their thinking and enable them to work together like scientists. We are studying rural 8th grade science classrooms using materials on energy. Even after spending several months with the same curriculum on other physics topics, students' engagement in group activities seems to be restricted to creating lists of words that are associated with energy. Though research suggests that children have rich and potentially valuable ideas about energy, our students don't seem to spontaneously use and express their ideas in the classroom. Only within or after certain interactions with …

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Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio García-García May 2012

Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio García-García

Faculty Publications

We study spectral properties and the dynamics after a quench of one-dimensional spinless fermions with short-range interactions and long-range random hopping. We show that a sufficiently fast decay of the hopping term promotes localization effects at finite temperature, which prevents thermalization even if the classical motion is chaotic. For slower decays, we find that thermalization does occur. However, within this model, the latter regime falls in an unexpected universality class, namely, observables exhibit a power-law (as opposed to an exponential) approach to their thermal expectation values.

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Numerical Study Of The Thermodynamics Of Clinoatacamite, Ehsan Khatami, Joel Helton, Marcos Rigol Feb 2012

Numerical Study Of The Thermodynamics Of Clinoatacamite, Ehsan Khatami, Joel Helton, Marcos Rigol

Faculty Publications

We study the thermodynamic properties of the clinoatacamite compound, Cu2(OH)3Cl, by considering several approximate models. They include the Heisenberg model on (i) the uniform pyrochlore lattice, (ii) a very anisotropic pyrochlore lattice, and (iii) a kagome lattice weakly coupled to spins that sit on a triangular lattice. We utilize the exact diagonalization of small clusters with periodic boundary conditions and implement a numerical linked-cluster expansion approach for quantum lattice models with reduced symmetries, which allows us to solve model (iii) in the thermodynamic limit. We find a very good agreement between the experimental uniform susceptibility and the numerical results for …

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Elements Of Proximal Formative Assessment In Learners’ Discourse About Energy, Benedikt W. Harrer, Rachel E. Scherr, Michael C. Wittmann, Hunter G. Close, Brian W. Frank Jan 2012

Elements Of Proximal Formative Assessment In Learners’ Discourse About Energy, Benedikt W. Harrer, Rachel E. Scherr, Michael C. Wittmann, Hunter G. Close, Brian W. Frank

Faculty Publications

Proximal formative assessment, the just-in-time elicitation of students' ideas that informs ongoing instruction, is usually associated with the instructor in a formal classroom setting. However, the elicitation, assessment, and subsequent instruction that characterize proximal formative assessment are also seen in discourse among peers. We present a case in which secondary teachers in a professional development course at SPU are discussing energy flow in refrigerators. In this episode, a peer is invited to share her thinking (elicitation). Her idea that refrigerators move heat from a relatively cold compartment to a hotter environment is inappropriately judged as incorrect (assessment). The "instruction" (peer …

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Short-Range Correlations And Cooling Of Ultracold Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marcos Rigol Jan 2012

Short-Range Correlations And Cooling Of Ultracold Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marcos Rigol

Faculty Publications

We use determinantal quantum Monte Carlo simulations and numerical linked-cluster expansions to study thermodynamic properties and short-range spin correlations of fermions in the honeycomb lattice. We find that, at half filling and finite temperatures, nearest-neighbor spin correlations can be stronger in this lattice than in the square lattice, even in regimes where the ground state in the former is a semimetal or a spin liquid. The honeycomb lattice also exhibits a more pronounced anomalous region in the double occupancy that leads to stronger adiabatic cooling than in the square lattice. We discuss the implications of these findings for optical lattice …

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